hide new nodes behind feature flag

- "try" is not necessary / doesn't really make it clearer
- Fix incorrect name

release/scripts/startup/bl_ui/space_userpref.py

@@ -2254,6 +2254,7 @@ class USERPREF_PT_experimental_new_features(ExperimentalPanel, Panel):
                 ({"property": "use_sculpt_tools_tilt"}, "T82877"),
                 ({"property": "use_extended_asset_browser"}, ("project/view/130/", "Project Page")),
                 ({"property": "use_override_templates"}, ("T73318", "Milestone 4")),
+                ({"property": "use_geometry_nodes_fields"}, "T91274"),
             ),
         )
 

release/scripts/startup/nodeitems_builtins.py

@@ -180,6 +180,10 @@ def object_eevee_cycles_shader_nodes_poll(context):
             eevee_cycles_shader_nodes_poll(context))
 
 
+def geometry_nodes_fields_poll(context):
+    return context.preferences.experimental.use_geometry_nodes_fields
+
+
 # All standard node categories currently used in nodes.
 
 shader_node_categories = [
@@ -478,6 +482,7 @@ geometry_node_categories = [
     GeometryNodeCategory("GEO_ATTRIBUTE", "Attribute", items=[
         NodeItem("GeometryNodeAttributeRandomize"),
         NodeItem("GeometryNodeAttributeMath"),
+        NodeItem("GeometryNodeAttributeCapture", poll=geometry_nodes_fields_poll),
         NodeItem("GeometryNodeAttributeClamp"),
         NodeItem("GeometryNodeAttributeCompare"),
         NodeItem("GeometryNodeAttributeConvert"),
@@ -534,6 +539,7 @@ geometry_node_categories = [
         NodeItem("GeometryNodeJoinGeometry"),
         NodeItem("GeometryNodeSeparateComponents"),
         NodeItem("GeometryNodeRaycast"),
+        NodeItem("GeometryNodeSetPosition", poll=geometry_nodes_fields_poll),
     ]),
     GeometryNodeCategory("GEO_INPUT", "Input", items=[
         NodeItem("GeometryNodeObjectInfo"),
@@ -544,6 +550,9 @@ geometry_node_categories = [
         NodeItem("FunctionNodeInputVector"),
         NodeItem("GeometryNodeInputMaterial"),
         NodeItem("GeometryNodeIsViewport"),
+        NodeItem("GeometryNodeInputPosition", poll=geometry_nodes_fields_poll),
+        NodeItem("GeometryNodeInputIndex", poll=geometry_nodes_fields_poll),
+        NodeItem("GeometryNodeInputNormal", poll=geometry_nodes_fields_poll),
     ]),
     GeometryNodeCategory("GEO_MATERIAL", "Material", items=[
         NodeItem("GeometryNodeMaterialAssign"),

source/blender/blenkernel/BKE_anonymous_attribute.h

@@ -0,0 +1,43 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup bke
+ *
+ * An #AnonymousAttributeID is used to identify attributes that are not explicitly named.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct AnonymousAttributeID AnonymousAttributeID;
+
+AnonymousAttributeID *BKE_anonymous_attribute_id_new_weak(const char *debug_name);
+AnonymousAttributeID *BKE_anonymous_attribute_id_new_strong(const char *debug_name);
+bool BKE_anonymous_attribute_id_has_strong_references(const AnonymousAttributeID *anonymous_id);
+void BKE_anonymous_attribute_id_increment_weak(const AnonymousAttributeID *anonymous_id);
+void BKE_anonymous_attribute_id_increment_strong(const AnonymousAttributeID *anonymous_id);
+void BKE_anonymous_attribute_id_decrement_weak(const AnonymousAttributeID *anonymous_id);
+void BKE_anonymous_attribute_id_decrement_strong(const AnonymousAttributeID *anonymous_id);
+const char *BKE_anonymous_attribute_id_debug_name(const AnonymousAttributeID *anonymous_id);
+const char *BKE_anonymous_attribute_id_internal_name(const AnonymousAttributeID *anonymous_id);
+
+#ifdef __cplusplus
+}
+#endif

source/blender/blenkernel/BKE_anonymous_attribute.hh

@@ -0,0 +1,169 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+#include <atomic>
+#include <string>
+
+#include "BLI_hash.hh"
+#include "BLI_string_ref.hh"
+
+#include "BKE_anonymous_attribute.h"
+
+namespace blender::bke {
+
+/**
+ * Wrapper for #AnonymousAttributeID with RAII semantics.
+ * This class should typically not be used directly. Instead use #StrongAnonymousAttributeID or
+ * #WeakAnonymousAttributeID.
+ */
+template<bool IsStrongReference> class OwnedAnonymousAttributeID {
+ private:
+  const AnonymousAttributeID *data_ = nullptr;
+
+  template<bool OtherIsStrongReference> friend class OwnedAnonymousAttributeID;
+
+ public:
+  OwnedAnonymousAttributeID() = default;
+
+  /** Create a new anonymous attribute id. */
+  explicit OwnedAnonymousAttributeID(StringRefNull debug_name)
+  {
+    if constexpr (IsStrongReference) {
+      data_ = BKE_anonymous_attribute_id_new_strong(debug_name.c_str());
+    }
+    else {
+      data_ = BKE_anonymous_attribute_id_new_weak(debug_name.c_str());
+    }
+  }
+
+  /**
+   * This transfers ownership, so no incref is necessary.
+   * The caller has to make sure that it owned the anonymous id.
+   */
+  explicit OwnedAnonymousAttributeID(const AnonymousAttributeID *anonymous_id)
+      : data_(anonymous_id)
+  {
+  }
+
+  template<bool OtherIsStrong>
+  OwnedAnonymousAttributeID(const OwnedAnonymousAttributeID<OtherIsStrong> &other)
+  {
+    data_ = other.data_;
+    this->incref();
+  }
+
+  template<bool OtherIsStrong>
+  OwnedAnonymousAttributeID(OwnedAnonymousAttributeID<OtherIsStrong> &&other)
+  {
+    data_ = other.data_;
+    this->incref();
+    other.decref();
+    other.data_ = nullptr;
+  }
+
+  ~OwnedAnonymousAttributeID()
+  {
+    this->decref();
+  }
+
+  template<bool OtherIsStrong>
+  OwnedAnonymousAttributeID &operator=(const OwnedAnonymousAttributeID<OtherIsStrong> &other)
+  {
+    if (this == &other) {
+      return *this;
+    }
+    this->~OwnedAnonymousAttributeID();
+    new (this) OwnedAnonymousAttributeID(other);
+    return *this;
+  }
+
+  template<bool OtherIsStrong>
+  OwnedAnonymousAttributeID &operator=(OwnedAnonymousAttributeID<OtherIsStrong> &&other)
+  {
+    if (this == &other) {
+      return *this;
+    }
+    this->~OwnedAnonymousAttributeID();
+    new (this) OwnedAnonymousAttributeID(std::move(other));
+    return *this;
+  }
+
+  operator bool() const
+  {
+    return data_ != nullptr;
+  }
+
+  StringRefNull debug_name() const
+  {
+    BLI_assert(data_ != nullptr);
+    return BKE_anonymous_attribute_id_debug_name(data_);
+  }
+
+  bool has_strong_references() const
+  {
+    BLI_assert(data_ != nullptr);
+    return BKE_anonymous_attribute_id_has_strong_references(data_);
+  }
+
+  /** Extract the onwership of the currently wrapped anonymous id. */
+  const AnonymousAttributeID *extract()
+  {
+    const AnonymousAttributeID *extracted_data = data_;
+    /* Don't decref because the caller becomes the new owner. */
+    data_ = nullptr;
+    return extracted_data;
+  }
+
+  /** Get the wrapped anonymous id, without taking ownership. */
+  const AnonymousAttributeID *get() const
+  {
+    return data_;
+  }
+
+ private:
+  void incref()
+  {
+    if (data_ == nullptr) {
+      return;
+    }
+    if constexpr (IsStrongReference) {
+      BKE_anonymous_attribute_id_increment_strong(data_);
+    }
+    else {
+      BKE_anonymous_attribute_id_increment_weak(data_);
+    }
+  }
+
+  void decref()
+  {
+    if (data_ == nullptr) {
+      return;
+    }
+    if constexpr (IsStrongReference) {
+      BKE_anonymous_attribute_id_decrement_strong(data_);
+    }
+    else {
+      BKE_anonymous_attribute_id_decrement_weak(data_);
+    }
+  }
+};
+
+using StrongAnonymousAttributeID = OwnedAnonymousAttributeID<true>;
+using WeakAnonymousAttributeID = OwnedAnonymousAttributeID<false>;
+
+}  // namespace blender::bke

source/blender/blenkernel/BKE_attribute_access.hh

@@ -22,6 +22,7 @@
 #include "FN_generic_span.hh"
 #include "FN_generic_virtual_array.hh"
 
+#include "BKE_anonymous_attribute.hh"
 #include "BKE_attribute.h"
 
 #include "BLI_color.hh"
@@ -29,6 +30,81 @@
 #include "BLI_float3.hh"
 #include "BLI_function_ref.hh"
 
+namespace blender::bke {
+
+/**
+ * Identifies an attribute that is either named or anonymous.
+ * It does not own the identifier, so it is just a reference.
+ */
+class AttributeIDRef {
+ private:
+  StringRef name_;
+  const AnonymousAttributeID *anonymous_id_ = nullptr;
+
+ public:
+  AttributeIDRef() = default;
+
+  AttributeIDRef(StringRef name) : name_(name)
+  {
+  }
+
+  AttributeIDRef(StringRefNull name) : name_(name)
+  {
+  }
+
+  AttributeIDRef(const char *name) : name_(name)
+  {
+  }
+
+  AttributeIDRef(const std::string &name) : name_(name)
+  {
+  }
+
+  /* The anonymous id is only borrowed, the caller has to keep a reference to it. */
+  AttributeIDRef(const AnonymousAttributeID *anonymous_id) : anonymous_id_(anonymous_id)
+  {
+  }
+
+  operator bool() const
+  {
+    return this->is_named() || this->is_anonymous();
+  }
+
+  friend bool operator==(const AttributeIDRef &a, const AttributeIDRef &b)
+  {
+    return a.anonymous_id_ == b.anonymous_id_ && a.name_ == b.name_;
+  }
+
+  uint64_t hash() const
+  {
+    return get_default_hash_2(name_, anonymous_id_);
+  }
+
+  bool is_named() const
+  {
+    return !name_.is_empty();
+  }
+
+  bool is_anonymous() const
+  {
+    return anonymous_id_ != nullptr;
+  }
+
+  StringRef name() const
+  {
+    BLI_assert(this->is_named());
+    return name_;
+  }
+
+  const AnonymousAttributeID &anonymous_id() const
+  {
+    BLI_assert(this->is_anonymous());
+    return *anonymous_id_;
+  }
+};
+
+}  // namespace blender::bke
+
 /**
  * Contains information about an attribute in a geometry component.
  * More information can be added in the future. E.g. whether the attribute is builtin and how it is
@@ -104,8 +180,8 @@ struct AttributeInitMove : public AttributeInit {
 };
 
 /* Returns false when the iteration should be stopped. */
-using AttributeForeachCallback = blender::FunctionRef<bool(blender::StringRefNull attribute_name,
-                                                           const AttributeMetaData &meta_data)>;
+using AttributeForeachCallback = blender::FunctionRef<bool(
+    const blender::bke::AttributeIDRef &attribute_id, const AttributeMetaData &meta_data)>;
 
 namespace blender::bke {
 
@@ -333,26 +409,28 @@ class CustomDataAttributes {
 
   void reallocate(const int size);
 
-  std::optional<blender::fn::GSpan> get_for_read(const blender::StringRef name) const;
+  std::optional<blender::fn::GSpan> get_for_read(const AttributeIDRef &attribute_id) const;
 
-  blender::fn::GVArrayPtr get_for_read(const StringRef name,
+  blender::fn::GVArrayPtr get_for_read(const AttributeIDRef &attribute_id,
                                        const CustomDataType data_type,
                                        const void *default_value) const;
 
   template<typename T>
-  blender::fn::GVArray_Typed<T> get_for_read(const blender::StringRef name,
+  blender::fn::GVArray_Typed<T> get_for_read(const AttributeIDRef &attribute_id,
                                              const T &default_value) const
   {
     const blender::fn::CPPType &cpp_type = blender::fn::CPPType::get<T>();
     const CustomDataType type = blender::bke::cpp_type_to_custom_data_type(cpp_type);
-    GVArrayPtr varray = this->get_for_read(name, type, &default_value);
+    GVArrayPtr varray = this->get_for_read(attribute_id, type, &default_value);
     return blender::fn::GVArray_Typed<T>(std::move(varray));
   }
 
-  std::optional<blender::fn::GMutableSpan> get_for_write(const blender::StringRef name);
-  bool create(const blender::StringRef name, const CustomDataType data_type);
-  bool create_by_move(const blender::StringRef name, const CustomDataType data_type, void *buffer);
-  bool remove(const blender::StringRef name);
+  std::optional<blender::fn::GMutableSpan> get_for_write(const AttributeIDRef &attribute_id);
+  bool create(const AttributeIDRef &attribute_id, const CustomDataType data_type);
+  bool create_by_move(const AttributeIDRef &attribute_id,
+                      const CustomDataType data_type,
+                      void *buffer);
+  bool remove(const AttributeIDRef &attribute_id);
 
   bool foreach_attribute(const AttributeForeachCallback callback,
                          const AttributeDomain domain) const;

source/blender/blenkernel/BKE_customdata.h

@@ -33,6 +33,7 @@
 extern "C" {
 #endif
 
+struct AnonymousAttributeID;
 struct BMesh;
 struct BlendDataReader;
 struct BlendWriter;
@@ -193,6 +194,12 @@ void *CustomData_add_layer_named(struct CustomData *data,
                                  void *layer,
                                  int totelem,
                                  const char *name);
+void *CustomData_add_layer_anonymous(struct CustomData *data,
+                                     int type,
+                                     eCDAllocType alloctype,
+                                     void *layer,
+                                     int totelem,
+                                     const struct AnonymousAttributeID *anonymous_id);
 
 /* frees the active or first data layer with the give type.
  * returns 1 on success, 0 if no layer with the given type is found
@@ -231,6 +238,11 @@ void *CustomData_duplicate_referenced_layer_named(struct CustomData *data,
                                                   const int type,
                                                   const char *name,
                                                   const int totelem);
+void *CustomData_duplicate_referenced_layer_anonymous(
+    CustomData *data,
+    const int type,
+    const struct AnonymousAttributeID *anonymous_id,
+    const int totelem);
 bool CustomData_is_referenced_layer(struct CustomData *data, int type);
 
 /* Duplicate all the layers with flag NOFREE, and remove the flag from duplicated layers. */

source/blender/blenkernel/BKE_geometry_set.hh

@@ -31,9 +31,12 @@
 #include "BLI_user_counter.hh"
 #include "BLI_vector_set.hh"
 
+#include "BKE_anonymous_attribute.hh"
 #include "BKE_attribute_access.hh"
 #include "BKE_geometry_set.h"
 
+#include "FN_field.hh"
+
 struct Collection;
 struct Curve;
 struct CurveEval;
@@ -88,11 +91,11 @@ class GeometryComponent {
   GeometryComponentType type() const;
 
   /* Return true when any attribute with this name exists, including built in attributes. */
-  bool attribute_exists(const blender::StringRef attribute_name) const;
+  bool attribute_exists(const blender::bke::AttributeIDRef &attribute_id) const;
 
   /* Return the data type and domain of an attribute with the given name if it exists. */
   std::optional<AttributeMetaData> attribute_get_meta_data(
-      const blender::StringRef attribute_name) const;
+      const blender::bke::AttributeIDRef &attribute_id) const;
 
   /* Returns true when the geometry component supports this attribute domain. */
   bool attribute_domain_supported(const AttributeDomain domain) const;
@@ -104,12 +107,12 @@ class GeometryComponent {
   /* Get read-only access to the highest priority attribute with the given name.
    * Returns null if the attribute does not exist. */
   blender::bke::ReadAttributeLookup attribute_try_get_for_read(
-      const blender::StringRef attribute_name) const;
+      const blender::bke::AttributeIDRef &attribute_id) const;
 
   /* Get read and write access to the highest priority attribute with the given name.
    * Returns null if the attribute does not exist. */
   blender::bke::WriteAttributeLookup attribute_try_get_for_write(
-      const blender::StringRef attribute_name);
+      const blender::bke::AttributeIDRef &attribute_id);
 
   /* Get a read-only attribute for the domain based on the given attribute. This can be used to
    * interpolate from one domain to another.
@@ -120,10 +123,10 @@ class GeometryComponent {
       const AttributeDomain to_domain) const;
 
   /* Returns true when the attribute has been deleted. */
-  bool attribute_try_delete(const blender::StringRef attribute_name);
+  bool attribute_try_delete(const blender::bke::AttributeIDRef &attribute_id);
 
   /* Returns true when the attribute has been created. */
-  bool attribute_try_create(const blender::StringRef attribute_name,
+  bool attribute_try_create(const blender::bke::AttributeIDRef &attribute_id,
                             const AttributeDomain domain,
                             const CustomDataType data_type,
                             const AttributeInit &initializer);
@@ -133,7 +136,7 @@ class GeometryComponent {
   bool attribute_try_create_builtin(const blender::StringRef attribute_name,
                                     const AttributeInit &initializer);
 
-  blender::Set<std::string> attribute_names() const;
+  blender::Set<blender::bke::AttributeIDRef> attribute_ids() const;
   bool attribute_foreach(const AttributeForeachCallback callback) const;
 
   virtual bool is_empty() const;
@@ -142,7 +145,7 @@ class GeometryComponent {
    * Returns null when the attribute does not exist or cannot be converted to the requested domain
    * and data type. */
   std::unique_ptr<blender::fn::GVArray> attribute_try_get_for_read(
-      const blender::StringRef attribute_name,
+      const blender::bke::AttributeIDRef &attribute_id,
       const AttributeDomain domain,
       const CustomDataType data_type) const;
 
@@ -150,18 +153,18 @@ class GeometryComponent {
    * left unchanged. Returns null when the attribute does not exist or cannot be adapted to the
    * requested domain. */
   std::unique_ptr<blender::fn::GVArray> attribute_try_get_for_read(
-      const blender::StringRef attribute_name, const AttributeDomain domain) const;
+      const blender::bke::AttributeIDRef &attribute_id, const AttributeDomain domain) const;
 
   /* Get a virtual array to read data of an attribute with the given data type. The domain is
    * left unchanged. Returns null when the attribute does not exist or cannot be converted to the
    * requested data type. */
   blender::bke::ReadAttributeLookup attribute_try_get_for_read(
-      const blender::StringRef attribute_name, const CustomDataType data_type) const;
+      const blender::bke::AttributeIDRef &attribute_id, const CustomDataType data_type) const;
 
   /* Get a virtual array to read the data of an attribute. If that is not possible, the returned
    * virtual array will contain a default value. This never returns null. */
   std::unique_ptr<blender::fn::GVArray> attribute_get_for_read(
-      const blender::StringRef attribute_name,
+      const blender::bke::AttributeIDRef &attribute_id,
       const AttributeDomain domain,
       const CustomDataType data_type,
       const void *default_value = nullptr) const;
@@ -169,14 +172,15 @@ class GeometryComponent {
   /* Should be used instead of the method above when the requested data type is known at compile
    * time for better type safety. */
   template<typename T>
-  blender::fn::GVArray_Typed<T> attribute_get_for_read(const blender::StringRef attribute_name,
-                                                       const AttributeDomain domain,
-                                                       const T &default_value) const
+  blender::fn::GVArray_Typed<T> attribute_get_for_read(
+      const blender::bke::AttributeIDRef &attribute_id,
+      const AttributeDomain domain,
+      const T &default_value) const
   {
     const blender::fn::CPPType &cpp_type = blender::fn::CPPType::get<T>();
     const CustomDataType type = blender::bke::cpp_type_to_custom_data_type(cpp_type);
     std::unique_ptr varray = this->attribute_get_for_read(
-        attribute_name, domain, type, &default_value);
+        attribute_id, domain, type, &default_value);
     return blender::fn::GVArray_Typed<T>(std::move(varray));
   }
 
@@ -191,7 +195,7 @@ class GeometryComponent {
    *   is created that will overwrite the existing attribute in the end.
    */
   blender::bke::OutputAttribute attribute_try_get_for_output(
-      const blender::StringRef attribute_name,
+      const blender::bke::AttributeIDRef &attribute_id,
       const AttributeDomain domain,
       const CustomDataType data_type,
       const void *default_value = nullptr);
@@ -200,28 +204,30 @@ class GeometryComponent {
    * attributes are not read, i.e. the attribute is used only for output. Since values are not read
    * from this attribute, no default value is necessary. */
   blender::bke::OutputAttribute attribute_try_get_for_output_only(
-      const blender::StringRef attribute_name,
+      const blender::bke::AttributeIDRef &attribute_id,
       const AttributeDomain domain,
       const CustomDataType data_type);
 
   /* Statically typed method corresponding to the equally named generic one. */
   template<typename T>
   blender::bke::OutputAttribute_Typed<T> attribute_try_get_for_output(
-      const blender::StringRef attribute_name, const AttributeDomain domain, const T default_value)
+      const blender::bke::AttributeIDRef &attribute_id,
+      const AttributeDomain domain,
+      const T default_value)
   {
     const blender::fn::CPPType &cpp_type = blender::fn::CPPType::get<T>();
     const CustomDataType data_type = blender::bke::cpp_type_to_custom_data_type(cpp_type);
-    return this->attribute_try_get_for_output(attribute_name, domain, data_type, &default_value);
+    return this->attribute_try_get_for_output(attribute_id, domain, data_type, &default_value);
   }
 
   /* Statically typed method corresponding to the equally named generic one. */
   template<typename T>
   blender::bke::OutputAttribute_Typed<T> attribute_try_get_for_output_only(
-      const blender::StringRef attribute_name, const AttributeDomain domain)
+      const blender::bke::AttributeIDRef &attribute_id, const AttributeDomain domain)
   {
     const blender::fn::CPPType &cpp_type = blender::fn::CPPType::get<T>();
     const CustomDataType data_type = blender::bke::cpp_type_to_custom_data_type(cpp_type);
-    return this->attribute_try_get_for_output_only(attribute_name, domain, data_type);
+    return this->attribute_try_get_for_output_only(attribute_id, domain, data_type);
   }
 
  private:
@@ -616,3 +622,69 @@ class VolumeComponent : public GeometryComponent {
 
   static constexpr inline GeometryComponentType static_type = GEO_COMPONENT_TYPE_VOLUME;
 };
+
+namespace blender::bke {
+
+class GeometryComponentFieldContext : public fn::FieldContext {
+ private:
+  const GeometryComponent &component_;
+  const AttributeDomain domain_;
+
+ public:
+  GeometryComponentFieldContext(const GeometryComponent &component, const AttributeDomain domain)
+      : component_(component), domain_(domain)
+  {
+  }
+
+  const GeometryComponent &geometry_component() const
+  {
+    return component_;
+  }
+
+  AttributeDomain domain() const
+  {
+    return domain_;
+  }
+};
+
+class AttributeFieldInput : public fn::FieldInput {
+ private:
+  std::string name_;
+
+ public:
+  AttributeFieldInput(std::string name, const CPPType &type)
+      : fn::FieldInput(type, name), name_(std::move(name))
+  {
+  }
+
+  const GVArray *get_varray_for_context(const fn::FieldContext &context,
+                                        IndexMask mask,
+                                        ResourceScope &scope) const override;
+
+  uint64_t hash() const override;
+  bool is_equal_to(const fn::FieldNode &other) const override;
+};
+
+class AnonymousAttributeFieldInput : public fn::FieldInput {
+ private:
+  /**
+   * A strong reference is required to make sure that the referenced attribute is not removed
+   * automatically.
+   */
+  StrongAnonymousAttributeID anonymous_id_;
+
+ public:
+  AnonymousAttributeFieldInput(StrongAnonymousAttributeID anonymous_id, const CPPType &type)
+      : fn::FieldInput(type, anonymous_id.debug_name()), anonymous_id_(std::move(anonymous_id))
+  {
+  }
+
+  const GVArray *get_varray_for_context(const fn::FieldContext &context,
+                                        IndexMask mask,
+                                        ResourceScope &scope) const override;
+
+  uint64_t hash() const override;
+  bool is_equal_to(const fn::FieldNode &other) const override;
+};
+
+}  // namespace blender::bke

source/blender/blenkernel/BKE_geometry_set_instances.hh

@@ -59,9 +59,10 @@ struct AttributeKind {
  * will contain the highest complexity data type and the highest priority domain among every
  * attribute with the given name on all of the input components.
  */
-void geometry_set_gather_instances_attribute_info(Span<GeometryInstanceGroup> set_groups,
-                                                  Span<GeometryComponentType> component_types,
-                                                  const Set<std::string> &ignored_attributes,
-                                                  Map<std::string, AttributeKind> &r_attributes);
+void geometry_set_gather_instances_attribute_info(
+    Span<GeometryInstanceGroup> set_groups,
+    Span<GeometryComponentType> component_types,
+    const Set<std::string> &ignored_attributes,
+    Map<AttributeIDRef, AttributeKind> &r_attributes);
 
 }  // namespace blender::bke

source/blender/blenkernel/BKE_node.h

@@ -1484,6 +1484,11 @@ int ntreeTexExecTree(struct bNodeTree *ntree,
 #define GEO_NODE_CURVE_SPLINE_TYPE 1073
 #define GEO_NODE_CURVE_SELECT_HANDLES 1074
 #define GEO_NODE_CURVE_FILL 1075
+#define GEO_NODE_INPUT_POSITION 1076
+#define GEO_NODE_SET_POSITION 1077
+#define GEO_NODE_INPUT_INDEX 1078
+#define GEO_NODE_INPUT_NORMAL 1079
+#define GEO_NODE_ATTRIBUTE_CAPTURE 1080
 
 /** \} */
 

source/blender/blenkernel/CMakeLists.txt

@@ -76,6 +76,7 @@ set(SRC
   intern/anim_path.c
   intern/anim_sys.c
   intern/anim_visualization.c
+  intern/anonymous_attribute.cc
   intern/appdir.c
   intern/armature.c
   intern/armature_deform.c
@@ -295,6 +296,8 @@ set(SRC
   BKE_anim_path.h
   BKE_anim_visualization.h
   BKE_animsys.h
+  BKE_anonymous_attribute.h
+  BKE_anonymous_attribute.hh
   BKE_appdir.h
   BKE_armature.h
   BKE_armature.hh

source/blender/blenkernel/intern/anonymous_attribute.cc

@@ -0,0 +1,118 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "BKE_anonymous_attribute.hh"
+
+using namespace blender::bke;
+
+/**
+ * A struct that identifies an attribute. It's lifetime is managed by an atomic reference count.
+ *
+ * Additionally, this struct can be strongly or weakly owned. The difference is that strong
+ * ownership means that attributes with this id will be kept around. Weak ownership just makes sure
+ * that the struct itself stays alive, but corresponding attributes might still be removed
+ * automatically.
+ */
+struct AnonymousAttributeID {
+  /**
+   * Total number of references to this attribute id. Once this reaches zero, the struct can be
+   * freed. This includes strong and weak references.
+   */
+  mutable std::atomic<int> refcount_tot = 0;
+
+  /**
+   * Number of strong references to this attribute id. When this is zero, the corresponding
+   * attributes can be removed from geometries automatically.
+   */
+  mutable std::atomic<int> refcount_strong = 0;
+
+  /**
+   * Only used to identify this struct in a debugging session.
+   */
+  std::string debug_name;
+
+  /**
+   * Unique name of the this attribute id during the current session.
+   */
+  std::string internal_name;
+};
+
+/** Every time this function is called, it outputs a different name. */
+static std::string get_new_internal_name()
+{
+  static std::atomic<int> index = 0;
+  const int next_index = index.fetch_add(1);
+  return "anonymous_attribute_" + std::to_string(next_index);
+}
+
+AnonymousAttributeID *BKE_anonymous_attribute_id_new_weak(const char *debug_name)
+{
+  AnonymousAttributeID *anonymous_id = new AnonymousAttributeID();
+  anonymous_id->debug_name = debug_name;
+  anonymous_id->internal_name = get_new_internal_name();
+  anonymous_id->refcount_tot.store(1);
+  return anonymous_id;
+}
+
+AnonymousAttributeID *BKE_anonymous_attribute_id_new_strong(const char *debug_name)
+{
+  AnonymousAttributeID *anonymous_id = new AnonymousAttributeID();
+  anonymous_id->debug_name = debug_name;
+  anonymous_id->internal_name = get_new_internal_name();
+  anonymous_id->refcount_tot.store(1);
+  anonymous_id->refcount_strong.store(1);
+  return anonymous_id;
+}
+
+bool BKE_anonymous_attribute_id_has_strong_references(const AnonymousAttributeID *anonymous_id)
+{
+  return anonymous_id->refcount_strong.load() >= 1;
+}
+
+void BKE_anonymous_attribute_id_increment_weak(const AnonymousAttributeID *anonymous_id)
+{
+  anonymous_id->refcount_tot.fetch_add(1);
+}
+
+void BKE_anonymous_attribute_id_increment_strong(const AnonymousAttributeID *anonymous_id)
+{
+  anonymous_id->refcount_tot.fetch_add(1);
+  anonymous_id->refcount_strong.fetch_add(1);
+}
+
+void BKE_anonymous_attribute_id_decrement_weak(const AnonymousAttributeID *anonymous_id)
+{
+  const int new_refcount = anonymous_id->refcount_tot.fetch_sub(1) - 1;
+  if (new_refcount == 0) {
+    delete anonymous_id;
+  }
+}
+
+void BKE_anonymous_attribute_id_decrement_strong(const AnonymousAttributeID *anonymous_id)
+{
+  anonymous_id->refcount_strong.fetch_sub(1);
+  BKE_anonymous_attribute_id_decrement_weak(anonymous_id);
+}
+
+const char *BKE_anonymous_attribute_id_debug_name(const AnonymousAttributeID *anonymous_id)
+{
+  return anonymous_id->debug_name.c_str();
+}
+
+const char *BKE_anonymous_attribute_id_internal_name(const AnonymousAttributeID *anonymous_id)
+{
+  return anonymous_id->internal_name.c_str();
+}

source/blender/blenkernel/intern/attribute_access.cc

@@ -44,6 +44,8 @@ using blender::float3;
 using blender::Set;
 using blender::StringRef;
 using blender::StringRefNull;
+using blender::bke::AttributeIDRef;
+using blender::bke::OutputAttribute;
 using blender::fn::GMutableSpan;
 using blender::fn::GSpan;
 using blender::fn::GVArray_For_GSpan;
@@ -334,8 +336,20 @@ bool BuiltinCustomDataLayerProvider::exists(const GeometryComponent &component)
   return data != nullptr;
 }
 
+static bool custom_data_layer_matches_attribute_id(const CustomDataLayer &layer,
+                                                   const AttributeIDRef &attribute_id)
+{
+  if (!attribute_id) {
+    return false;
+  }
+  if (attribute_id.is_anonymous()) {
+    return layer.anonymous_id == &attribute_id.anonymous_id();
+  }
+  return layer.name == attribute_id.name();
+}
+
 ReadAttributeLookup CustomDataAttributeProvider::try_get_for_read(
-    const GeometryComponent &component, const StringRef attribute_name) const
+    const GeometryComponent &component, const AttributeIDRef &attribute_id) const
 {
   const CustomData *custom_data = custom_data_access_.get_const_custom_data(component);
   if (custom_data == nullptr) {
@@ -343,7 +357,7 @@ ReadAttributeLookup CustomDataAttributeProvider::try_get_for_read(
   }
   const int domain_size = component.attribute_domain_size(domain_);
   for (const CustomDataLayer &layer : Span(custom_data->layers, custom_data->totlayer)) {
-    if (layer.name != attribute_name) {
+    if (!custom_data_layer_matches_attribute_id(layer, attribute_id)) {
       continue;
     }
     const CustomDataType data_type = (CustomDataType)layer.type;
@@ -368,7 +382,7 @@ ReadAttributeLookup CustomDataAttributeProvider::try_get_for_read(
 }
 
 WriteAttributeLookup CustomDataAttributeProvider::try_get_for_write(
-    GeometryComponent &component, const StringRef attribute_name) const
+    GeometryComponent &component, const AttributeIDRef &attribute_id) const
 {
   CustomData *custom_data = custom_data_access_.get_custom_data(component);
   if (custom_data == nullptr) {
@@ -376,10 +390,17 @@ WriteAttributeLookup CustomDataAttributeProvider::try_get_for_write(
   }
   const int domain_size = component.attribute_domain_size(domain_);
   for (CustomDataLayer &layer : MutableSpan(custom_data->layers, custom_data->totlayer)) {
-    if (layer.name != attribute_name) {
+    if (!custom_data_layer_matches_attribute_id(layer, attribute_id)) {
       continue;
     }
-    CustomData_duplicate_referenced_layer_named(custom_data, layer.type, layer.name, domain_size);
+    if (attribute_id.is_named()) {
+      CustomData_duplicate_referenced_layer_named(
+          custom_data, layer.type, layer.name, domain_size);
+    }
+    else {
+      CustomData_duplicate_referenced_layer_anonymous(
+          custom_data, layer.type, &attribute_id.anonymous_id(), domain_size);
+    }
     const CustomDataType data_type = (CustomDataType)layer.type;
     switch (data_type) {
       case CD_PROP_FLOAT:
@@ -402,7 +423,7 @@ WriteAttributeLookup CustomDataAttributeProvider::try_get_for_write(
 }
 
 bool CustomDataAttributeProvider::try_delete(GeometryComponent &component,
-                                             const StringRef attribute_name) const
+                                             const AttributeIDRef &attribute_id) const
 {
   CustomData *custom_data = custom_data_access_.get_custom_data(component);
   if (custom_data == nullptr) {
@@ -411,7 +432,8 @@ bool CustomDataAttributeProvider::try_delete(GeometryComponent &component,
   const int domain_size = component.attribute_domain_size(domain_);
   for (const int i : IndexRange(custom_data->totlayer)) {
     const CustomDataLayer &layer = custom_data->layers[i];
-    if (this->type_is_supported((CustomDataType)layer.type) && layer.name == attribute_name) {
+    if (this->type_is_supported((CustomDataType)layer.type) &&
+        custom_data_layer_matches_attribute_id(layer, attribute_id)) {
       CustomData_free_layer(custom_data, layer.type, domain_size, i);
       return true;
     }
@@ -419,24 +441,39 @@ bool CustomDataAttributeProvider::try_delete(GeometryComponent &component,
   return false;
 }
 
-static bool add_named_custom_data_layer_from_attribute_init(const StringRef attribute_name,
-                                                            CustomData &custom_data,
-                                                            const CustomDataType data_type,
-                                                            const int domain_size,
-                                                            const AttributeInit &initializer)
+static void *add_generic_custom_data_layer(CustomData &custom_data,
+                                           const CustomDataType data_type,
+                                           const eCDAllocType alloctype,
+                                           void *layer_data,
+                                           const int domain_size,
+                                           const AttributeIDRef &attribute_id)
 {
-  char attribute_name_c[MAX_NAME];
-  attribute_name.copy(attribute_name_c);
+  if (attribute_id.is_named()) {
+    char attribute_name_c[MAX_NAME];
+    attribute_id.name().copy(attribute_name_c);
+    return CustomData_add_layer_named(
+        &custom_data, data_type, CD_DEFAULT, nullptr, domain_size, attribute_name_c);
+  }
+  const AnonymousAttributeID &anonymous_id = attribute_id.anonymous_id();
+  return CustomData_add_layer_anonymous(
+      &custom_data, data_type, alloctype, layer_data, domain_size, &anonymous_id);
+}
 
+static bool add_custom_data_layer_from_attribute_init(const AttributeIDRef &attribute_id,
+                                                      CustomData &custom_data,
+                                                      const CustomDataType data_type,
+                                                      const int domain_size,
+                                                      const AttributeInit &initializer)
+{
   switch (initializer.type) {
     case AttributeInit::Type::Default: {
-      void *data = CustomData_add_layer_named(
-          &custom_data, data_type, CD_DEFAULT, nullptr, domain_size, attribute_name_c);
+      void *data = add_generic_custom_data_layer(
+          custom_data, data_type, CD_DEFAULT, nullptr, domain_size, attribute_id);
       return data != nullptr;
     }
     case AttributeInit::Type::VArray: {
-      void *data = CustomData_add_layer_named(
-          &custom_data, data_type, CD_DEFAULT, nullptr, domain_size, attribute_name_c);
+      void *data = add_generic_custom_data_layer(
+          custom_data, data_type, CD_DEFAULT, nullptr, domain_size, attribute_id);
       if (data == nullptr) {
         return false;
       }
@@ -446,8 +483,8 @@ static bool add_named_custom_data_layer_from_attribute_init(const StringRef attr
     }
     case AttributeInit::Type::MoveArray: {
       void *source_data = static_cast<const AttributeInitMove &>(initializer).data;
-      void *data = CustomData_add_layer_named(
-          &custom_data, data_type, CD_ASSIGN, source_data, domain_size, attribute_name_c);
+      void *data = add_generic_custom_data_layer(
+          custom_data, data_type, CD_ASSIGN, source_data, domain_size, attribute_id);
       if (data == nullptr) {
         MEM_freeN(source_data);
         return false;
@@ -461,7 +498,7 @@ static bool add_named_custom_data_layer_from_attribute_init(const StringRef attr
 }
 
 bool CustomDataAttributeProvider::try_create(GeometryComponent &component,
-                                             const StringRef attribute_name,
+                                             const AttributeIDRef &attribute_id,
                                              const AttributeDomain domain,
                                              const CustomDataType data_type,
                                              const AttributeInit &initializer) const
@@ -477,13 +514,13 @@ bool CustomDataAttributeProvider::try_create(GeometryComponent &component,
     return false;
   }
   for (const CustomDataLayer &layer : Span(custom_data->layers, custom_data->totlayer)) {
-    if (layer.name == attribute_name) {
+    if (custom_data_layer_matches_attribute_id(layer, attribute_id)) {
       return false;
     }
   }
   const int domain_size = component.attribute_domain_size(domain_);
-  add_named_custom_data_layer_from_attribute_init(
-      attribute_name, *custom_data, data_type, domain_size, initializer);
+  add_custom_data_layer_from_attribute_init(
+      attribute_id, *custom_data, data_type, domain_size, initializer);
   return true;
 }
 
@@ -498,7 +535,14 @@ bool CustomDataAttributeProvider::foreach_attribute(const GeometryComponent &com
     const CustomDataType data_type = (CustomDataType)layer.type;
     if (this->type_is_supported(data_type)) {
       AttributeMetaData meta_data{domain_, data_type};
-      if (!callback(layer.name, meta_data)) {
+      AttributeIDRef attribute_id;
+      if (layer.anonymous_id != nullptr) {
+        attribute_id = layer.anonymous_id;
+      }
+      else {
+        attribute_id = layer.name;
+      }
+      if (!callback(attribute_id, meta_data)) {
         return false;
       }
     }
@@ -507,7 +551,7 @@ bool CustomDataAttributeProvider::foreach_attribute(const GeometryComponent &com
 }
 
 ReadAttributeLookup NamedLegacyCustomDataProvider::try_get_for_read(
-    const GeometryComponent &component, const StringRef attribute_name) const
+    const GeometryComponent &component, const AttributeIDRef &attribute_id) const
 {
   const CustomData *custom_data = custom_data_access_.get_const_custom_data(component);
   if (custom_data == nullptr) {
@@ -515,7 +559,7 @@ ReadAttributeLookup NamedLegacyCustomDataProvider::try_get_for_read(
   }
   for (const CustomDataLayer &layer : Span(custom_data->layers, custom_data->totlayer)) {
     if (layer.type == stored_type_) {
-      if (layer.name == attribute_name) {
+      if (custom_data_layer_matches_attribute_id(layer, attribute_id)) {
         const int domain_size = component.attribute_domain_size(domain_);
         return {as_read_attribute_(layer.data, domain_size), domain_};
       }
@@ -525,7 +569,7 @@ ReadAttributeLookup NamedLegacyCustomDataProvider::try_get_for_read(
 }
 
 WriteAttributeLookup NamedLegacyCustomDataProvider::try_get_for_write(
-    GeometryComponent &component, const StringRef attribute_name) const
+    GeometryComponent &component, const AttributeIDRef &attribute_id) const
 {
   CustomData *custom_data = custom_data_access_.get_custom_data(component);
   if (custom_data == nullptr) {
@@ -533,7 +577,7 @@ WriteAttributeLookup NamedLegacyCustomDataProvider::try_get_for_write(
   }
   for (CustomDataLayer &layer : MutableSpan(custom_data->layers, custom_data->totlayer)) {
     if (layer.type == stored_type_) {
-      if (layer.name == attribute_name) {
+      if (custom_data_layer_matches_attribute_id(layer, attribute_id)) {
         const int domain_size = component.attribute_domain_size(domain_);
         void *data_old = layer.data;
         void *data_new = CustomData_duplicate_referenced_layer_named(
@@ -549,7 +593,7 @@ WriteAttributeLookup NamedLegacyCustomDataProvider::try_get_for_write(
 }
 
 bool NamedLegacyCustomDataProvider::try_delete(GeometryComponent &component,
-                                               const StringRef attribute_name) const
+                                               const AttributeIDRef &attribute_id) const
 {
   CustomData *custom_data = custom_data_access_.get_custom_data(component);
   if (custom_data == nullptr) {
@@ -558,7 +602,7 @@ bool NamedLegacyCustomDataProvider::try_delete(GeometryComponent &component,
   for (const int i : IndexRange(custom_data->totlayer)) {
     const CustomDataLayer &layer = custom_data->layers[i];
     if (layer.type == stored_type_) {
-      if (layer.name == attribute_name) {
+      if (custom_data_layer_matches_attribute_id(layer, attribute_id)) {
         const int domain_size = component.attribute_domain_size(domain_);
         CustomData_free_layer(custom_data, stored_type_, domain_size, i);
         custom_data_access_.update_custom_data_pointers(component);
@@ -627,11 +671,11 @@ CustomDataAttributes &CustomDataAttributes::operator=(const CustomDataAttributes
   return *this;
 }
 
-std::optional<GSpan> CustomDataAttributes::get_for_read(const StringRef name) const
+std::optional<GSpan> CustomDataAttributes::get_for_read(const AttributeIDRef &attribute_id) const
 {
   BLI_assert(size_ != 0);
   for (const CustomDataLayer &layer : Span(data.layers, data.totlayer)) {
-    if (layer.name == name) {
+    if (custom_data_layer_matches_attribute_id(layer, attribute_id)) {
       const CPPType *cpp_type = custom_data_type_to_cpp_type((CustomDataType)layer.type);
       BLI_assert(cpp_type != nullptr);
       return GSpan(*cpp_type, layer.data, size_);
@@ -645,13 +689,13 @@ std::optional<GSpan> CustomDataAttributes::get_for_read(const StringRef name) co
  * value if the attribute doesn't exist. If no default value is provided, the default value for the
  * type will be used.
  */
-GVArrayPtr CustomDataAttributes::get_for_read(const StringRef name,
+GVArrayPtr CustomDataAttributes::get_for_read(const AttributeIDRef &attribute_id,
                                               const CustomDataType data_type,
                                               const void *default_value) const
 {
   const CPPType *type = blender::bke::custom_data_type_to_cpp_type(data_type);
 
-  std::optional<GSpan> attribute = this->get_for_read(name);
+  std::optional<GSpan> attribute = this->get_for_read(attribute_id);
   if (!attribute) {
     const int domain_size = this->size_;
     return std::make_unique<GVArray_For_SingleValue>(
@@ -666,12 +710,12 @@ GVArrayPtr CustomDataAttributes::get_for_read(const StringRef name,
   return conversions.try_convert(std::make_unique<GVArray_For_GSpan>(*attribute), *type);
 }
 
-std::optional<GMutableSpan> CustomDataAttributes::get_for_write(const StringRef name)
+std::optional<GMutableSpan> CustomDataAttributes::get_for_write(const AttributeIDRef &attribute_id)
 {
   /* If this assert hits, it most likely means that #reallocate was not called at some point. */
   BLI_assert(size_ != 0);
   for (CustomDataLayer &layer : MutableSpan(data.layers, data.totlayer)) {
-    if (layer.name == name) {
+    if (custom_data_layer_matches_attribute_id(layer, attribute_id)) {
       const CPPType *cpp_type = custom_data_type_to_cpp_type((CustomDataType)layer.type);
       BLI_assert(cpp_type != nullptr);
       return GMutableSpan(*cpp_type, layer.data, size_);
@@ -680,30 +724,29 @@ std::optional<GMutableSpan> CustomDataAttributes::get_for_write(const StringRef
   return {};
 }
 
-bool CustomDataAttributes::create(const StringRef name, const CustomDataType data_type)
+bool CustomDataAttributes::create(const AttributeIDRef &attribute_id,
+                                  const CustomDataType data_type)
 {
-  char name_c[MAX_NAME];
-  name.copy(name_c);
-  void *result = CustomData_add_layer_named(&data, data_type, CD_DEFAULT, nullptr, size_, name_c);
+  void *result = add_generic_custom_data_layer(
+      data, data_type, CD_DEFAULT, nullptr, size_, attribute_id);
   return result != nullptr;
 }
 
-bool CustomDataAttributes::create_by_move(const blender::StringRef name,
+bool CustomDataAttributes::create_by_move(const AttributeIDRef &attribute_id,
                                           const CustomDataType data_type,
                                           void *buffer)
 {
-  char name_c[MAX_NAME];
-  name.copy(name_c);
-  void *result = CustomData_add_layer_named(&data, data_type, CD_ASSIGN, buffer, size_, name_c);
+  void *result = add_generic_custom_data_layer(
+      data, data_type, CD_ASSIGN, buffer, size_, attribute_id);
   return result != nullptr;
 }
 
-bool CustomDataAttributes::remove(const blender::StringRef name)
+bool CustomDataAttributes::remove(const AttributeIDRef &attribute_id)
 {
   bool result = false;
   for (const int i : IndexRange(data.totlayer)) {
     const CustomDataLayer &layer = data.layers[i];
-    if (layer.name == name) {
+    if (custom_data_layer_matches_attribute_id(layer, attribute_id)) {
       CustomData_free_layer(&data, layer.type, size_, i);
       result = true;
     }
@@ -722,7 +765,14 @@ bool CustomDataAttributes::foreach_attribute(const AttributeForeachCallback call
 {
   for (const CustomDataLayer &layer : Span(data.layers, data.totlayer)) {
     AttributeMetaData meta_data{domain, (CustomDataType)layer.type};
-    if (!callback(layer.name, meta_data)) {
+    AttributeIDRef attribute_id;
+    if (layer.anonymous_id != nullptr) {
+      attribute_id = layer.anonymous_id;
+    }
+    else {
+      attribute_id = layer.name;
+    }
+    if (!callback(attribute_id, meta_data)) {
       return false;
     }
   }
@@ -766,21 +816,23 @@ bool GeometryComponent::attribute_is_builtin(const blender::StringRef attribute_
 }
 
 blender::bke::ReadAttributeLookup GeometryComponent::attribute_try_get_for_read(
-    const StringRef attribute_name) const
+    const AttributeIDRef &attribute_id) const
 {
   using namespace blender::bke;
   const ComponentAttributeProviders *providers = this->get_attribute_providers();
   if (providers == nullptr) {
     return {};
   }
-  const BuiltinAttributeProvider *builtin_provider =
-      providers->builtin_attribute_providers().lookup_default_as(attribute_name, nullptr);
-  if (builtin_provider != nullptr) {
-    return {builtin_provider->try_get_for_read(*this), builtin_provider->domain()};
+  if (attribute_id.is_named()) {
+    const BuiltinAttributeProvider *builtin_provider =
+        providers->builtin_attribute_providers().lookup_default_as(attribute_id.name(), nullptr);
+    if (builtin_provider != nullptr) {
+      return {builtin_provider->try_get_for_read(*this), builtin_provider->domain()};
+    }
   }
   for (const DynamicAttributesProvider *dynamic_provider :
        providers->dynamic_attribute_providers()) {
-    ReadAttributeLookup attribute = dynamic_provider->try_get_for_read(*this, attribute_name);
+    ReadAttributeLookup attribute = dynamic_provider->try_get_for_read(*this, attribute_id);
     if (attribute) {
       return attribute;
     }
@@ -800,21 +852,23 @@ std::unique_ptr<blender::fn::GVArray> GeometryComponent::attribute_try_adapt_dom
 }
 
 blender::bke::WriteAttributeLookup GeometryComponent::attribute_try_get_for_write(
-    const StringRef attribute_name)
+    const AttributeIDRef &attribute_id)
 {
   using namespace blender::bke;
   const ComponentAttributeProviders *providers = this->get_attribute_providers();
   if (providers == nullptr) {
     return {};
   }
-  const BuiltinAttributeProvider *builtin_provider =
-      providers->builtin_attribute_providers().lookup_default_as(attribute_name, nullptr);
-  if (builtin_provider != nullptr) {
-    return {builtin_provider->try_get_for_write(*this), builtin_provider->domain()};
+  if (attribute_id.is_named()) {
+    const BuiltinAttributeProvider *builtin_provider =
+        providers->builtin_attribute_providers().lookup_default_as(attribute_id.name(), nullptr);
+    if (builtin_provider != nullptr) {
+      return {builtin_provider->try_get_for_write(*this), builtin_provider->domain()};
+    }
   }
   for (const DynamicAttributesProvider *dynamic_provider :
        providers->dynamic_attribute_providers()) {
-    WriteAttributeLookup attribute = dynamic_provider->try_get_for_write(*this, attribute_name);
+    WriteAttributeLookup attribute = dynamic_provider->try_get_for_write(*this, attribute_id);
     if (attribute) {
       return attribute;
     }
@@ -822,53 +876,57 @@ blender::bke::WriteAttributeLookup GeometryComponent::attribute_try_get_for_writ
   return {};
 }
 
-bool GeometryComponent::attribute_try_delete(const StringRef attribute_name)
+bool GeometryComponent::attribute_try_delete(const AttributeIDRef &attribute_id)
 {
   using namespace blender::bke;
   const ComponentAttributeProviders *providers = this->get_attribute_providers();
   if (providers == nullptr) {
     return {};
   }
-  const BuiltinAttributeProvider *builtin_provider =
-      providers->builtin_attribute_providers().lookup_default_as(attribute_name, nullptr);
-  if (builtin_provider != nullptr) {
-    return builtin_provider->try_delete(*this);
+  if (attribute_id.is_named()) {
+    const BuiltinAttributeProvider *builtin_provider =
+        providers->builtin_attribute_providers().lookup_default_as(attribute_id.name(), nullptr);
+    if (builtin_provider != nullptr) {
+      return builtin_provider->try_delete(*this);
+    }
   }
   bool success = false;
   for (const DynamicAttributesProvider *dynamic_provider :
        providers->dynamic_attribute_providers()) {
-    success = dynamic_provider->try_delete(*this, attribute_name) || success;
+    success = dynamic_provider->try_delete(*this, attribute_id) || success;
   }
   return success;
 }
 
-bool GeometryComponent::attribute_try_create(const StringRef attribute_name,
+bool GeometryComponent::attribute_try_create(const AttributeIDRef &attribute_id,
                                              const AttributeDomain domain,
                                              const CustomDataType data_type,
                                              const AttributeInit &initializer)
 {
   using namespace blender::bke;
-  if (attribute_name.is_empty()) {
+  if (!attribute_id) {
     return false;
   }
   const ComponentAttributeProviders *providers = this->get_attribute_providers();
   if (providers == nullptr) {
     return false;
   }
-  const BuiltinAttributeProvider *builtin_provider =
-      providers->builtin_attribute_providers().lookup_default_as(attribute_name, nullptr);
-  if (builtin_provider != nullptr) {
-    if (builtin_provider->domain() != domain) {
-      return false;
+  if (attribute_id.is_named()) {
+    const BuiltinAttributeProvider *builtin_provider =
+        providers->builtin_attribute_providers().lookup_default_as(attribute_id.name(), nullptr);
+    if (builtin_provider != nullptr) {
+      if (builtin_provider->domain() != domain) {
+        return false;
+      }
+      if (builtin_provider->data_type() != data_type) {
+        return false;
+      }
+      return builtin_provider->try_create(*this, initializer);
     }
-    if (builtin_provider->data_type() != data_type) {
-      return false;
-    }
-    return builtin_provider->try_create(*this, initializer);
   }
   for (const DynamicAttributesProvider *dynamic_provider :
        providers->dynamic_attribute_providers()) {
-    if (dynamic_provider->try_create(*this, attribute_name, domain, data_type, initializer)) {
+    if (dynamic_provider->try_create(*this, attribute_id, domain, data_type, initializer)) {
       return true;
     }
   }
@@ -894,13 +952,14 @@ bool GeometryComponent::attribute_try_create_builtin(const blender::StringRef at
   return builtin_provider->try_create(*this, initializer);
 }
 
-Set<std::string> GeometryComponent::attribute_names() const
+Set<AttributeIDRef> GeometryComponent::attribute_ids() const
 {
-  Set<std::string> attributes;
-  this->attribute_foreach([&](StringRefNull name, const AttributeMetaData &UNUSED(meta_data)) {
-    attributes.add(name);
-    return true;
-  });
+  Set<AttributeIDRef> attributes;
+  this->attribute_foreach(
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &UNUSED(meta_data)) {
+        attributes.add(attribute_id);
+        return true;
+      });
   return attributes;
 }
 
@@ -931,9 +990,9 @@ bool GeometryComponent::attribute_foreach(const AttributeForeachCallback callbac
   }
   for (const DynamicAttributesProvider *provider : providers->dynamic_attribute_providers()) {
     const bool continue_loop = provider->foreach_attribute(
-        *this, [&](StringRefNull name, const AttributeMetaData &meta_data) {
-          if (handled_attribute_names.add(name)) {
-            return callback(name, meta_data);
+        *this, [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+          if (attribute_id.is_anonymous() || handled_attribute_names.add(attribute_id.name())) {
+            return callback(attribute_id, meta_data);
           }
           return true;
         });
@@ -945,9 +1004,9 @@ bool GeometryComponent::attribute_foreach(const AttributeForeachCallback callbac
   return true;
 }
 
-bool GeometryComponent::attribute_exists(const blender::StringRef attribute_name) const
+bool GeometryComponent::attribute_exists(const AttributeIDRef &attribute_id) const
 {
-  blender::bke::ReadAttributeLookup attribute = this->attribute_try_get_for_read(attribute_name);
+  blender::bke::ReadAttributeLookup attribute = this->attribute_try_get_for_read(attribute_id);
   if (attribute) {
     return true;
   }
@@ -955,16 +1014,17 @@ bool GeometryComponent::attribute_exists(const blender::StringRef attribute_name
 }
 
 std::optional<AttributeMetaData> GeometryComponent::attribute_get_meta_data(
-    const StringRef attribute_name) const
+    const AttributeIDRef &attribute_id) const
 {
   std::optional<AttributeMetaData> result{std::nullopt};
-  this->attribute_foreach([&](StringRefNull name, const AttributeMetaData &meta_data) {
-    if (attribute_name == name) {
-      result = meta_data;
-      return false;
-    }
-    return true;
-  });
+  this->attribute_foreach(
+      [&](const AttributeIDRef &current_attribute_id, const AttributeMetaData &meta_data) {
+        if (attribute_id == current_attribute_id) {
+          result = meta_data;
+          return false;
+        }
+        return true;
+      });
   return result;
 }
 
@@ -977,11 +1037,11 @@ static std::unique_ptr<blender::fn::GVArray> try_adapt_data_type(
 }
 
 std::unique_ptr<blender::fn::GVArray> GeometryComponent::attribute_try_get_for_read(
-    const StringRef attribute_name,
+    const AttributeIDRef &attribute_id,
     const AttributeDomain domain,
     const CustomDataType data_type) const
 {
-  blender::bke::ReadAttributeLookup attribute = this->attribute_try_get_for_read(attribute_name);
+  blender::bke::ReadAttributeLookup attribute = this->attribute_try_get_for_read(attribute_id);
   if (!attribute) {
     return {};
   }
@@ -1007,13 +1067,13 @@ std::unique_ptr<blender::fn::GVArray> GeometryComponent::attribute_try_get_for_r
 }
 
 std::unique_ptr<blender::bke::GVArray> GeometryComponent::attribute_try_get_for_read(
-    const StringRef attribute_name, const AttributeDomain domain) const
+    const AttributeIDRef &attribute_id, const AttributeDomain domain) const
 {
   if (!this->attribute_domain_supported(domain)) {
     return {};
   }
 
-  blender::bke::ReadAttributeLookup attribute = this->attribute_try_get_for_read(attribute_name);
+  blender::bke::ReadAttributeLookup attribute = this->attribute_try_get_for_read(attribute_id);
   if (!attribute) {
     return {};
   }
@@ -1026,9 +1086,9 @@ std::unique_ptr<blender::bke::GVArray> GeometryComponent::attribute_try_get_for_
 }
 
 blender::bke::ReadAttributeLookup GeometryComponent::attribute_try_get_for_read(
-    const blender::StringRef attribute_name, const CustomDataType data_type) const
+    const AttributeIDRef &attribute_id, const CustomDataType data_type) const
 {
-  blender::bke::ReadAttributeLookup attribute = this->attribute_try_get_for_read(attribute_name);
+  blender::bke::ReadAttributeLookup attribute = this->attribute_try_get_for_read(attribute_id);
   if (!attribute) {
     return {};
   }
@@ -1043,13 +1103,13 @@ blender::bke::ReadAttributeLookup GeometryComponent::attribute_try_get_for_read(
 }
 
 std::unique_ptr<blender::bke::GVArray> GeometryComponent::attribute_get_for_read(
-    const StringRef attribute_name,
+    const AttributeIDRef &attribute_id,
     const AttributeDomain domain,
     const CustomDataType data_type,
     const void *default_value) const
 {
   std::unique_ptr<blender::bke::GVArray> varray = this->attribute_try_get_for_read(
-      attribute_name, domain, data_type);
+      attribute_id, domain, data_type);
   if (varray) {
     return varray;
   }
@@ -1065,15 +1125,22 @@ class GVMutableAttribute_For_OutputAttribute
     : public blender::fn::GVMutableArray_For_GMutableSpan {
  public:
   GeometryComponent *component;
-  std::string final_name;
+  std::string attribute_name;
+  blender::bke::WeakAnonymousAttributeID anonymous_attribute_id;
 
   GVMutableAttribute_For_OutputAttribute(GMutableSpan data,
                                          GeometryComponent &component,
-                                         std::string final_name)
-      : blender::fn::GVMutableArray_For_GMutableSpan(data),
-        component(&component),
-        final_name(std::move(final_name))
+                                         const AttributeIDRef &attribute_id)
+      : blender::fn::GVMutableArray_For_GMutableSpan(data), component(&component)
   {
+    if (attribute_id.is_named()) {
+      this->attribute_name = attribute_id.name();
+    }
+    else {
+      const AnonymousAttributeID *anonymous_id = &attribute_id.anonymous_id();
+      BKE_anonymous_attribute_id_increment_weak(anonymous_id);
+      this->anonymous_attribute_id = blender::bke::WeakAnonymousAttributeID{anonymous_id};
+    }
   }
 
   ~GVMutableAttribute_For_OutputAttribute() override
@@ -1083,7 +1150,7 @@ class GVMutableAttribute_For_OutputAttribute
   }
 };
 
-static void save_output_attribute(blender::bke::OutputAttribute &output_attribute)
+static void save_output_attribute(OutputAttribute &output_attribute)
 {
   using namespace blender;
   using namespace blender::fn;
@@ -1093,21 +1160,28 @@ static void save_output_attribute(blender::bke::OutputAttribute &output_attribut
       dynamic_cast<GVMutableAttribute_For_OutputAttribute &>(output_attribute.varray());
 
   GeometryComponent &component = *varray.component;
-  const StringRefNull name = varray.final_name;
+  AttributeIDRef attribute_id;
+  if (!varray.attribute_name.empty()) {
+    attribute_id = varray.attribute_name;
+  }
+  else {
+    attribute_id = varray.anonymous_attribute_id.extract();
+  }
   const AttributeDomain domain = output_attribute.domain();
   const CustomDataType data_type = output_attribute.custom_data_type();
   const CPPType &cpp_type = output_attribute.cpp_type();
 
-  component.attribute_try_delete(name);
-  if (!component.attribute_try_create(
-          varray.final_name, domain, data_type, AttributeInitDefault())) {
-    CLOG_WARN(&LOG,
-              "Could not create the '%s' attribute with type '%s'.",
-              name.c_str(),
-              cpp_type.name().c_str());
+  component.attribute_try_delete(attribute_id);
+  if (!component.attribute_try_create(attribute_id, domain, data_type, AttributeInitDefault())) {
+    if (!varray.attribute_name.empty()) {
+      CLOG_WARN(&LOG,
+                "Could not create the '%s' attribute with type '%s'.",
+                varray.attribute_name.c_str(),
+                cpp_type.name().c_str());
+    }
     return;
   }
-  WriteAttributeLookup write_attribute = component.attribute_try_get_for_write(name);
+  WriteAttributeLookup write_attribute = component.attribute_try_get_for_write(attribute_id);
   BUFFER_FOR_CPP_TYPE_VALUE(varray.type(), buffer);
   for (const int i : IndexRange(varray.size())) {
     varray.get(i, buffer);
@@ -1115,19 +1189,18 @@ static void save_output_attribute(blender::bke::OutputAttribute &output_attribut
   }
 }
 
-static blender::bke::OutputAttribute create_output_attribute(
-    GeometryComponent &component,
-    const blender::StringRef attribute_name,
-    const AttributeDomain domain,
-    const CustomDataType data_type,
-    const bool ignore_old_values,
-    const void *default_value)
+static OutputAttribute create_output_attribute(GeometryComponent &component,
+                                               const AttributeIDRef &attribute_id,
+                                               const AttributeDomain domain,
+                                               const CustomDataType data_type,
+                                               const bool ignore_old_values,
+                                               const void *default_value)
 {
   using namespace blender;
   using namespace blender::fn;
   using namespace blender::bke;
 
-  if (attribute_name.is_empty()) {
+  if (!attribute_id) {
     return {};
   }
 
@@ -1135,7 +1208,8 @@ static blender::bke::OutputAttribute create_output_attribute(
   BLI_assert(cpp_type != nullptr);
   const nodes::DataTypeConversions &conversions = nodes::get_implicit_type_conversions();
 
-  if (component.attribute_is_builtin(attribute_name)) {
+  if (attribute_id.is_named() && component.attribute_is_builtin(attribute_id.name())) {
+    const StringRef attribute_name = attribute_id.name();
     WriteAttributeLookup attribute = component.attribute_try_get_for_write(attribute_name);
     if (!attribute) {
       if (default_value) {
@@ -1169,18 +1243,18 @@ static blender::bke::OutputAttribute create_output_attribute(
 
   const int domain_size = component.attribute_domain_size(domain);
 
-  WriteAttributeLookup attribute = component.attribute_try_get_for_write(attribute_name);
+  WriteAttributeLookup attribute = component.attribute_try_get_for_write(attribute_id);
   if (!attribute) {
     if (default_value) {
       const GVArray_For_SingleValueRef default_varray{*cpp_type, domain_size, default_value};
       component.attribute_try_create(
-          attribute_name, domain, data_type, AttributeInitVArray(&default_varray));
+          attribute_id, domain, data_type, AttributeInitVArray(&default_varray));
     }
     else {
-      component.attribute_try_create(attribute_name, domain, data_type, AttributeInitDefault());
+      component.attribute_try_create(attribute_id, domain, data_type, AttributeInitDefault());
     }
 
-    attribute = component.attribute_try_get_for_write(attribute_name);
+    attribute = component.attribute_try_get_for_write(attribute_id);
     if (!attribute) {
       /* Can't create the attribute. */
       return {};
@@ -1202,28 +1276,88 @@ static blender::bke::OutputAttribute create_output_attribute(
   else {
     /* Fill the temporary array with values from the existing attribute. */
     GVArrayPtr old_varray = component.attribute_get_for_read(
-        attribute_name, domain, data_type, default_value);
+        attribute_id, domain, data_type, default_value);
     old_varray->materialize_to_uninitialized(IndexRange(domain_size), data);
   }
   GVMutableArrayPtr varray = std::make_unique<GVMutableAttribute_For_OutputAttribute>(
-      GMutableSpan{*cpp_type, data, domain_size}, component, attribute_name);
+      GMutableSpan{*cpp_type, data, domain_size}, component, attribute_id);
 
   return OutputAttribute(std::move(varray), domain, save_output_attribute, true);
 }
 
-blender::bke::OutputAttribute GeometryComponent::attribute_try_get_for_output(
-    const StringRef attribute_name,
-    const AttributeDomain domain,
-    const CustomDataType data_type,
-    const void *default_value)
+OutputAttribute GeometryComponent::attribute_try_get_for_output(const AttributeIDRef &attribute_id,
+                                                                const AttributeDomain domain,
+                                                                const CustomDataType data_type,
+                                                                const void *default_value)
 {
-  return create_output_attribute(*this, attribute_name, domain, data_type, false, default_value);
+  return create_output_attribute(*this, attribute_id, domain, data_type, false, default_value);
 }
 
-blender::bke::OutputAttribute GeometryComponent::attribute_try_get_for_output_only(
-    const blender::StringRef attribute_name,
+OutputAttribute GeometryComponent::attribute_try_get_for_output_only(
+    const AttributeIDRef &attribute_id,
     const AttributeDomain domain,
     const CustomDataType data_type)
 {
-  return create_output_attribute(*this, attribute_name, domain, data_type, true, nullptr);
+  return create_output_attribute(*this, attribute_id, domain, data_type, true, nullptr);
 }
+
+namespace blender::bke {
+
+const GVArray *AttributeFieldInput::get_varray_for_context(const fn::FieldContext &context,
+                                                           IndexMask UNUSED(mask),
+                                                           ResourceScope &scope) const
+{
+  if (const GeometryComponentFieldContext *geometry_context =
+          dynamic_cast<const GeometryComponentFieldContext *>(&context)) {
+    const GeometryComponent &component = geometry_context->geometry_component();
+    const AttributeDomain domain = geometry_context->domain();
+    const CustomDataType data_type = cpp_type_to_custom_data_type(*type_);
+    GVArrayPtr attribute = component.attribute_try_get_for_read(name_, domain, data_type);
+    return scope.add(std::move(attribute), __func__);
+  }
+  return nullptr;
+}
+
+uint64_t AttributeFieldInput::hash() const
+{
+  return get_default_hash_2(name_, type_);
+}
+
+bool AttributeFieldInput::is_equal_to(const fn::FieldNode &other) const
+{
+  if (const AttributeFieldInput *other_typed = dynamic_cast<const AttributeFieldInput *>(&other)) {
+    return name_ == other_typed->name_ && type_ == other_typed->type_;
+  }
+  return false;
+}
+
+const GVArray *AnonymousAttributeFieldInput::get_varray_for_context(
+    const fn::FieldContext &context, IndexMask UNUSED(mask), ResourceScope &scope) const
+{
+  if (const GeometryComponentFieldContext *geometry_context =
+          dynamic_cast<const GeometryComponentFieldContext *>(&context)) {
+    const GeometryComponent &component = geometry_context->geometry_component();
+    const AttributeDomain domain = geometry_context->domain();
+    const CustomDataType data_type = cpp_type_to_custom_data_type(*type_);
+    GVArrayPtr attribute = component.attribute_try_get_for_read(
+        anonymous_id_.get(), domain, data_type);
+    return scope.add(std::move(attribute), __func__);
+  }
+  return nullptr;
+}
+
+uint64_t AnonymousAttributeFieldInput::hash() const
+{
+  return get_default_hash_2(anonymous_id_.get(), type_);
+}
+
+bool AnonymousAttributeFieldInput::is_equal_to(const fn::FieldNode &other) const
+{
+  if (const AnonymousAttributeFieldInput *other_typed =
+          dynamic_cast<const AnonymousAttributeFieldInput *>(&other)) {
+    return anonymous_id_.get() == other_typed->anonymous_id_.get() && type_ == other_typed->type_;
+  }
+  return false;
+}
+
+}  // namespace blender::bke

source/blender/blenkernel/intern/attribute_access_intern.hh

@@ -116,12 +116,13 @@ class BuiltinAttributeProvider {
 class DynamicAttributesProvider {
  public:
   virtual ReadAttributeLookup try_get_for_read(const GeometryComponent &component,
-                                               const StringRef attribute_name) const = 0;
+                                               const AttributeIDRef &attribute_id) const = 0;
   virtual WriteAttributeLookup try_get_for_write(GeometryComponent &component,
-                                                 const StringRef attribute_name) const = 0;
-  virtual bool try_delete(GeometryComponent &component, const StringRef attribute_name) const = 0;
+                                                 const AttributeIDRef &attribute_id) const = 0;
+  virtual bool try_delete(GeometryComponent &component,
+                          const AttributeIDRef &attribute_id) const = 0;
   virtual bool try_create(GeometryComponent &UNUSED(component),
-                          const StringRef UNUSED(attribute_name),
+                          const AttributeIDRef &UNUSED(attribute_id),
                           const AttributeDomain UNUSED(domain),
                           const CustomDataType UNUSED(data_type),
                           const AttributeInit &UNUSED(initializer)) const
@@ -154,15 +155,15 @@ class CustomDataAttributeProvider final : public DynamicAttributesProvider {
   }
 
   ReadAttributeLookup try_get_for_read(const GeometryComponent &component,
-                                       const StringRef attribute_name) const final;
+                                       const AttributeIDRef &attribute_id) const final;
 
   WriteAttributeLookup try_get_for_write(GeometryComponent &component,
-                                         const StringRef attribute_name) const final;
+                                         const AttributeIDRef &attribute_id) const final;
 
-  bool try_delete(GeometryComponent &component, const StringRef attribute_name) const final;
+  bool try_delete(GeometryComponent &component, const AttributeIDRef &attribute_id) const final;
 
   bool try_create(GeometryComponent &component,
-                  const StringRef attribute_name,
+                  const AttributeIDRef &attribute_id,
                   const AttributeDomain domain,
                   const CustomDataType data_type,
                   const AttributeInit &initializer) const final;
@@ -231,10 +232,10 @@ class NamedLegacyCustomDataProvider final : public DynamicAttributesProvider {
   }
 
   ReadAttributeLookup try_get_for_read(const GeometryComponent &component,
-                                       const StringRef attribute_name) const final;
+                                       const AttributeIDRef &attribute_id) const final;
   WriteAttributeLookup try_get_for_write(GeometryComponent &component,
-                                         const StringRef attribute_name) const final;
-  bool try_delete(GeometryComponent &component, const StringRef attribute_name) const final;
+                                         const AttributeIDRef &attribute_id) const final;
+  bool try_delete(GeometryComponent &component, const AttributeIDRef &attribute_id) const final;
   bool foreach_attribute(const GeometryComponent &component,
                          const AttributeForeachCallback callback) const final;
   void foreach_domain(const FunctionRef<void(AttributeDomain)> callback) const final;

source/blender/blenkernel/intern/curve_eval.cc

@@ -25,6 +25,7 @@
 
 #include "DNA_curve_types.h"
 
+#include "BKE_anonymous_attribute.hh"
 #include "BKE_curve.h"
 #include "BKE_spline.hh"
 
@@ -37,6 +38,7 @@ using blender::MutableSpan;
 using blender::Span;
 using blender::StringRefNull;
 using blender::Vector;
+using blender::bke::AttributeIDRef;
 
 blender::Span<SplinePtr> CurveEval::splines() const
 {
@@ -330,13 +332,13 @@ void CurveEval::assert_valid_point_attributes() const
     return;
   }
   const int layer_len = splines_.first()->attributes.data.totlayer;
-  Map<StringRefNull, AttributeMetaData> map;
+  Map<AttributeIDRef, AttributeMetaData> map;
   for (const SplinePtr &spline : splines_) {
     BLI_assert(spline->attributes.data.totlayer == layer_len);
     spline->attributes.foreach_attribute(
-        [&](StringRefNull name, const AttributeMetaData &meta_data) {
+        [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
           map.add_or_modify(
-              name,
+              attribute_id,
               [&](AttributeMetaData *map_data) {
                 /* All unique attribute names should be added on the first spline. */
                 BLI_assert(spline == splines_.first());

source/blender/blenkernel/intern/customdata.c

@@ -46,6 +46,7 @@
 
 #include "BLT_translation.h"
 
+#include "BKE_anonymous_attribute.h"
 #include "BKE_customdata.h"
 #include "BKE_customdata_file.h"
 #include "BKE_deform.h"
@@ -2127,6 +2128,11 @@ bool CustomData_merge(const struct CustomData *source,
     if (flag & CD_FLAG_NOCOPY) {
       continue;
     }
+    if (layer->anonymous_id &&
+        !BKE_anonymous_attribute_id_has_strong_references(layer->anonymous_id)) {
+      /* This attribute is not referenced anymore, so it can be treated as if it didn't exist. */
+      continue;
+    }
     if (!(mask & CD_TYPE_AS_MASK(type))) {
       continue;
     }
@@ -2166,6 +2172,11 @@ bool CustomData_merge(const struct CustomData *source,
       newlayer->active_mask = lastmask;
       newlayer->flag |= flag & (CD_FLAG_EXTERNAL | CD_FLAG_IN_MEMORY);
       changed = true;
+
+      if (layer->anonymous_id != NULL) {
+        BKE_anonymous_attribute_id_increment_weak(layer->anonymous_id);
+        newlayer->anonymous_id = layer->anonymous_id;
+      }
     }
   }
 
@@ -2206,6 +2217,10 @@ static void customData_free_layer__internal(CustomDataLayer *layer, int totelem)
 {
   const LayerTypeInfo *typeInfo;
 
+  if (layer->anonymous_id != NULL) {
+    BKE_anonymous_attribute_id_decrement_weak(layer->anonymous_id);
+    layer->anonymous_id = NULL;
+  }
   if (!(layer->flag & CD_FLAG_NOFREE) && layer->data) {
     typeInfo = layerType_getInfo(layer->type);
 
@@ -2649,6 +2664,27 @@ void *CustomData_add_layer_named(CustomData *data,
   return NULL;
 }
 
+void *CustomData_add_layer_anonymous(struct CustomData *data,
+                                     int type,
+                                     eCDAllocType alloctype,
+                                     void *layerdata,
+                                     int totelem,
+                                     const AnonymousAttributeID *anonymous_id)
+{
+  const char *name = BKE_anonymous_attribute_id_internal_name(anonymous_id);
+  CustomDataLayer *layer = customData_add_layer__internal(
+      data, type, alloctype, layerdata, totelem, name);
+  CustomData_update_typemap(data);
+
+  if (layer == NULL) {
+    return NULL;
+  }
+
+  BKE_anonymous_attribute_id_increment_weak(anonymous_id);
+  layer->anonymous_id = anonymous_id;
+  return layer->data;
+}
+
 bool CustomData_free_layer(CustomData *data, int type, int totelem, int index)
 {
   const int index_first = CustomData_get_layer_index(data, type);
@@ -2812,6 +2848,20 @@ void *CustomData_duplicate_referenced_layer_named(CustomData *data,
   return customData_duplicate_referenced_layer_index(data, layer_index, totelem);
 }
 
+void *CustomData_duplicate_referenced_layer_anonymous(CustomData *data,
+                                                      const int UNUSED(type),
+                                                      const AnonymousAttributeID *anonymous_id,
+                                                      const int totelem)
+{
+  for (int i = 0; i < data->totlayer; i++) {
+    if (data->layers[i].anonymous_id == anonymous_id) {
+      return customData_duplicate_referenced_layer_index(data, i, totelem);
+    }
+  }
+  BLI_assert_unreachable();
+  return NULL;
+}
+
 void CustomData_duplicate_referenced_layers(CustomData *data, int totelem)
 {
   for (int i = 0; i < data->totlayer; i++) {
@@ -4244,7 +4294,8 @@ void CustomData_blend_write_prepare(CustomData *data,
 
   for (i = 0, j = 0; i < totlayer; i++) {
     CustomDataLayer *layer = &data->layers[i];
-    if (layer->flag & CD_FLAG_NOCOPY) { /* Layers with this flag set are not written to file. */
+    /* Layers with this flag set are not written to file. */
+    if ((layer->flag & CD_FLAG_NOCOPY) || layer->anonymous_id != NULL) {
       data->totlayer--;
       // CLOG_WARN(&LOG, "skipping layer %p (%s)", layer, layer->name);
     }

source/blender/blenkernel/intern/geometry_component_curve.cc

@@ -892,7 +892,7 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
 
  public:
   ReadAttributeLookup try_get_for_read(const GeometryComponent &component,
-                                       const StringRef attribute_name) const final
+                                       const AttributeIDRef &attribute_id) const final
   {
     const CurveEval *curve = get_curve_from_component_for_read(component);
     if (curve == nullptr || curve->splines().size() == 0) {
@@ -902,13 +902,13 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
     Span<SplinePtr> splines = curve->splines();
     Vector<GSpan> spans; /* GSpan has no default constructor. */
     spans.reserve(splines.size());
-    std::optional<GSpan> first_span = splines[0]->attributes.get_for_read(attribute_name);
+    std::optional<GSpan> first_span = splines[0]->attributes.get_for_read(attribute_id);
     if (!first_span) {
       return {};
     }
     spans.append(*first_span);
     for (const int i : IndexRange(1, splines.size() - 1)) {
-      std::optional<GSpan> span = splines[i]->attributes.get_for_read(attribute_name);
+      std::optional<GSpan> span = splines[i]->attributes.get_for_read(attribute_id);
       if (!span) {
         /* All splines should have the same set of data layers. It would be possible to recover
          * here and return partial data instead, but that would add a lot of complexity for a
@@ -945,7 +945,7 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
 
   /* This function is almost the same as #try_get_for_read, but without const. */
   WriteAttributeLookup try_get_for_write(GeometryComponent &component,
-                                         const StringRef attribute_name) const final
+                                         const AttributeIDRef &attribute_id) const final
   {
     CurveEval *curve = get_curve_from_component_for_write(component);
     if (curve == nullptr || curve->splines().size() == 0) {
@@ -955,13 +955,13 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
     MutableSpan<SplinePtr> splines = curve->splines();
     Vector<GMutableSpan> spans; /* GMutableSpan has no default constructor. */
     spans.reserve(splines.size());
-    std::optional<GMutableSpan> first_span = splines[0]->attributes.get_for_write(attribute_name);
+    std::optional<GMutableSpan> first_span = splines[0]->attributes.get_for_write(attribute_id);
     if (!first_span) {
       return {};
     }
     spans.append(*first_span);
     for (const int i : IndexRange(1, splines.size() - 1)) {
-      std::optional<GMutableSpan> span = splines[i]->attributes.get_for_write(attribute_name);
+      std::optional<GMutableSpan> span = splines[i]->attributes.get_for_write(attribute_id);
       if (!span) {
         /* All splines should have the same set of data layers. It would be possible to recover
          * here and return partial data instead, but that would add a lot of complexity for a
@@ -996,7 +996,7 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
     return attribute;
   }
 
-  bool try_delete(GeometryComponent &component, const StringRef attribute_name) const final
+  bool try_delete(GeometryComponent &component, const AttributeIDRef &attribute_id) const final
   {
     CurveEval *curve = get_curve_from_component_for_write(component);
     if (curve == nullptr) {
@@ -1006,7 +1006,7 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
     /* Reuse the boolean for all splines; we expect all splines to have the same attributes. */
     bool layer_freed = false;
     for (SplinePtr &spline : curve->splines()) {
-      layer_freed = spline->attributes.remove(attribute_name);
+      layer_freed = spline->attributes.remove(attribute_id);
     }
     return layer_freed;
   }
@@ -1034,7 +1034,7 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
   }
 
   bool try_create(GeometryComponent &component,
-                  const StringRef attribute_name,
+                  const AttributeIDRef &attribute_id,
                   const AttributeDomain domain,
                   const CustomDataType data_type,
                   const AttributeInit &initializer) const final
@@ -1053,7 +1053,7 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
     /* First check the one case that allows us to avoid copying the input data. */
     if (splines.size() == 1 && initializer.type == AttributeInit::Type::MoveArray) {
       void *source_data = static_cast<const AttributeInitMove &>(initializer).data;
-      if (!splines[0]->attributes.create_by_move(attribute_name, data_type, source_data)) {
+      if (!splines[0]->attributes.create_by_move(attribute_id, data_type, source_data)) {
         MEM_freeN(source_data);
         return false;
       }
@@ -1062,7 +1062,7 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
 
     /* Otherwise just create a custom data layer on each of the splines. */
     for (const int i : splines.index_range()) {
-      if (!splines[i]->attributes.create(attribute_name, data_type)) {
+      if (!splines[i]->attributes.create(attribute_id, data_type)) {
         /* If attribute creation fails on one of the splines, we cannot leave the custom data
          * layers in the previous splines around, so delete them before returning. However,
          * this is not an expected case. */
@@ -1076,7 +1076,7 @@ class DynamicPointAttributeProvider final : public DynamicAttributesProvider {
       return true;
     }
 
-    WriteAttributeLookup write_attribute = this->try_get_for_write(component, attribute_name);
+    WriteAttributeLookup write_attribute = this->try_get_for_write(component, attribute_id);
     /* We just created the attribute, it should exist. */
     BLI_assert(write_attribute);
 

source/blender/blenkernel/intern/geometry_component_mesh.cc

@@ -818,16 +818,20 @@ class VArray_For_VertexWeights final : public VArray<float> {
 class VertexGroupsAttributeProvider final : public DynamicAttributesProvider {
  public:
   ReadAttributeLookup try_get_for_read(const GeometryComponent &component,
-                                       const StringRef attribute_name) const final
+                                       const AttributeIDRef &attribute_id) const final
   {
     BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
+    if (!attribute_id.is_named()) {
+      return {};
+    }
     const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
     const Mesh *mesh = mesh_component.get_for_read();
     if (mesh == nullptr) {
       return {};
     }
+    const std::string name = attribute_id.name();
     const int vertex_group_index = BLI_findstringindex(
-        &mesh->vertex_group_names, attribute_name.data(), offsetof(bDeformGroup, name));
+        &mesh->vertex_group_names, name.c_str(), offsetof(bDeformGroup, name));
     if (vertex_group_index < 0) {
       return {};
     }
@@ -843,17 +847,21 @@ class VertexGroupsAttributeProvider final : public DynamicAttributesProvider {
   }
 
   WriteAttributeLookup try_get_for_write(GeometryComponent &component,
-                                         const StringRef attribute_name) const final
+                                         const AttributeIDRef &attribute_id) const final
   {
     BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
+    if (!attribute_id.is_named()) {
+      return {};
+    }
     MeshComponent &mesh_component = static_cast<MeshComponent &>(component);
     Mesh *mesh = mesh_component.get_for_write();
     if (mesh == nullptr) {
       return {};
     }
 
+    const std::string name = attribute_id.name();
     const int vertex_group_index = BLI_findstringindex(
-        &mesh->vertex_group_names, attribute_name.data(), offsetof(bDeformGroup, name));
+        &mesh->vertex_group_names, name.c_str(), offsetof(bDeformGroup, name));
     if (vertex_group_index < 0) {
       return {};
     }
@@ -872,17 +880,21 @@ class VertexGroupsAttributeProvider final : public DynamicAttributesProvider {
         ATTR_DOMAIN_POINT};
   }
 
-  bool try_delete(GeometryComponent &component, const StringRef attribute_name) const final
+  bool try_delete(GeometryComponent &component, const AttributeIDRef &attribute_id) const final
   {
     BLI_assert(component.type() == GEO_COMPONENT_TYPE_MESH);
+    if (!attribute_id.is_named()) {
+      return false;
+    }
     MeshComponent &mesh_component = static_cast<MeshComponent &>(component);
     Mesh *mesh = mesh_component.get_for_write();
     if (mesh == nullptr) {
       return true;
     }
 
+    const std::string name = attribute_id.name();
     const int vertex_group_index = BLI_findstringindex(
-        &mesh->vertex_group_names, attribute_name.data(), offsetof(bDeformGroup, name));
+        &mesh->vertex_group_names, name.c_str(), offsetof(bDeformGroup, name));
     if (vertex_group_index < 0) {
       return false;
     }

source/blender/blenkernel/intern/geometry_set_instances.cc

@@ -331,7 +331,7 @@ void geometry_set_instances_attribute_foreach(const GeometrySet &geometry_set,
 void geometry_set_gather_instances_attribute_info(Span<GeometryInstanceGroup> set_groups,
                                                   Span<GeometryComponentType> component_types,
                                                   const Set<std::string> &ignored_attributes,
-                                                  Map<std::string, AttributeKind> &r_attributes)
+                                                  Map<AttributeIDRef, AttributeKind> &r_attributes)
 {
   for (const GeometryInstanceGroup &set_group : set_groups) {
     const GeometrySet &set = set_group.geometry_set;
@@ -341,23 +341,24 @@ void geometry_set_gather_instances_attribute_info(Span<GeometryInstanceGroup> se
       }
       const GeometryComponent &component = *set.get_component_for_read(component_type);
 
-      component.attribute_foreach([&](StringRefNull name, const AttributeMetaData &meta_data) {
-        if (ignored_attributes.contains(name)) {
-          return true;
-        }
-        auto add_info = [&](AttributeKind *attribute_kind) {
-          attribute_kind->domain = meta_data.domain;
-          attribute_kind->data_type = meta_data.data_type;
-        };
-        auto modify_info = [&](AttributeKind *attribute_kind) {
-          attribute_kind->domain = meta_data.domain; /* TODO: Use highest priority domain. */
-          attribute_kind->data_type = bke::attribute_data_type_highest_complexity(
-              {attribute_kind->data_type, meta_data.data_type});
-        };
+      component.attribute_foreach(
+          [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+            if (attribute_id.is_named() && ignored_attributes.contains(attribute_id.name())) {
+              return true;
+            }
+            auto add_info = [&](AttributeKind *attribute_kind) {
+              attribute_kind->domain = meta_data.domain;
+              attribute_kind->data_type = meta_data.data_type;
+            };
+            auto modify_info = [&](AttributeKind *attribute_kind) {
+              attribute_kind->domain = meta_data.domain; /* TODO: Use highest priority domain. */
+              attribute_kind->data_type = bke::attribute_data_type_highest_complexity(
+                  {attribute_kind->data_type, meta_data.data_type});
+            };
 
-        r_attributes.add_or_modify(name, add_info, modify_info);
-        return true;
-      });
+            r_attributes.add_or_modify(attribute_id, add_info, modify_info);
+            return true;
+          });
     }
   }
 }
@@ -512,11 +513,11 @@ static Mesh *join_mesh_topology_and_builtin_attributes(Span<GeometryInstanceGrou
 
 static void join_attributes(Span<GeometryInstanceGroup> set_groups,
                             Span<GeometryComponentType> component_types,
-                            const Map<std::string, AttributeKind> &attribute_info,
+                            const Map<AttributeIDRef, AttributeKind> &attribute_info,
                             GeometryComponent &result)
 {
-  for (Map<std::string, AttributeKind>::Item entry : attribute_info.items()) {
-    StringRef name = entry.key;
+  for (Map<AttributeIDRef, AttributeKind>::Item entry : attribute_info.items()) {
+    const AttributeIDRef attribute_id = entry.key;
     const AttributeDomain domain_output = entry.value.domain;
     const CustomDataType data_type_output = entry.value.data_type;
     const CPPType *cpp_type = bke::custom_data_type_to_cpp_type(data_type_output);
@@ -524,7 +525,7 @@ static void join_attributes(Span<GeometryInstanceGroup> set_groups,
 
     result.attribute_try_create(
         entry.key, domain_output, data_type_output, AttributeInitDefault());
-    WriteAttributeLookup write_attribute = result.attribute_try_get_for_write(name);
+    WriteAttributeLookup write_attribute = result.attribute_try_get_for_write(attribute_id);
     if (!write_attribute || &write_attribute.varray->type() != cpp_type ||
         write_attribute.domain != domain_output) {
       continue;
@@ -543,7 +544,7 @@ static void join_attributes(Span<GeometryInstanceGroup> set_groups,
             continue; /* Domain size is 0, so no need to increment the offset. */
           }
           GVArrayPtr source_attribute = component.attribute_try_get_for_read(
-              name, domain_output, data_type_output);
+              attribute_id, domain_output, data_type_output);
 
           if (source_attribute) {
             fn::GVArray_GSpan src_span{*source_attribute};
@@ -653,7 +654,7 @@ static void join_instance_groups_mesh(Span<GeometryInstanceGroup> set_groups,
   }
 
   /* Don't copy attributes that are stored directly in the mesh data structs. */
-  Map<std::string, AttributeKind> attributes;
+  Map<AttributeIDRef, AttributeKind> attributes;
   geometry_set_gather_instances_attribute_info(
       set_groups,
       component_types,
@@ -674,7 +675,7 @@ static void join_instance_groups_pointcloud(Span<GeometryInstanceGroup> set_grou
   PointCloudComponent &dst_component = result.get_component_for_write<PointCloudComponent>();
   dst_component.replace(new_pointcloud);
 
-  Map<std::string, AttributeKind> attributes;
+  Map<AttributeIDRef, AttributeKind> attributes;
   geometry_set_gather_instances_attribute_info(
       set_groups, {GEO_COMPONENT_TYPE_POINT_CLOUD}, {"position"}, attributes);
   join_attributes(set_groups,
@@ -708,7 +709,7 @@ static void join_instance_groups_curve(Span<GeometryInstanceGroup> set_groups, G
   CurveComponent &dst_component = result.get_component_for_write<CurveComponent>();
   dst_component.replace(curve);
 
-  Map<std::string, AttributeKind> attributes;
+  Map<AttributeIDRef, AttributeKind> attributes;
   geometry_set_gather_instances_attribute_info(
       set_groups,
       {GEO_COMPONENT_TYPE_CURVE},

source/blender/blenkernel/intern/node.cc

@@ -5140,6 +5140,7 @@ static void registerGeometryNodes()
   register_node_type_geo_attribute_convert();
   register_node_type_geo_attribute_curve_map();
   register_node_type_geo_attribute_fill();
+  register_node_type_geo_attribute_capture();
   register_node_type_geo_attribute_map_range();
   register_node_type_geo_attribute_math();
   register_node_type_geo_attribute_mix();
@@ -5174,7 +5175,10 @@ static void registerGeometryNodes()
   register_node_type_geo_curve_trim();
   register_node_type_geo_delete_geometry();
   register_node_type_geo_edge_split();
+  register_node_type_geo_input_index();
   register_node_type_geo_input_material();
+  register_node_type_geo_input_normal();
+  register_node_type_geo_input_position();
   register_node_type_geo_is_viewport();
   register_node_type_geo_join_geometry();
   register_node_type_geo_material_assign();
@@ -5202,6 +5206,7 @@ static void registerGeometryNodes()
   register_node_type_geo_select_by_handle_type();
   register_node_type_geo_select_by_material();
   register_node_type_geo_separate_components();
+  register_node_type_geo_set_position();
   register_node_type_geo_subdivision_surface();
   register_node_type_geo_switch();
   register_node_type_geo_transform();

source/blender/editors/space_spreadsheet/spreadsheet_data_source_geometry.cc

@@ -45,15 +45,20 @@ namespace blender::ed::spreadsheet {
 void GeometryDataSource::foreach_default_column_ids(
     FunctionRef<void(const SpreadsheetColumnID &)> fn) const
 {
-  component_->attribute_foreach([&](StringRefNull name, const AttributeMetaData &meta_data) {
-    if (meta_data.domain != domain_) {
-      return true;
-    }
-    SpreadsheetColumnID column_id;
-    column_id.name = (char *)name.c_str();
-    fn(column_id);
-    return true;
-  });
+  component_->attribute_foreach(
+      [&](const bke::AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        if (meta_data.domain != domain_) {
+          return true;
+        }
+        if (attribute_id.is_anonymous()) {
+          return true;
+        }
+        SpreadsheetColumnID column_id;
+        std::string name = attribute_id.name();
+        column_id.name = (char *)name.c_str();
+        fn(column_id);
+        return true;
+      });
 }
 
 std::unique_ptr<ColumnValues> GeometryDataSource::get_column_values(

source/blender/functions/CMakeLists.txt

@@ -28,14 +28,20 @@ set(INC_SYS
 
 set(SRC
   intern/cpp_types.cc
+  intern/field.cc
   intern/generic_vector_array.cc
   intern/generic_virtual_array.cc
   intern/generic_virtual_vector_array.cc
   intern/multi_function.cc
   intern/multi_function_builder.cc
+  intern/multi_function_procedure.cc
+  intern/multi_function_procedure_builder.cc
+  intern/multi_function_procedure_executor.cc
 
   FN_cpp_type.hh
   FN_cpp_type_make.hh
+  FN_field.hh
+  FN_field_cpp_type.hh
   FN_generic_pointer.hh
   FN_generic_span.hh
   FN_generic_value_map.hh
@@ -48,6 +54,9 @@ set(SRC
   FN_multi_function_data_type.hh
   FN_multi_function_param_type.hh
   FN_multi_function_params.hh
+  FN_multi_function_procedure.hh
+  FN_multi_function_procedure_builder.hh
+  FN_multi_function_procedure_executor.hh
   FN_multi_function_signature.hh
 )
 
@@ -60,8 +69,10 @@ blender_add_lib(bf_functions "${SRC}" "${INC}" "${INC_SYS}" "${LIB}")
 if(WITH_GTESTS)
   set(TEST_SRC
     tests/FN_cpp_type_test.cc
+    tests/FN_field_test.cc
     tests/FN_generic_span_test.cc
     tests/FN_generic_vector_array_test.cc
+    tests/FN_multi_function_procedure_test.cc
     tests/FN_multi_function_test.cc
   )
   set(TEST_LIB

source/blender/functions/FN_field.hh

@@ -0,0 +1,456 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup fn
+ *
+ * A #Field represents a function that outputs a value based on an arbitrary number of inputs. The
+ * inputs for a specific field evaluation are provided by a #FieldContext.
+ *
+ * A typical example is a field that computes a displacement vector for every vertex on a mesh
+ * based on its position.
+ *
+ * Fields can be build, composed and evaluated at run-time. They are stored in a directed tree
+ * graph data structure, whereby each node is a #FieldNode and edges are dependencies. A #FieldNode
+ * has an arbitrary number of inputs and at least one output and a #Field references a specific
+ * output of a #FieldNode. The inputs of a #FieldNode are other fields.
+ *
+ * There are two different types of field nodes:
+ *  - #FieldInput: Has no input and exactly one output. It represents an input to the entire field
+ *    when it is evaluated. During evaluation, the value of this input is based on a #FieldContext.
+ *  - #FieldOperation: Has an arbitrary number of field inputs and at least one output. Its main
+ *    use is to compose multiple existing fields into new fields.
+ *
+ * When fields are evaluated, they are converted into a multi-function procedure which allows
+ * efficient compution. In the future, we might support different field evaluation mechanisms for
+ * e.g. the following scenarios:
+ *  - Latency of a single evaluation is more important than throughput.
+ *  - Evaluation should happen on other hardware like GPUs.
+ *
+ * Whenever possible, multiple fields should be evaluated together to avoid duplicate work when
+ * they share common sub-fields and a common context.
+ */
+
+#include "BLI_string_ref.hh"
+#include "BLI_vector.hh"
+
+#include "FN_generic_virtual_array.hh"
+#include "FN_multi_function_builder.hh"
+#include "FN_multi_function_procedure.hh"
+#include "FN_multi_function_procedure_builder.hh"
+#include "FN_multi_function_procedure_executor.hh"
+
+namespace blender::fn {
+
+/**
+ * A node in a field-tree. It has at least one output that can be referenced by fields.
+ */
+class FieldNode {
+ private:
+  bool is_input_;
+
+ public:
+  FieldNode(bool is_input) : is_input_(is_input)
+  {
+  }
+
+  ~FieldNode() = default;
+
+  virtual const CPPType &output_cpp_type(int output_index) const = 0;
+
+  bool is_input() const
+  {
+    return is_input_;
+  }
+
+  bool is_operation() const
+  {
+    return !is_input_;
+  }
+
+  virtual uint64_t hash() const
+  {
+    return get_default_hash(this);
+  }
+
+  friend bool operator==(const FieldNode &a, const FieldNode &b)
+  {
+    return a.is_equal_to(b);
+  }
+
+  virtual bool is_equal_to(const FieldNode &other) const
+  {
+    return this == &other;
+  }
+};
+
+/**
+ * Common base class for fields to avoid declaring the same methods for #GField and #GFieldRef.
+ */
+template<typename NodePtr> class GFieldBase {
+ protected:
+  NodePtr node_ = nullptr;
+  int node_output_index_ = 0;
+
+  GFieldBase(NodePtr node, const int node_output_index)
+      : node_(std::move(node)), node_output_index_(node_output_index)
+  {
+  }
+
+ public:
+  GFieldBase() = default;
+
+  operator bool() const
+  {
+    return node_ != nullptr;
+  }
+
+  friend bool operator==(const GFieldBase &a, const GFieldBase &b)
+  {
+    return &*a.node_ == &*b.node_ && a.node_output_index_ == b.node_output_index_;
+  }
+
+  uint64_t hash() const
+  {
+    return get_default_hash_2(node_, node_output_index_);
+  }
+
+  const fn::CPPType &cpp_type() const
+  {
+    return node_->output_cpp_type(node_output_index_);
+  }
+
+  const FieldNode &node() const
+  {
+    return *node_;
+  }
+
+  int node_output_index() const
+  {
+    return node_output_index_;
+  }
+};
+
+/**
+ * A field whose output type is only known at run-time.
+ */
+class GField : public GFieldBase<std::shared_ptr<FieldNode>> {
+ public:
+  GField() = default;
+
+  GField(std::shared_ptr<FieldNode> node, const int node_output_index = 0)
+      : GFieldBase<std::shared_ptr<FieldNode>>(std::move(node), node_output_index)
+  {
+  }
+};
+
+/**
+ * Same as #GField but is cheaper to copy/move around, because it does not contain a
+ * #std::shared_ptr.
+ */
+class GFieldRef : public GFieldBase<const FieldNode *> {
+ public:
+  GFieldRef() = default;
+
+  GFieldRef(const GField &field)
+      : GFieldBase<const FieldNode *>(&field.node(), field.node_output_index())
+  {
+  }
+
+  GFieldRef(const FieldNode &node, const int node_output_index = 0)
+      : GFieldBase<const FieldNode *>(&node, node_output_index)
+  {
+  }
+};
+
+/**
+ * A typed version of #GField. It has the same memory layout as #GField.
+ */
+template<typename T> class Field : public GField {
+ public:
+  Field() = default;
+
+  Field(GField field) : GField(std::move(field))
+  {
+    BLI_assert(this->cpp_type().template is<T>());
+  }
+
+  Field(std::shared_ptr<FieldNode> node, const int node_output_index = 0)
+      : Field(GField(std::move(node), node_output_index))
+  {
+  }
+};
+
+/**
+ * A #FieldNode that allows composing existing fields into new fields.
+ */
+class FieldOperation : public FieldNode {
+  /**
+   * The multi-function used by this node. It is optionally owned.
+   * Multi-functions with mutable or vector parameters are not supported currently.
+   */
+  std::unique_ptr<const MultiFunction> owned_function_;
+  const MultiFunction *function_;
+
+  /** Inputs to the operation. */
+  blender::Vector<GField> inputs_;
+
+ public:
+  FieldOperation(std::unique_ptr<const MultiFunction> function, Vector<GField> inputs = {})
+      : FieldNode(false), owned_function_(std::move(function)), inputs_(std::move(inputs))
+  {
+    function_ = owned_function_.get();
+  }
+
+  FieldOperation(const MultiFunction &function, Vector<GField> inputs = {})
+      : FieldNode(false), function_(&function), inputs_(std::move(inputs))
+  {
+  }
+
+  Span<GField> inputs() const
+  {
+    return inputs_;
+  }
+
+  const MultiFunction &multi_function() const
+  {
+    return *function_;
+  }
+
+  const CPPType &output_cpp_type(int output_index) const override
+  {
+    int output_counter = 0;
+    for (const int param_index : function_->param_indices()) {
+      MFParamType param_type = function_->param_type(param_index);
+      if (param_type.is_output()) {
+        if (output_counter == output_index) {
+          return param_type.data_type().single_type();
+        }
+        output_counter++;
+      }
+    }
+    BLI_assert_unreachable();
+    return CPPType::get<float>();
+  }
+};
+
+class FieldContext;
+
+/**
+ * A #FieldNode that represents an input to the entire field-tree.
+ */
+class FieldInput : public FieldNode {
+ protected:
+  const CPPType *type_;
+  std::string debug_name_;
+
+ public:
+  FieldInput(const CPPType &type, std::string debug_name = "")
+      : FieldNode(true), type_(&type), debug_name_(std::move(debug_name))
+  {
+  }
+
+  /**
+   * Get the value of this specific input based on the given context. The returned virtual array,
+   * should live at least as long as the passed in #scope. May return null.
+   */
+  virtual const GVArray *get_varray_for_context(const FieldContext &context,
+                                                IndexMask mask,
+                                                ResourceScope &scope) const = 0;
+
+  blender::StringRef debug_name() const
+  {
+    return debug_name_;
+  }
+
+  const CPPType &cpp_type() const
+  {
+    return *type_;
+  }
+
+  const CPPType &output_cpp_type(int output_index) const override
+  {
+    BLI_assert(output_index == 0);
+    UNUSED_VARS_NDEBUG(output_index);
+    return *type_;
+  }
+};
+
+/**
+ * Provides inputs for a specific field evaluation.
+ */
+class FieldContext {
+ public:
+  ~FieldContext() = default;
+
+  virtual const GVArray *get_varray_for_input(const FieldInput &field_input,
+                                              IndexMask mask,
+                                              ResourceScope &scope) const;
+};
+
+/**
+ * Utility class that makes it easier to evaluate fields.
+ */
+class FieldEvaluator : NonMovable, NonCopyable {
+ private:
+  struct OutputPointerInfo {
+    void *dst = nullptr;
+    /* When a destination virtual array is provided for an input, this is
+     * unnecessary, otherwise this is used to construct the required virtual array. */
+    void (*set)(void *dst, const GVArray &varray, ResourceScope &scope) = nullptr;
+  };
+
+  ResourceScope scope_;
+  const FieldContext &context_;
+  const IndexMask mask_;
+  Vector<GField> fields_to_evaluate_;
+  Vector<GVMutableArray *> dst_varrays_;
+  Vector<const GVArray *> evaluated_varrays_;
+  Vector<OutputPointerInfo> output_pointer_infos_;
+  bool is_evaluated_ = false;
+
+ public:
+  /** Takes #mask by pointer because the mask has to live longer than the evaluator. */
+  FieldEvaluator(const FieldContext &context, const IndexMask *mask)
+      : context_(context), mask_(*mask)
+  {
+  }
+
+  /** Construct a field evaluator for all indices less than #size. */
+  FieldEvaluator(const FieldContext &context, const int64_t size) : context_(context), mask_(size)
+  {
+  }
+
+  ~FieldEvaluator()
+  {
+    /* While this assert isn't strictly necessary, and could be replaced with a warning,
+     * it will catch cases where someone forgets to call #evaluate(). */
+    BLI_assert(is_evaluated_);
+  }
+
+  /**
+   * \param field: Field to add to the evaluator.
+   * \param dst: Mutable virtual array that the evaluated result for this field is be written into.
+   */
+  int add_with_destination(GField field, GVMutableArray &dst);
+
+  /** Same as #add_with_destination but typed. */
+  template<typename T> int add_with_destination(Field<T> field, VMutableArray<T> &dst)
+  {
+    GVMutableArray &varray = scope_.construct<GVMutableArray_For_VMutableArray<T>>(__func__, dst);
+    return this->add_with_destination(GField(std::move(field)), varray);
+  }
+
+  /**
+   * \param field: Field to add to the evaluator.
+   * \param dst: Mutable span that the evaluated result for this field is be written into.
+   * \note: When the output may only be used as a single value, the version of this function with
+   * a virtual array result array should be used.
+   */
+  int add_with_destination(GField field, GMutableSpan dst);
+
+  /**
+   * \param field: Field to add to the evaluator.
+   * \param dst: Mutable span that the evaluated result for this field is be written into.
+   * \note: When the output may only be used as a single value, the version of this function with
+   * a virtual array result array should be used.
+   */
+  template<typename T> int add_with_destination(Field<T> field, MutableSpan<T> dst)
+  {
+    GVMutableArray &varray = scope_.construct<GVMutableArray_For_MutableSpan<T>>(__func__, dst);
+    return this->add_with_destination(std::move(field), varray);
+  }
+
+  int add(GField field, const GVArray **varray_ptr);
+
+  /**
+   * \param field: Field to add to the evaluator.
+   * \param varray_ptr: Once #evaluate is called, the resulting virtual array will be will be
+   *   assigned to the given position.
+   * \return Index of the field in the evaluator which can be used in the #get_evaluated methods.
+   */
+  template<typename T> int add(Field<T> field, const VArray<T> **varray_ptr)
+  {
+    const int field_index = fields_to_evaluate_.append_and_get_index(std::move(field));
+    dst_varrays_.append(nullptr);
+    output_pointer_infos_.append(OutputPointerInfo{
+        varray_ptr, [](void *dst, const GVArray &varray, ResourceScope &scope) {
+          *(const VArray<T> **)dst = &*scope.construct<GVArray_Typed<T>>(__func__, varray);
+        }});
+    return field_index;
+  }
+
+  /**
+   * \return Index of the field in the evaluator which can be used in the #get_evaluated methods.
+   */
+  int add(GField field);
+
+  /**
+   * Evaluate all fields on the evaluator. This can only be called once.
+   */
+  void evaluate();
+
+  const GVArray &get_evaluated(const int field_index) const
+  {
+    BLI_assert(is_evaluated_);
+    return *evaluated_varrays_[field_index];
+  }
+
+  template<typename T> const VArray<T> &get_evaluated(const int field_index)
+  {
+    const GVArray &varray = this->get_evaluated(field_index);
+    GVArray_Typed<T> &typed_varray = scope_.construct<GVArray_Typed<T>>(__func__, varray);
+    return *typed_varray;
+  }
+
+  /**
+   * Retrieve the output of an evaluated boolean field and convert it to a mask, which can be used
+   * to avoid calculations for unnecessary elements later on. The evaluator will own the indices in
+   * some cases, so it must live at least as long as the returned mask.
+   */
+  IndexMask get_evaluated_as_mask(const int field_index);
+};
+
+Vector<const GVArray *> evaluate_fields(ResourceScope &scope,
+                                        Span<GFieldRef> fields_to_evaluate,
+                                        IndexMask mask,
+                                        const FieldContext &context,
+                                        Span<GVMutableArray *> dst_varrays = {});
+
+/* --------------------------------------------------------------------
+ * Utility functions for simple field creation and evaluation.
+ */
+
+void evaluate_constant_field(const GField &field, void *r_value);
+
+template<typename T> T evaluate_constant_field(const Field<T> &field)
+{
+  T value;
+  value.~T();
+  evaluate_constant_field(field, &value);
+  return value;
+}
+
+template<typename T> Field<T> make_constant_field(T value)
+{
+  auto constant_fn = std::make_unique<fn::CustomMF_Constant<T>>(std::forward<T>(value));
+  auto operation = std::make_shared<FieldOperation>(std::move(constant_fn));
+  return Field<T>{GField{std::move(operation), 0}};
+}
+
+}  // namespace blender::fn

source/blender/functions/FN_field_cpp_type.hh

@@ -0,0 +1,72 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup fn
+ */
+
+#include "FN_cpp_type_make.hh"
+#include "FN_field.hh"
+
+namespace blender::fn {
+
+template<typename T> struct FieldCPPTypeParam {
+};
+
+class FieldCPPType : public CPPType {
+ private:
+  const CPPType &field_type_;
+
+ public:
+  template<typename T>
+  FieldCPPType(FieldCPPTypeParam<Field<T>> /* unused */, StringRef debug_name)
+      : CPPType(CPPTypeParam<Field<T>, CPPTypeFlags::None>(), debug_name),
+        field_type_(CPPType::get<T>())
+  {
+  }
+
+  const CPPType &field_type() const
+  {
+    return field_type_;
+  }
+
+  /* Ensure that #GField and #Field<T> have the same layout, to enable casting between the two. */
+  static_assert(sizeof(Field<int>) == sizeof(GField));
+  static_assert(sizeof(Field<int>) == sizeof(Field<std::string>));
+
+  const GField &get_gfield(const void *field) const
+  {
+    return *(const GField *)field;
+  }
+
+  void construct_from_gfield(void *r_value, const GField &gfield) const
+  {
+    new (r_value) GField(gfield);
+  }
+};
+
+}  // namespace blender::fn
+
+#define MAKE_FIELD_CPP_TYPE(DEBUG_NAME, FIELD_TYPE) \
+  template<> \
+  const blender::fn::CPPType &blender::fn::CPPType::get_impl<blender::fn::Field<FIELD_TYPE>>() \
+  { \
+    static blender::fn::FieldCPPType cpp_type{ \
+        blender::fn::FieldCPPTypeParam<blender::fn::Field<FIELD_TYPE>>(), STRINGIFY(DEBUG_NAME)}; \
+    return cpp_type; \
+  }

source/blender/functions/FN_multi_function_builder.hh

@@ -417,4 +417,13 @@ class CustomMF_DefaultOutput : public MultiFunction {
   void call(IndexMask mask, MFParams params, MFContext context) const override;
 };
 
+class CustomMF_GenericCopy : public MultiFunction {
+ private:
+  MFSignature signature_;
+
+ public:
+  CustomMF_GenericCopy(StringRef name, MFDataType data_type);
+  void call(IndexMask mask, MFParams params, MFContext context) const override;
+};
+
 }  // namespace blender::fn

source/blender/functions/FN_multi_function_params.hh

@@ -195,7 +195,7 @@ class MFParams {
   template<typename T> const VArray<T> &readonly_single_input(int param_index, StringRef name = "")
   {
     const GVArray &array = this->readonly_single_input(param_index, name);
-    return builder_->scope_.construct<VArray_For_GVArray<T>>(__func__, array);
+    return builder_->scope_.construct<GVArray_Typed<T>>(__func__, array);
   }
   const GVArray &readonly_single_input(int param_index, StringRef name = "")
   {

source/blender/functions/FN_multi_function_procedure.hh

@@ -0,0 +1,452 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup fn
+ */
+
+#include "FN_multi_function.hh"
+
+namespace blender::fn {
+
+class MFVariable;
+class MFInstruction;
+class MFCallInstruction;
+class MFBranchInstruction;
+class MFDestructInstruction;
+class MFDummyInstruction;
+class MFReturnInstruction;
+class MFProcedure;
+
+/** Every instruction has exactly one of these types. */
+enum class MFInstructionType {
+  Call,
+  Branch,
+  Destruct,
+  Dummy,
+  Return,
+};
+
+/**
+ * A variable is similar to a virtual register in other libraries. During evaluation, every is
+ * either uninitialized or contains a value for every index (remember, a multi-function procedure
+ * is always evaluated for many indices at the same time).
+ */
+class MFVariable : NonCopyable, NonMovable {
+ private:
+  MFDataType data_type_;
+  Vector<MFInstruction *> users_;
+  std::string name_;
+  int id_;
+
+  friend MFProcedure;
+  friend MFCallInstruction;
+  friend MFBranchInstruction;
+  friend MFDestructInstruction;
+
+ public:
+  MFDataType data_type() const;
+  Span<MFInstruction *> users();
+
+  StringRefNull name() const;
+  void set_name(std::string name);
+
+  int id() const;
+};
+
+/** Base class for all instruction types. */
+class MFInstruction : NonCopyable, NonMovable {
+ protected:
+  MFInstructionType type_;
+  Vector<MFInstruction *> prev_;
+
+  friend MFProcedure;
+  friend MFCallInstruction;
+  friend MFBranchInstruction;
+  friend MFDestructInstruction;
+  friend MFDummyInstruction;
+  friend MFReturnInstruction;
+
+ public:
+  MFInstructionType type() const;
+
+  /**
+   * Other instructions that come before this instruction. There can be multiple previous
+   * instructions when branching is used in the procedure.
+   */
+  Span<MFInstruction *> prev();
+  Span<const MFInstruction *> prev() const;
+};
+
+/**
+ * References a multi-function that is evaluated when the instruction is executed. It also
+ * references the variables whose data will be passed into the multi-function.
+ */
+class MFCallInstruction : public MFInstruction {
+ private:
+  const MultiFunction *fn_ = nullptr;
+  MFInstruction *next_ = nullptr;
+  MutableSpan<MFVariable *> params_;
+
+  friend MFProcedure;
+
+ public:
+  const MultiFunction &fn() const;
+
+  MFInstruction *next();
+  const MFInstruction *next() const;
+  void set_next(MFInstruction *instruction);
+
+  void set_param_variable(int param_index, MFVariable *variable);
+  void set_params(Span<MFVariable *> variables);
+
+  Span<MFVariable *> params();
+  Span<const MFVariable *> params() const;
+};
+
+/**
+ * What makes a branch instruction special is that it has two successor instructions. One that will
+ * be used when a condition variable was true, and one otherwise.
+ */
+class MFBranchInstruction : public MFInstruction {
+ private:
+  MFVariable *condition_ = nullptr;
+  MFInstruction *branch_true_ = nullptr;
+  MFInstruction *branch_false_ = nullptr;
+
+  friend MFProcedure;
+
+ public:
+  MFVariable *condition();
+  const MFVariable *condition() const;
+  void set_condition(MFVariable *variable);
+
+  MFInstruction *branch_true();
+  const MFInstruction *branch_true() const;
+  void set_branch_true(MFInstruction *instruction);
+
+  MFInstruction *branch_false();
+  const MFInstruction *branch_false() const;
+  void set_branch_false(MFInstruction *instruction);
+};
+
+/**
+ * A destruct instruction destructs a single variable. So the variable value will be uninitialized
+ * after this instruction. All variables that are not output variables of the procedure, have to be
+ * destructed before the procedure ends. Destructing early is generally a good thing, because it
+ * might help with memory buffer reuse, which decreases memory-usage and increases performance.
+ */
+class MFDestructInstruction : public MFInstruction {
+ private:
+  MFVariable *variable_ = nullptr;
+  MFInstruction *next_ = nullptr;
+
+  friend MFProcedure;
+
+ public:
+  MFVariable *variable();
+  const MFVariable *variable() const;
+  void set_variable(MFVariable *variable);
+
+  MFInstruction *next();
+  const MFInstruction *next() const;
+  void set_next(MFInstruction *instruction);
+};
+
+/**
+ * This instruction does nothing, it just exists to building a procedure simpler in some cases.
+ */
+class MFDummyInstruction : public MFInstruction {
+ private:
+  MFInstruction *next_ = nullptr;
+
+  friend MFProcedure;
+
+ public:
+  MFInstruction *next();
+  const MFInstruction *next() const;
+  void set_next(MFInstruction *instruction);
+};
+
+/**
+ * This instruction ends the procedure.
+ */
+class MFReturnInstruction : public MFInstruction {
+};
+
+/**
+ * Inputs and outputs of the entire procedure network.
+ */
+struct MFParameter {
+  MFParamType::InterfaceType type;
+  MFVariable *variable;
+};
+
+struct ConstMFParameter {
+  MFParamType::InterfaceType type;
+  const MFVariable *variable;
+};
+
+/**
+ * A multi-function procedure allows composing multi-functions in arbitrary ways. It consists of
+ * variables and instructions that operate on those variables. Branching and looping within the
+ * procedure is supported as well.
+ *
+ * Typically, a #MFProcedure should be constructed using a #MFProcedureBuilder, which has many more
+ * utility methods for common use cases.
+ */
+class MFProcedure : NonCopyable, NonMovable {
+ private:
+  LinearAllocator<> allocator_;
+  Vector<MFCallInstruction *> call_instructions_;
+  Vector<MFBranchInstruction *> branch_instructions_;
+  Vector<MFDestructInstruction *> destruct_instructions_;
+  Vector<MFDummyInstruction *> dummy_instructions_;
+  Vector<MFReturnInstruction *> return_instructions_;
+  Vector<MFVariable *> variables_;
+  Vector<MFParameter> params_;
+  MFInstruction *entry_ = nullptr;
+
+  friend class MFProcedureDotExport;
+
+ public:
+  MFProcedure() = default;
+  ~MFProcedure();
+
+  MFVariable &new_variable(MFDataType data_type, std::string name = "");
+  MFCallInstruction &new_call_instruction(const MultiFunction &fn);
+  MFBranchInstruction &new_branch_instruction();
+  MFDestructInstruction &new_destruct_instruction();
+  MFDummyInstruction &new_dummy_instruction();
+  MFReturnInstruction &new_return_instruction();
+
+  void add_parameter(MFParamType::InterfaceType interface_type, MFVariable &variable);
+
+  Span<ConstMFParameter> params() const;
+
+  MFInstruction *entry();
+  const MFInstruction *entry() const;
+  void set_entry(MFInstruction &entry);
+
+  Span<MFVariable *> variables();
+  Span<const MFVariable *> variables() const;
+
+  std::string to_dot() const;
+
+  bool validate() const;
+
+ private:
+  bool validate_all_instruction_pointers_set() const;
+  bool validate_all_params_provided() const;
+  bool validate_same_variables_in_one_call() const;
+  bool validate_parameters() const;
+  bool validate_initialization() const;
+
+  struct InitState {
+    bool can_be_initialized = false;
+    bool can_be_uninitialized = false;
+  };
+
+  InitState find_initialization_state_before_instruction(const MFInstruction &target_instruction,
+                                                         const MFVariable &variable) const;
+};
+
+namespace multi_function_procedure_types {
+using MFVariable = fn::MFVariable;
+using MFInstruction = fn::MFInstruction;
+using MFCallInstruction = fn::MFCallInstruction;
+using MFBranchInstruction = fn::MFBranchInstruction;
+using MFDestructInstruction = fn::MFDestructInstruction;
+using MFProcedure = fn::MFProcedure;
+}  // namespace multi_function_procedure_types
+
+/* --------------------------------------------------------------------
+ * MFVariable inline methods.
+ */
+
+inline MFDataType MFVariable::data_type() const
+{
+  return data_type_;
+}
+
+inline Span<MFInstruction *> MFVariable::users()
+{
+  return users_;
+}
+
+inline StringRefNull MFVariable::name() const
+{
+  return name_;
+}
+
+inline int MFVariable::id() const
+{
+  return id_;
+}
+
+/* --------------------------------------------------------------------
+ * MFInstruction inline methods.
+ */
+
+inline MFInstructionType MFInstruction::type() const
+{
+  return type_;
+}
+
+inline Span<MFInstruction *> MFInstruction::prev()
+{
+  return prev_;
+}
+
+inline Span<const MFInstruction *> MFInstruction::prev() const
+{
+  return prev_;
+}
+
+/* --------------------------------------------------------------------
+ * MFCallInstruction inline methods.
+ */
+
+inline const MultiFunction &MFCallInstruction::fn() const
+{
+  return *fn_;
+}
+
+inline MFInstruction *MFCallInstruction::next()
+{
+  return next_;
+}
+
+inline const MFInstruction *MFCallInstruction::next() const
+{
+  return next_;
+}
+
+inline Span<MFVariable *> MFCallInstruction::params()
+{
+  return params_;
+}
+
+inline Span<const MFVariable *> MFCallInstruction::params() const
+{
+  return params_;
+}
+
+/* --------------------------------------------------------------------
+ * MFBranchInstruction inline methods.
+ */
+
+inline MFVariable *MFBranchInstruction::condition()
+{
+  return condition_;
+}
+
+inline const MFVariable *MFBranchInstruction::condition() const
+{
+  return condition_;
+}
+
+inline MFInstruction *MFBranchInstruction::branch_true()
+{
+  return branch_true_;
+}
+
+inline const MFInstruction *MFBranchInstruction::branch_true() const
+{
+  return branch_true_;
+}
+
+inline MFInstruction *MFBranchInstruction::branch_false()
+{
+  return branch_false_;
+}
+
+inline const MFInstruction *MFBranchInstruction::branch_false() const
+{
+  return branch_false_;
+}
+
+/* --------------------------------------------------------------------
+ * MFDestructInstruction inline methods.
+ */
+
+inline MFVariable *MFDestructInstruction::variable()
+{
+  return variable_;
+}
+
+inline const MFVariable *MFDestructInstruction::variable() const
+{
+  return variable_;
+}
+
+inline MFInstruction *MFDestructInstruction::next()
+{
+  return next_;
+}
+
+inline const MFInstruction *MFDestructInstruction::next() const
+{
+  return next_;
+}
+
+/* --------------------------------------------------------------------
+ * MFDummyInstruction inline methods.
+ */
+
+inline MFInstruction *MFDummyInstruction::next()
+{
+  return next_;
+}
+
+inline const MFInstruction *MFDummyInstruction::next() const
+{
+  return next_;
+}
+
+/* --------------------------------------------------------------------
+ * MFProcedure inline methods.
+ */
+
+inline Span<ConstMFParameter> MFProcedure::params() const
+{
+  static_assert(sizeof(MFParameter) == sizeof(ConstMFParameter));
+  return params_.as_span().cast<ConstMFParameter>();
+}
+
+inline MFInstruction *MFProcedure::entry()
+{
+  return entry_;
+}
+
+inline const MFInstruction *MFProcedure::entry() const
+{
+  return entry_;
+}
+
+inline Span<MFVariable *> MFProcedure::variables()
+{
+  return variables_;
+}
+
+inline Span<const MFVariable *> MFProcedure::variables() const
+{
+  return variables_;
+}
+
+}  // namespace blender::fn

source/blender/functions/FN_multi_function_procedure_builder.hh

@@ -0,0 +1,260 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup fn
+ */
+
+#include "FN_multi_function_procedure.hh"
+
+namespace blender::fn {
+
+/**
+ * An #MFInstructionCursor points to a position in a multi-function procedure, where an instruction
+ * can be inserted.
+ */
+class MFInstructionCursor {
+ private:
+  MFInstruction *instruction_ = nullptr;
+  /* Only used when it is a branch instruction. */
+  bool branch_output_ = false;
+  /* Only used when instruction is null. */
+  bool is_entry_ = false;
+
+ public:
+  MFInstructionCursor() = default;
+
+  MFInstructionCursor(MFCallInstruction &instruction);
+  MFInstructionCursor(MFDestructInstruction &instruction);
+  MFInstructionCursor(MFBranchInstruction &instruction, bool branch_output);
+  MFInstructionCursor(MFDummyInstruction &instruction);
+
+  static MFInstructionCursor Entry();
+
+  void insert(MFProcedure &procedure, MFInstruction *new_instruction);
+};
+
+/**
+ * Utility class to build a #MFProcedure.
+ */
+class MFProcedureBuilder {
+ private:
+  /** Procedure that is being build. */
+  MFProcedure *procedure_ = nullptr;
+  /** Cursors where the next instruction should be inserted. */
+  Vector<MFInstructionCursor> cursors_;
+
+ public:
+  struct Branch;
+  struct Loop;
+
+  MFProcedureBuilder(MFProcedure &procedure,
+                     MFInstructionCursor initial_cursor = MFInstructionCursor::Entry());
+
+  MFProcedureBuilder(Span<MFProcedureBuilder *> builders);
+
+  MFProcedureBuilder(Branch &branch);
+
+  void set_cursor(const MFInstructionCursor &cursor);
+  void set_cursor(Span<MFInstructionCursor> cursors);
+  void set_cursor(Span<MFProcedureBuilder *> builders);
+  void set_cursor_after_branch(Branch &branch);
+  void set_cursor_after_loop(Loop &loop);
+
+  void add_destruct(MFVariable &variable);
+  void add_destruct(Span<MFVariable *> variables);
+
+  MFReturnInstruction &add_return();
+
+  Branch add_branch(MFVariable &condition);
+
+  Loop add_loop();
+  void add_loop_continue(Loop &loop);
+  void add_loop_break(Loop &loop);
+
+  MFCallInstruction &add_call_with_no_variables(const MultiFunction &fn);
+  MFCallInstruction &add_call_with_all_variables(const MultiFunction &fn,
+                                                 Span<MFVariable *> param_variables);
+
+  Vector<MFVariable *> add_call(const MultiFunction &fn,
+                                Span<MFVariable *> input_and_mutable_variables = {});
+
+  template<int OutputN>
+  std::array<MFVariable *, OutputN> add_call(const MultiFunction &fn,
+                                             Span<MFVariable *> input_and_mutable_variables = {});
+
+  void add_parameter(MFParamType::InterfaceType interface_type, MFVariable &variable);
+  MFVariable &add_parameter(MFParamType param_type, std::string name = "");
+
+  MFVariable &add_input_parameter(MFDataType data_type, std::string name = "");
+  template<typename T> MFVariable &add_single_input_parameter(std::string name = "");
+  template<typename T> MFVariable &add_single_mutable_parameter(std::string name = "");
+
+  void add_output_parameter(MFVariable &variable);
+
+ private:
+  void link_to_cursors(MFInstruction *instruction);
+};
+
+struct MFProcedureBuilder::Branch {
+  MFProcedureBuilder branch_true;
+  MFProcedureBuilder branch_false;
+};
+
+struct MFProcedureBuilder::Loop {
+  MFInstruction *begin = nullptr;
+  MFDummyInstruction *end = nullptr;
+};
+
+/* --------------------------------------------------------------------
+ * MFInstructionCursor inline methods.
+ */
+
+inline MFInstructionCursor::MFInstructionCursor(MFCallInstruction &instruction)
+    : instruction_(&instruction)
+{
+}
+
+inline MFInstructionCursor::MFInstructionCursor(MFDestructInstruction &instruction)
+    : instruction_(&instruction)
+{
+}
+
+inline MFInstructionCursor::MFInstructionCursor(MFBranchInstruction &instruction,
+                                                bool branch_output)
+    : instruction_(&instruction), branch_output_(branch_output)
+{
+}
+
+inline MFInstructionCursor::MFInstructionCursor(MFDummyInstruction &instruction)
+    : instruction_(&instruction)
+{
+}
+
+inline MFInstructionCursor MFInstructionCursor::Entry()
+{
+  MFInstructionCursor cursor;
+  cursor.is_entry_ = true;
+  return cursor;
+}
+
+/* --------------------------------------------------------------------
+ * MFProcedureBuilder inline methods.
+ */
+
+inline MFProcedureBuilder::MFProcedureBuilder(Branch &branch)
+    : MFProcedureBuilder(*branch.branch_true.procedure_)
+{
+  this->set_cursor_after_branch(branch);
+}
+
+inline MFProcedureBuilder::MFProcedureBuilder(MFProcedure &procedure,
+                                              MFInstructionCursor initial_cursor)
+    : procedure_(&procedure), cursors_({initial_cursor})
+{
+}
+
+inline MFProcedureBuilder::MFProcedureBuilder(Span<MFProcedureBuilder *> builders)
+    : MFProcedureBuilder(*builders[0]->procedure_)
+{
+  this->set_cursor(builders);
+}
+
+inline void MFProcedureBuilder::set_cursor(const MFInstructionCursor &cursor)
+{
+  cursors_ = {cursor};
+}
+
+inline void MFProcedureBuilder::set_cursor(Span<MFInstructionCursor> cursors)
+{
+  cursors_ = cursors;
+}
+
+inline void MFProcedureBuilder::set_cursor_after_branch(Branch &branch)
+{
+  this->set_cursor({&branch.branch_false, &branch.branch_true});
+}
+
+inline void MFProcedureBuilder::set_cursor_after_loop(Loop &loop)
+{
+  this->set_cursor(MFInstructionCursor{*loop.end});
+}
+
+inline void MFProcedureBuilder::set_cursor(Span<MFProcedureBuilder *> builders)
+{
+  cursors_.clear();
+  for (MFProcedureBuilder *builder : builders) {
+    cursors_.extend(builder->cursors_);
+  }
+}
+
+template<int OutputN>
+inline std::array<MFVariable *, OutputN> MFProcedureBuilder::add_call(
+    const MultiFunction &fn, Span<MFVariable *> input_and_mutable_variables)
+{
+  Vector<MFVariable *> output_variables = this->add_call(fn, input_and_mutable_variables);
+  BLI_assert(output_variables.size() == OutputN);
+
+  std::array<MFVariable *, OutputN> output_array;
+  initialized_copy_n(output_variables.data(), OutputN, output_array.data());
+  return output_array;
+}
+
+inline void MFProcedureBuilder::add_parameter(MFParamType::InterfaceType interface_type,
+                                              MFVariable &variable)
+{
+  procedure_->add_parameter(interface_type, variable);
+}
+
+inline MFVariable &MFProcedureBuilder::add_parameter(MFParamType param_type, std::string name)
+{
+  MFVariable &variable = procedure_->new_variable(param_type.data_type(), std::move(name));
+  this->add_parameter(param_type.interface_type(), variable);
+  return variable;
+}
+
+inline MFVariable &MFProcedureBuilder::add_input_parameter(MFDataType data_type, std::string name)
+{
+  return this->add_parameter(MFParamType(MFParamType::Input, data_type), std::move(name));
+}
+
+template<typename T>
+inline MFVariable &MFProcedureBuilder::add_single_input_parameter(std::string name)
+{
+  return this->add_parameter(MFParamType::ForSingleInput(CPPType::get<T>()), std::move(name));
+}
+
+template<typename T>
+inline MFVariable &MFProcedureBuilder::add_single_mutable_parameter(std::string name)
+{
+  return this->add_parameter(MFParamType::ForMutableSingle(CPPType::get<T>()), std::move(name));
+}
+
+inline void MFProcedureBuilder::add_output_parameter(MFVariable &variable)
+{
+  this->add_parameter(MFParamType::Output, variable);
+}
+
+inline void MFProcedureBuilder::link_to_cursors(MFInstruction *instruction)
+{
+  for (MFInstructionCursor &cursor : cursors_) {
+    cursor.insert(*procedure_, instruction);
+  }
+}
+
+}  // namespace blender::fn

source/blender/functions/FN_multi_function_procedure_executor.hh

@@ -0,0 +1,39 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#pragma once
+
+/** \file
+ * \ingroup fn
+ */
+
+#include "FN_multi_function_procedure.hh"
+
+namespace blender::fn {
+
+/** A multi-function that executes a procedure internally. */
+class MFProcedureExecutor : public MultiFunction {
+ private:
+  MFSignature signature_;
+  const MFProcedure &procedure_;
+
+ public:
+  MFProcedureExecutor(std::string name, const MFProcedure &procedure);
+
+  void call(IndexMask mask, MFParams params, MFContext context) const override;
+};
+
+}  // namespace blender::fn

source/blender/functions/intern/cpp_types.cc

@@ -15,6 +15,7 @@
  */
 
 #include "FN_cpp_type_make.hh"
+#include "FN_field_cpp_type.hh"
 
 #include "BLI_color.hh"
 #include "BLI_float2.hh"
@@ -39,4 +40,12 @@ MAKE_CPP_TYPE(ColorGeometry4b, blender::ColorGeometry4b, CPPTypeFlags::BasicType
 
 MAKE_CPP_TYPE(string, std::string, CPPTypeFlags::BasicType)
 
+MAKE_FIELD_CPP_TYPE(FloatField, float);
+MAKE_FIELD_CPP_TYPE(Float2Field, float2);
+MAKE_FIELD_CPP_TYPE(Float3Field, float3);
+MAKE_FIELD_CPP_TYPE(ColorGeometry4fField, blender::ColorGeometry4f);
+MAKE_FIELD_CPP_TYPE(BoolField, bool);
+MAKE_FIELD_CPP_TYPE(Int32Field, int32_t);
+MAKE_FIELD_CPP_TYPE(StringField, std::string);
+
 }  // namespace blender::fn

source/blender/functions/intern/field.cc

@@ -0,0 +1,569 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "BLI_map.hh"
+#include "BLI_multi_value_map.hh"
+#include "BLI_set.hh"
+#include "BLI_stack.hh"
+#include "BLI_vector_set.hh"
+
+#include "FN_field.hh"
+
+namespace blender::fn {
+
+/* --------------------------------------------------------------------
+ * Field Evaluation.
+ */
+
+struct FieldTreeInfo {
+  /**
+   * When fields are built, they only have references to the fields that they depend on. This map
+   * allows traversal of fields in the opposite direction. So for every field it stores the other
+   * fields that depend on it directly.
+   */
+  MultiValueMap<GFieldRef, GFieldRef> field_users;
+  /**
+   * The same field input may exist in the field tree as as separate nodes due to the way
+   * the tree is constructed. This set contains every different input only once.
+   */
+  VectorSet<std::reference_wrapper<const FieldInput>> deduplicated_field_inputs;
+};
+
+/**
+ * Collects some information from the field tree that is required by later steps.
+ */
+static FieldTreeInfo preprocess_field_tree(Span<GFieldRef> entry_fields)
+{
+  FieldTreeInfo field_tree_info;
+
+  Stack<GFieldRef> fields_to_check;
+  Set<GFieldRef> handled_fields;
+
+  for (GFieldRef field : entry_fields) {
+    if (handled_fields.add(field)) {
+      fields_to_check.push(field);
+    }
+  }
+
+  while (!fields_to_check.is_empty()) {
+    GFieldRef field = fields_to_check.pop();
+    if (field.node().is_input()) {
+      const FieldInput &field_input = static_cast<const FieldInput &>(field.node());
+      field_tree_info.deduplicated_field_inputs.add(field_input);
+      continue;
+    }
+    BLI_assert(field.node().is_operation());
+    const FieldOperation &operation = static_cast<const FieldOperation &>(field.node());
+    for (const GFieldRef operation_input : operation.inputs()) {
+      field_tree_info.field_users.add(operation_input, field);
+      if (handled_fields.add(operation_input)) {
+        fields_to_check.push(operation_input);
+      }
+    }
+  }
+  return field_tree_info;
+}
+
+/**
+ * Retrieves the data from the context that is passed as input into the field.
+ */
+static Vector<const GVArray *> get_field_context_inputs(
+    ResourceScope &scope,
+    const IndexMask mask,
+    const FieldContext &context,
+    const Span<std::reference_wrapper<const FieldInput>> field_inputs)
+{
+  Vector<const GVArray *> field_context_inputs;
+  for (const FieldInput &field_input : field_inputs) {
+    const GVArray *varray = context.get_varray_for_input(field_input, mask, scope);
+    if (varray == nullptr) {
+      const CPPType &type = field_input.cpp_type();
+      varray = &scope.construct<GVArray_For_SingleValueRef>(
+          __func__, type, mask.min_array_size(), type.default_value());
+    }
+    field_context_inputs.append(varray);
+  }
+  return field_context_inputs;
+}
+
+/**
+ * \return A set that contains all fields from the field tree that depend on an input that varies
+ * for different indices.
+ */
+static Set<GFieldRef> find_varying_fields(const FieldTreeInfo &field_tree_info,
+                                          Span<const GVArray *> field_context_inputs)
+{
+  Set<GFieldRef> found_fields;
+  Stack<GFieldRef> fields_to_check;
+
+  /* The varying fields are the ones that depend on inputs that are not constant. Therefore we
+   * start the tree search at the non-constant input fields and traverse through all fields that
+   * depend on them. */
+  for (const int i : field_context_inputs.index_range()) {
+    const GVArray *varray = field_context_inputs[i];
+    if (varray->is_single()) {
+      continue;
+    }
+    const FieldInput &field_input = field_tree_info.deduplicated_field_inputs[i];
+    const GFieldRef field_input_field{field_input, 0};
+    const Span<GFieldRef> users = field_tree_info.field_users.lookup(field_input_field);
+    for (const GFieldRef &field : users) {
+      if (found_fields.add(field)) {
+        fields_to_check.push(field);
+      }
+    }
+  }
+  while (!fields_to_check.is_empty()) {
+    GFieldRef field = fields_to_check.pop();
+    const Span<GFieldRef> users = field_tree_info.field_users.lookup(field);
+    for (GFieldRef field : users) {
+      if (found_fields.add(field)) {
+        fields_to_check.push(field);
+      }
+    }
+  }
+  return found_fields;
+}
+
+/**
+ * Builds the #procedure so that it computes the the fields.
+ */
+static void build_multi_function_procedure_for_fields(MFProcedure &procedure,
+                                                      ResourceScope &scope,
+                                                      const FieldTreeInfo &field_tree_info,
+                                                      Span<GFieldRef> output_fields)
+{
+  MFProcedureBuilder builder{procedure};
+  /* Every input, intermediate and output field corresponds to a variable in the procedure. */
+  Map<GFieldRef, MFVariable *> variable_by_field;
+
+  /* Start by adding the field inputs as parameters to the procedure. */
+  for (const FieldInput &field_input : field_tree_info.deduplicated_field_inputs) {
+    MFVariable &variable = builder.add_input_parameter(
+        MFDataType::ForSingle(field_input.cpp_type()), field_input.debug_name());
+    variable_by_field.add_new({field_input, 0}, &variable);
+  }
+
+  /* Utility struct that is used to do proper depth first search traversal of the tree below. */
+  struct FieldWithIndex {
+    GFieldRef field;
+    int current_input_index = 0;
+  };
+
+  for (GFieldRef field : output_fields) {
+    /* We start a new stack for each output field to make sure that a field pushed later to the
+     * stack does never depend on a field that was pushed before. */
+    Stack<FieldWithIndex> fields_to_check;
+    fields_to_check.push({field, 0});
+    while (!fields_to_check.is_empty()) {
+      FieldWithIndex &field_with_index = fields_to_check.peek();
+      const GFieldRef &field = field_with_index.field;
+      if (variable_by_field.contains(field)) {
+        /* The field has been handled already. */
+        fields_to_check.pop();
+        continue;
+      }
+      /* Field inputs should already be handled above. */
+      BLI_assert(field.node().is_operation());
+
+      const FieldOperation &operation = static_cast<const FieldOperation &>(field.node());
+      const Span<GField> operation_inputs = operation.inputs();
+
+      if (field_with_index.current_input_index < operation_inputs.size()) {
+        /* Not all inputs are handled yet. Push the next input field to the stack and increment the
+         * input index. */
+        fields_to_check.push({operation_inputs[field_with_index.current_input_index]});
+        field_with_index.current_input_index++;
+      }
+      else {
+        /* All inputs variables are ready, now add the function call. */
+        Vector<MFVariable *> input_variables;
+        for (const GField &field : operation_inputs) {
+          input_variables.append(variable_by_field.lookup(field));
+        }
+        const MultiFunction &multi_function = operation.multi_function();
+        Vector<MFVariable *> output_variables = builder.add_call(multi_function, input_variables);
+        /* Add newly created variables to the map. */
+        for (const int i : output_variables.index_range()) {
+          variable_by_field.add_new({operation, i}, output_variables[i]);
+        }
+      }
+    }
+  }
+
+  /* Add output parameters to the procedure. */
+  Set<MFVariable *> already_output_variables;
+  for (const GFieldRef &field : output_fields) {
+    MFVariable *variable = variable_by_field.lookup(field);
+    if (!already_output_variables.add(variable)) {
+      /* One variable can be output at most once. To output the same value twice, we have to make
+       * a copy first. */
+      const MultiFunction &copy_fn = scope.construct<CustomMF_GenericCopy>(
+          __func__, "copy", variable->data_type());
+      variable = builder.add_call<1>(copy_fn, {variable})[0];
+    }
+    builder.add_output_parameter(*variable);
+  }
+
+  /* Remove the variables that should not be destructed from the map. */
+  for (const GFieldRef &field : output_fields) {
+    variable_by_field.remove(field);
+  }
+  /* Add destructor calls for the remaining variables. */
+  for (MFVariable *variable : variable_by_field.values()) {
+    builder.add_destruct(*variable);
+  }
+
+  builder.add_return();
+
+  // std::cout << procedure.to_dot() << "\n";
+  BLI_assert(procedure.validate());
+}
+
+/**
+ * Utility class that destructs elements from a partially initialized array.
+ */
+struct PartiallyInitializedArray : NonCopyable, NonMovable {
+  void *buffer;
+  IndexMask mask;
+  const CPPType *type;
+
+  ~PartiallyInitializedArray()
+  {
+    this->type->destruct_indices(this->buffer, this->mask);
+  }
+};
+
+/**
+ * Evaluate fields in the given context. If possible, multiple fields should be evaluated together,
+ * because that can be more efficient when they share common sub-fields.
+ *
+ * \param scope: The resource scope that owns data that makes up the output virtual arrays. Make
+ *   sure the scope is not destructed when the output virtual arrays are still used.
+ * \param fields_to_evaluate: The fields that should be evaluated together.
+ * \param mask: Determines which indices are computed. The mask may be referenced by the returned
+ *   virtual arrays. So the underlying indices (if applicable) should live longer then #scope.
+ * \param context: The context that the field is evaluated in. Used to retrieve data from each
+ *   #FieldInput in the field network.
+ * \param dst_varrays: If provided, the computed data will be written into those virtual arrays
+ *   instead of into newly created ones. That allows making the computed data live longer than
+ *   #scope and is more efficient when the data will be written into those virtual arrays
+ *   later anyway.
+ * \return The computed virtual arrays for each provided field. If #dst_varrays is passed, the
+ *   provided virtual arrays are returned.
+ */
+Vector<const GVArray *> evaluate_fields(ResourceScope &scope,
+                                        Span<GFieldRef> fields_to_evaluate,
+                                        IndexMask mask,
+                                        const FieldContext &context,
+                                        Span<GVMutableArray *> dst_varrays)
+{
+  Vector<const GVArray *> r_varrays(fields_to_evaluate.size(), nullptr);
+  const int array_size = mask.min_array_size();
+
+  /* Destination arrays are optional. Create a small utility method to access them. */
+  auto get_dst_varray_if_available = [&](int index) -> GVMutableArray * {
+    if (dst_varrays.is_empty()) {
+      return nullptr;
+    }
+    BLI_assert(dst_varrays[index] == nullptr || dst_varrays[index]->size() >= array_size);
+    return dst_varrays[index];
+  };
+
+  /* Traverse the field tree and prepare some data that is used in later steps. */
+  FieldTreeInfo field_tree_info = preprocess_field_tree(fields_to_evaluate);
+
+  /* Get inputs that will be passed into the field when evaluated. */
+  Vector<const GVArray *> field_context_inputs = get_field_context_inputs(
+      scope, mask, context, field_tree_info.deduplicated_field_inputs);
+
+  /* Finish fields that output an input varray directly. For those we don't have to do any further
+   * processing. */
+  for (const int out_index : fields_to_evaluate.index_range()) {
+    const GFieldRef &field = fields_to_evaluate[out_index];
+    if (!field.node().is_input()) {
+      continue;
+    }
+    const FieldInput &field_input = static_cast<const FieldInput &>(field.node());
+    const int field_input_index = field_tree_info.deduplicated_field_inputs.index_of(field_input);
+    const GVArray *varray = field_context_inputs[field_input_index];
+    r_varrays[out_index] = varray;
+  }
+
+  Set<GFieldRef> varying_fields = find_varying_fields(field_tree_info, field_context_inputs);
+
+  /* Separate fields into two categories. Those that are constant and need to be evaluated only
+   * once, and those that need to be evaluated for every index. */
+  Vector<GFieldRef> varying_fields_to_evaluate;
+  Vector<int> varying_field_indices;
+  Vector<GFieldRef> constant_fields_to_evaluate;
+  Vector<int> constant_field_indices;
+  for (const int i : fields_to_evaluate.index_range()) {
+    if (r_varrays[i] != nullptr) {
+      /* Already done. */
+      continue;
+    }
+    GFieldRef field = fields_to_evaluate[i];
+    if (varying_fields.contains(field)) {
+      varying_fields_to_evaluate.append(field);
+      varying_field_indices.append(i);
+    }
+    else {
+      constant_fields_to_evaluate.append(field);
+      constant_field_indices.append(i);
+    }
+  }
+
+  /* Evaluate varying fields if necessary. */
+  if (!varying_fields_to_evaluate.is_empty()) {
+    /* Build the procedure for those fields. */
+    MFProcedure procedure;
+    build_multi_function_procedure_for_fields(
+        procedure, scope, field_tree_info, varying_fields_to_evaluate);
+    MFProcedureExecutor procedure_executor{"Procedure", procedure};
+    MFParamsBuilder mf_params{procedure_executor, array_size};
+    MFContextBuilder mf_context;
+
+    /* Provide inputs to the procedure executor. */
+    for (const GVArray *varray : field_context_inputs) {
+      mf_params.add_readonly_single_input(*varray);
+    }
+
+    for (const int i : varying_fields_to_evaluate.index_range()) {
+      const GFieldRef &field = varying_fields_to_evaluate[i];
+      const CPPType &type = field.cpp_type();
+      const int out_index = varying_field_indices[i];
+
+      /* Try to get an existing virtual array that the result should be written into. */
+      GVMutableArray *output_varray = get_dst_varray_if_available(out_index);
+      void *buffer;
+      if (output_varray == nullptr || !output_varray->is_span()) {
+        /* Allocate a new buffer for the computed result. */
+        buffer = scope.linear_allocator().allocate(type.size() * array_size, type.alignment());
+
+        /* Make sure that elements in the buffer will be destructed. */
+        PartiallyInitializedArray &destruct_helper = scope.construct<PartiallyInitializedArray>(
+            __func__);
+        destruct_helper.buffer = buffer;
+        destruct_helper.mask = mask;
+        destruct_helper.type = &type;
+
+        r_varrays[out_index] = &scope.construct<GVArray_For_GSpan>(
+            __func__, GSpan{type, buffer, array_size});
+      }
+      else {
+        /* Write the result into the existing span. */
+        buffer = output_varray->get_internal_span().data();
+
+        r_varrays[out_index] = output_varray;
+      }
+
+      /* Pass output buffer to the procedure executor. */
+      const GMutableSpan span{type, buffer, array_size};
+      mf_params.add_uninitialized_single_output(span);
+    }
+
+    procedure_executor.call(mask, mf_params, mf_context);
+  }
+
+  /* Evaluate constant fields if necessary. */
+  if (!constant_fields_to_evaluate.is_empty()) {
+    /* Build the procedure for those fields. */
+    MFProcedure procedure;
+    build_multi_function_procedure_for_fields(
+        procedure, scope, field_tree_info, constant_fields_to_evaluate);
+    MFProcedureExecutor procedure_executor{"Procedure", procedure};
+    MFParamsBuilder mf_params{procedure_executor, 1};
+    MFContextBuilder mf_context;
+
+    /* Provide inputs to the procedure executor. */
+    for (const GVArray *varray : field_context_inputs) {
+      mf_params.add_readonly_single_input(*varray);
+    }
+
+    for (const int i : constant_fields_to_evaluate.index_range()) {
+      const GFieldRef &field = constant_fields_to_evaluate[i];
+      const CPPType &type = field.cpp_type();
+      /* Allocate memory where the computed value will be stored in. */
+      void *buffer = scope.linear_allocator().allocate(type.size(), type.alignment());
+
+      /* Use this to make sure that the value is destructed in the end. */
+      PartiallyInitializedArray &destruct_helper = scope.construct<PartiallyInitializedArray>(
+          __func__);
+      destruct_helper.buffer = buffer;
+      destruct_helper.mask = IndexRange(1);
+      destruct_helper.type = &type;
+
+      /* Pass output buffer to the procedure executor. */
+      mf_params.add_uninitialized_single_output({type, buffer, 1});
+
+      /* Create virtual array that can be used after the procedure has been executed below. */
+      const int out_index = constant_field_indices[i];
+      r_varrays[out_index] = &scope.construct<GVArray_For_SingleValueRef>(
+          __func__, type, array_size, buffer);
+    }
+
+    procedure_executor.call(IndexRange(1), mf_params, mf_context);
+  }
+
+  /* Copy data to supplied destination arrays if necessary. In some cases the evaluation above has
+   * written the computed data in the right place already. */
+  if (!dst_varrays.is_empty()) {
+    for (const int out_index : fields_to_evaluate.index_range()) {
+      GVMutableArray *output_varray = get_dst_varray_if_available(out_index);
+      if (output_varray == nullptr) {
+        /* Caller did not provide a destination for this output. */
+        continue;
+      }
+      const GVArray *computed_varray = r_varrays[out_index];
+      BLI_assert(computed_varray->type() == output_varray->type());
+      if (output_varray == computed_varray) {
+        /* The result has been written into the destination provided by the caller already. */
+        continue;
+      }
+      /* Still have to copy over the data in the destination provided by the caller. */
+      if (output_varray->is_span()) {
+        /* Materialize into a span. */
+        computed_varray->materialize_to_uninitialized(output_varray->get_internal_span().data());
+      }
+      else {
+        /* Slower materialize into a different structure. */
+        const CPPType &type = computed_varray->type();
+        BUFFER_FOR_CPP_TYPE_VALUE(type, buffer);
+        for (const int i : mask) {
+          computed_varray->get_to_uninitialized(i, buffer);
+          output_varray->set_by_relocate(i, buffer);
+        }
+      }
+      r_varrays[out_index] = output_varray;
+    }
+  }
+  return r_varrays;
+}
+
+void evaluate_constant_field(const GField &field, void *r_value)
+{
+  ResourceScope scope;
+  FieldContext context;
+  Vector<const GVArray *> varrays = evaluate_fields(scope, {field}, IndexRange(1), context);
+  varrays[0]->get_to_uninitialized(0, r_value);
+}
+
+const GVArray *FieldContext::get_varray_for_input(const FieldInput &field_input,
+                                                  IndexMask mask,
+                                                  ResourceScope &scope) const
+{
+  /* By default ask the field input to create the varray. Another field context might overwrite
+   * the context here. */
+  return field_input.get_varray_for_context(*this, mask, scope);
+}
+
+/* --------------------------------------------------------------------
+ * FieldEvaluator.
+ */
+
+static Vector<int64_t> indices_from_selection(const VArray<bool> &selection)
+{
+  /* If the selection is just a single value, it's best to avoid calling this
+   * function when constructing an IndexMask and use an IndexRange instead. */
+  BLI_assert(!selection.is_single());
+
+  Vector<int64_t> indices;
+  if (selection.is_span()) {
+    Span<bool> span = selection.get_internal_span();
+    for (const int64_t i : span.index_range()) {
+      if (span[i]) {
+        indices.append(i);
+      }
+    }
+  }
+  else {
+    for (const int i : selection.index_range()) {
+      if (selection[i]) {
+        indices.append(i);
+      }
+    }
+  }
+  return indices;
+}
+
+int FieldEvaluator::add_with_destination(GField field, GVMutableArray &dst)
+{
+  const int field_index = fields_to_evaluate_.append_and_get_index(std::move(field));
+  dst_varrays_.append(&dst);
+  output_pointer_infos_.append({});
+  return field_index;
+}
+
+int FieldEvaluator::add_with_destination(GField field, GMutableSpan dst)
+{
+  GVMutableArray &varray = scope_.construct<GVMutableArray_For_GMutableSpan>(__func__, dst);
+  return this->add_with_destination(std::move(field), varray);
+}
+
+int FieldEvaluator::add(GField field, const GVArray **varray_ptr)
+{
+  const int field_index = fields_to_evaluate_.append_and_get_index(std::move(field));
+  dst_varrays_.append(nullptr);
+  output_pointer_infos_.append(OutputPointerInfo{
+      varray_ptr, [](void *dst, const GVArray &varray, ResourceScope &UNUSED(scope)) {
+        *(const GVArray **)dst = &varray;
+      }});
+  return field_index;
+}
+
+int FieldEvaluator::add(GField field)
+{
+  const int field_index = fields_to_evaluate_.append_and_get_index(std::move(field));
+  dst_varrays_.append(nullptr);
+  output_pointer_infos_.append({});
+  return field_index;
+}
+
+void FieldEvaluator::evaluate()
+{
+  BLI_assert_msg(!is_evaluated_, "Cannot evaluate fields twice.");
+  Array<GFieldRef> fields(fields_to_evaluate_.size());
+  for (const int i : fields_to_evaluate_.index_range()) {
+    fields[i] = fields_to_evaluate_[i];
+  }
+  evaluated_varrays_ = evaluate_fields(scope_, fields, mask_, context_, dst_varrays_);
+  BLI_assert(fields_to_evaluate_.size() == evaluated_varrays_.size());
+  for (const int i : fields_to_evaluate_.index_range()) {
+    OutputPointerInfo &info = output_pointer_infos_[i];
+    if (info.dst != nullptr) {
+      info.set(info.dst, *evaluated_varrays_[i], scope_);
+    }
+  }
+  is_evaluated_ = true;
+}
+
+IndexMask FieldEvaluator::get_evaluated_as_mask(const int field_index)
+{
+  const GVArray &varray = this->get_evaluated(field_index);
+  GVArray_Typed<bool> typed_varray{varray};
+
+  if (typed_varray->is_single()) {
+    if (typed_varray->get_internal_single()) {
+      return IndexRange(typed_varray.size());
+    }
+    return IndexRange(0);
+  }
+
+  return scope_.add_value(indices_from_selection(*typed_varray), __func__).as_span();
+}
+
+}  // namespace blender::fn

source/blender/functions/intern/multi_function_builder.cc

@@ -123,4 +123,32 @@ void CustomMF_DefaultOutput::call(IndexMask mask, MFParams params, MFContext UNU
   }
 }
 
+CustomMF_GenericCopy::CustomMF_GenericCopy(StringRef name, MFDataType data_type)
+{
+  MFSignatureBuilder signature{name};
+  signature.input("Input", data_type);
+  signature.output("Output", data_type);
+  signature_ = signature.build();
+  this->set_signature(&signature_);
+}
+
+void CustomMF_GenericCopy::call(IndexMask mask, MFParams params, MFContext UNUSED(context)) const
+{
+  const MFDataType data_type = this->param_type(0).data_type();
+  switch (data_type.category()) {
+    case MFDataType::Single: {
+      const GVArray &inputs = params.readonly_single_input(0, "Input");
+      GMutableSpan outputs = params.uninitialized_single_output(1, "Output");
+      inputs.materialize_to_uninitialized(mask, outputs.data());
+      break;
+    }
+    case MFDataType::Vector: {
+      const GVVectorArray &inputs = params.readonly_vector_input(0, "Input");
+      GVectorArray &outputs = params.vector_output(1, "Output");
+      outputs.extend(mask, inputs);
+      break;
+    }
+  }
+}
+
 }  // namespace blender::fn

source/blender/functions/intern/multi_function_procedure.cc

@@ -0,0 +1,794 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "FN_multi_function_procedure.hh"
+
+#include "BLI_dot_export.hh"
+#include "BLI_stack.hh"
+
+namespace blender::fn {
+
+void MFVariable::set_name(std::string name)
+{
+  name_ = std::move(name);
+}
+
+void MFCallInstruction::set_next(MFInstruction *instruction)
+{
+  if (next_ != nullptr) {
+    next_->prev_.remove_first_occurrence_and_reorder(this);
+  }
+  if (instruction != nullptr) {
+    instruction->prev_.append(this);
+  }
+  next_ = instruction;
+}
+
+void MFCallInstruction::set_param_variable(int param_index, MFVariable *variable)
+{
+  if (params_[param_index] != nullptr) {
+    params_[param_index]->users_.remove_first_occurrence_and_reorder(this);
+  }
+  if (variable != nullptr) {
+    BLI_assert(fn_->param_type(param_index).data_type() == variable->data_type());
+    variable->users_.append(this);
+  }
+  params_[param_index] = variable;
+}
+
+void MFCallInstruction::set_params(Span<MFVariable *> variables)
+{
+  BLI_assert(variables.size() == params_.size());
+  for (const int i : variables.index_range()) {
+    this->set_param_variable(i, variables[i]);
+  }
+}
+
+void MFBranchInstruction::set_condition(MFVariable *variable)
+{
+  if (condition_ != nullptr) {
+    condition_->users_.remove_first_occurrence_and_reorder(this);
+  }
+  if (variable != nullptr) {
+    variable->users_.append(this);
+  }
+  condition_ = variable;
+}
+
+void MFBranchInstruction::set_branch_true(MFInstruction *instruction)
+{
+  if (branch_true_ != nullptr) {
+    branch_true_->prev_.remove_first_occurrence_and_reorder(this);
+  }
+  if (instruction != nullptr) {
+    instruction->prev_.append(this);
+  }
+  branch_true_ = instruction;
+}
+
+void MFBranchInstruction::set_branch_false(MFInstruction *instruction)
+{
+  if (branch_false_ != nullptr) {
+    branch_false_->prev_.remove_first_occurrence_and_reorder(this);
+  }
+  if (instruction != nullptr) {
+    instruction->prev_.append(this);
+  }
+  branch_false_ = instruction;
+}
+
+void MFDestructInstruction::set_variable(MFVariable *variable)
+{
+  if (variable_ != nullptr) {
+    variable_->users_.remove_first_occurrence_and_reorder(this);
+  }
+  if (variable != nullptr) {
+    variable->users_.append(this);
+  }
+  variable_ = variable;
+}
+
+void MFDestructInstruction::set_next(MFInstruction *instruction)
+{
+  if (next_ != nullptr) {
+    next_->prev_.remove_first_occurrence_and_reorder(this);
+  }
+  if (instruction != nullptr) {
+    instruction->prev_.append(this);
+  }
+  next_ = instruction;
+}
+
+void MFDummyInstruction::set_next(MFInstruction *instruction)
+{
+  if (next_ != nullptr) {
+    next_->prev_.remove_first_occurrence_and_reorder(this);
+  }
+  if (instruction != nullptr) {
+    instruction->prev_.append(this);
+  }
+  next_ = instruction;
+}
+
+MFVariable &MFProcedure::new_variable(MFDataType data_type, std::string name)
+{
+  MFVariable &variable = *allocator_.construct<MFVariable>().release();
+  variable.name_ = std::move(name);
+  variable.data_type_ = data_type;
+  variable.id_ = variables_.size();
+  variables_.append(&variable);
+  return variable;
+}
+
+MFCallInstruction &MFProcedure::new_call_instruction(const MultiFunction &fn)
+{
+  MFCallInstruction &instruction = *allocator_.construct<MFCallInstruction>().release();
+  instruction.type_ = MFInstructionType::Call;
+  instruction.fn_ = &fn;
+  instruction.params_ = allocator_.allocate_array<MFVariable *>(fn.param_amount());
+  instruction.params_.fill(nullptr);
+  call_instructions_.append(&instruction);
+  return instruction;
+}
+
+MFBranchInstruction &MFProcedure::new_branch_instruction()
+{
+  MFBranchInstruction &instruction = *allocator_.construct<MFBranchInstruction>().release();
+  instruction.type_ = MFInstructionType::Branch;
+  branch_instructions_.append(&instruction);
+  return instruction;
+}
+
+MFDestructInstruction &MFProcedure::new_destruct_instruction()
+{
+  MFDestructInstruction &instruction = *allocator_.construct<MFDestructInstruction>().release();
+  instruction.type_ = MFInstructionType::Destruct;
+  destruct_instructions_.append(&instruction);
+  return instruction;
+}
+
+MFDummyInstruction &MFProcedure::new_dummy_instruction()
+{
+  MFDummyInstruction &instruction = *allocator_.construct<MFDummyInstruction>().release();
+  instruction.type_ = MFInstructionType::Dummy;
+  dummy_instructions_.append(&instruction);
+  return instruction;
+}
+
+MFReturnInstruction &MFProcedure::new_return_instruction()
+{
+  MFReturnInstruction &instruction = *allocator_.construct<MFReturnInstruction>().release();
+  instruction.type_ = MFInstructionType::Return;
+  return_instructions_.append(&instruction);
+  return instruction;
+}
+
+void MFProcedure::add_parameter(MFParamType::InterfaceType interface_type, MFVariable &variable)
+{
+  params_.append({interface_type, &variable});
+}
+
+void MFProcedure::set_entry(MFInstruction &entry)
+{
+  entry_ = &entry;
+}
+
+MFProcedure::~MFProcedure()
+{
+  for (MFCallInstruction *instruction : call_instructions_) {
+    instruction->~MFCallInstruction();
+  }
+  for (MFBranchInstruction *instruction : branch_instructions_) {
+    instruction->~MFBranchInstruction();
+  }
+  for (MFDestructInstruction *instruction : destruct_instructions_) {
+    instruction->~MFDestructInstruction();
+  }
+  for (MFDummyInstruction *instruction : dummy_instructions_) {
+    instruction->~MFDummyInstruction();
+  }
+  for (MFReturnInstruction *instruction : return_instructions_) {
+    instruction->~MFReturnInstruction();
+  }
+  for (MFVariable *variable : variables_) {
+    variable->~MFVariable();
+  }
+}
+
+bool MFProcedure::validate() const
+{
+  if (entry_ == nullptr) {
+    return false;
+  }
+  if (!this->validate_all_instruction_pointers_set()) {
+    return false;
+  }
+  if (!this->validate_all_params_provided()) {
+    return false;
+  }
+  if (!this->validate_same_variables_in_one_call()) {
+    return false;
+  }
+  if (!this->validate_parameters()) {
+    return false;
+  }
+  if (!this->validate_initialization()) {
+    return false;
+  }
+  return true;
+}
+
+bool MFProcedure::validate_all_instruction_pointers_set() const
+{
+  for (const MFCallInstruction *instruction : call_instructions_) {
+    if (instruction->next_ == nullptr) {
+      return false;
+    }
+  }
+  for (const MFDestructInstruction *instruction : destruct_instructions_) {
+    if (instruction->next_ == nullptr) {
+      return false;
+    }
+  }
+  for (const MFBranchInstruction *instruction : branch_instructions_) {
+    if (instruction->branch_true_ == nullptr) {
+      return false;
+    }
+    if (instruction->branch_false_ == nullptr) {
+      return false;
+    }
+  }
+  for (const MFDummyInstruction *instruction : dummy_instructions_) {
+    if (instruction->next_ == nullptr) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool MFProcedure::validate_all_params_provided() const
+{
+  for (const MFCallInstruction *instruction : call_instructions_) {
+    for (const MFVariable *variable : instruction->params_) {
+      if (variable == nullptr) {
+        return false;
+      }
+    }
+  }
+  for (const MFBranchInstruction *instruction : branch_instructions_) {
+    if (instruction->condition_ == nullptr) {
+      return false;
+    }
+  }
+  for (const MFDestructInstruction *instruction : destruct_instructions_) {
+    if (instruction->variable_ == nullptr) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool MFProcedure::validate_same_variables_in_one_call() const
+{
+  for (const MFCallInstruction *instruction : call_instructions_) {
+    const MultiFunction &fn = *instruction->fn_;
+    for (const int param_index : fn.param_indices()) {
+      const MFParamType param_type = fn.param_type(param_index);
+      const MFVariable *variable = instruction->params_[param_index];
+      for (const int other_param_index : fn.param_indices()) {
+        if (other_param_index == param_index) {
+          continue;
+        }
+        const MFVariable *other_variable = instruction->params_[other_param_index];
+        if (other_variable != variable) {
+          continue;
+        }
+        if (ELEM(param_type.interface_type(), MFParamType::Mutable, MFParamType::Output)) {
+          /* When a variable is used as mutable or output parameter, it can only be used once. */
+          return false;
+        }
+        const MFParamType other_param_type = fn.param_type(other_param_index);
+        /* A variable is allowed to be used as input more than once. */
+        if (other_param_type.interface_type() != MFParamType::Input) {
+          return false;
+        }
+      }
+    }
+  }
+  return true;
+}
+
+bool MFProcedure::validate_parameters() const
+{
+  Set<const MFVariable *> variables;
+  for (const MFParameter &param : params_) {
+    /* One variable cannot be used as multiple parameters. */
+    if (!variables.add(param.variable)) {
+      return false;
+    }
+  }
+  return true;
+}
+
+bool MFProcedure::validate_initialization() const
+{
+  /* TODO: Issue warning when it maybe wrongly initialized. */
+  for (const MFDestructInstruction *instruction : destruct_instructions_) {
+    const MFVariable &variable = *instruction->variable_;
+    const InitState state = this->find_initialization_state_before_instruction(*instruction,
+                                                                               variable);
+    if (!state.can_be_initialized) {
+      return false;
+    }
+  }
+  for (const MFBranchInstruction *instruction : branch_instructions_) {
+    const MFVariable &variable = *instruction->condition_;
+    const InitState state = this->find_initialization_state_before_instruction(*instruction,
+                                                                               variable);
+    if (!state.can_be_initialized) {
+      return false;
+    }
+  }
+  for (const MFCallInstruction *instruction : call_instructions_) {
+    const MultiFunction &fn = *instruction->fn_;
+    for (const int param_index : fn.param_indices()) {
+      const MFParamType param_type = fn.param_type(param_index);
+      const MFVariable &variable = *instruction->params_[param_index];
+      const InitState state = this->find_initialization_state_before_instruction(*instruction,
+                                                                                 variable);
+      switch (param_type.interface_type()) {
+        case MFParamType::Input:
+        case MFParamType::Mutable: {
+          if (!state.can_be_initialized) {
+            return false;
+          }
+          break;
+        }
+        case MFParamType::Output: {
+          if (!state.can_be_uninitialized) {
+            return false;
+          }
+          break;
+        }
+      }
+    }
+  }
+  Set<const MFVariable *> variables_that_should_be_initialized_on_return;
+  for (const MFParameter &param : params_) {
+    if (ELEM(param.type, MFParamType::Mutable, MFParamType::Output)) {
+      variables_that_should_be_initialized_on_return.add_new(param.variable);
+    }
+  }
+  for (const MFReturnInstruction *instruction : return_instructions_) {
+    for (const MFVariable *variable : variables_) {
+      const InitState init_state = this->find_initialization_state_before_instruction(*instruction,
+                                                                                      *variable);
+      if (variables_that_should_be_initialized_on_return.contains(variable)) {
+        if (!init_state.can_be_initialized) {
+          return false;
+        }
+      }
+      else {
+        if (!init_state.can_be_uninitialized) {
+          return false;
+        }
+      }
+    }
+  }
+  return true;
+}
+
+MFProcedure::InitState MFProcedure::find_initialization_state_before_instruction(
+    const MFInstruction &target_instruction, const MFVariable &target_variable) const
+{
+  InitState state;
+
+  auto check_entry_instruction = [&]() {
+    bool caller_initialized_variable = false;
+    for (const MFParameter &param : params_) {
+      if (param.variable == &target_variable) {
+        if (ELEM(param.type, MFParamType::Input, MFParamType::Mutable)) {
+          caller_initialized_variable = true;
+          break;
+        }
+      }
+    }
+    if (caller_initialized_variable) {
+      state.can_be_initialized = true;
+    }
+    else {
+      state.can_be_uninitialized = true;
+    }
+  };
+
+  if (&target_instruction == entry_) {
+    check_entry_instruction();
+  }
+
+  Set<const MFInstruction *> checked_instructions;
+  Stack<const MFInstruction *> instructions_to_check;
+  instructions_to_check.push_multiple(target_instruction.prev_);
+
+  while (!instructions_to_check.is_empty()) {
+    const MFInstruction &instruction = *instructions_to_check.pop();
+    if (!checked_instructions.add(&instruction)) {
+      /* Skip if the instruction has been checked already. */
+      continue;
+    }
+    bool state_modified = false;
+    switch (instruction.type_) {
+      case MFInstructionType::Call: {
+        const MFCallInstruction &call_instruction = static_cast<const MFCallInstruction &>(
+            instruction);
+        const MultiFunction &fn = *call_instruction.fn_;
+        for (const int param_index : fn.param_indices()) {
+          if (call_instruction.params_[param_index] == &target_variable) {
+            const MFParamType param_type = fn.param_type(param_index);
+            if (param_type.interface_type() == MFParamType::Output) {
+              state.can_be_initialized = true;
+              state_modified = true;
+              break;
+            }
+          }
+        }
+        break;
+      }
+      case MFInstructionType::Destruct: {
+        const MFDestructInstruction &destruct_instruction =
+            static_cast<const MFDestructInstruction &>(instruction);
+        if (destruct_instruction.variable_ == &target_variable) {
+          state.can_be_uninitialized = true;
+          state_modified = true;
+        }
+        break;
+      }
+      case MFInstructionType::Branch:
+      case MFInstructionType::Dummy:
+      case MFInstructionType::Return: {
+        /* These instruction types don't change the initialization state of variables. */
+        break;
+      }
+    }
+
+    if (!state_modified) {
+      if (&instruction == entry_) {
+        check_entry_instruction();
+      }
+      instructions_to_check.push_multiple(instruction.prev_);
+    }
+  }
+
+  return state;
+}
+
+class MFProcedureDotExport {
+ private:
+  const MFProcedure &procedure_;
+  dot::DirectedGraph digraph_;
+  Map<const MFInstruction *, dot::Node *> dot_nodes_by_begin_;
+  Map<const MFInstruction *, dot::Node *> dot_nodes_by_end_;
+
+ public:
+  MFProcedureDotExport(const MFProcedure &procedure) : procedure_(procedure)
+  {
+  }
+
+  std::string generate()
+  {
+    this->create_nodes();
+    this->create_edges();
+    return digraph_.to_dot_string();
+  }
+
+  void create_nodes()
+  {
+    Vector<const MFInstruction *> all_instructions;
+    auto add_instructions = [&](auto instructions) {
+      all_instructions.extend(instructions.begin(), instructions.end());
+    };
+    add_instructions(procedure_.call_instructions_);
+    add_instructions(procedure_.branch_instructions_);
+    add_instructions(procedure_.destruct_instructions_);
+    add_instructions(procedure_.dummy_instructions_);
+    add_instructions(procedure_.return_instructions_);
+
+    Set<const MFInstruction *> handled_instructions;
+
+    for (const MFInstruction *representative : all_instructions) {
+      if (handled_instructions.contains(representative)) {
+        continue;
+      }
+      Vector<const MFInstruction *> block_instructions = this->get_instructions_in_block(
+          *representative);
+      std::stringstream ss;
+      ss << "<";
+
+      for (const MFInstruction *current : block_instructions) {
+        handled_instructions.add_new(current);
+        switch (current->type()) {
+          case MFInstructionType::Call: {
+            this->instruction_to_string(*static_cast<const MFCallInstruction *>(current), ss);
+            break;
+          }
+          case MFInstructionType::Destruct: {
+            this->instruction_to_string(*static_cast<const MFDestructInstruction *>(current), ss);
+            break;
+          }
+          case MFInstructionType::Dummy: {
+            this->instruction_to_string(*static_cast<const MFDummyInstruction *>(current), ss);
+            break;
+          }
+          case MFInstructionType::Return: {
+            this->instruction_to_string(*static_cast<const MFReturnInstruction *>(current), ss);
+            break;
+          }
+          case MFInstructionType::Branch: {
+            this->instruction_to_string(*static_cast<const MFBranchInstruction *>(current), ss);
+            break;
+          }
+        }
+        ss << R"(<br align="left" />)";
+      }
+      ss << ">";
+
+      dot::Node &dot_node = digraph_.new_node(ss.str());
+      dot_node.set_shape(dot::Attr_shape::Rectangle);
+      dot_nodes_by_begin_.add_new(block_instructions.first(), &dot_node);
+      dot_nodes_by_end_.add_new(block_instructions.last(), &dot_node);
+    }
+  }
+
+  void create_edges()
+  {
+    auto create_edge = [&](dot::Node &from_node,
+                           const MFInstruction *to_instruction) -> dot::DirectedEdge & {
+      if (to_instruction == nullptr) {
+        dot::Node &to_node = digraph_.new_node("missing");
+        to_node.set_shape(dot::Attr_shape::Diamond);
+        return digraph_.new_edge(from_node, to_node);
+      }
+      dot::Node &to_node = *dot_nodes_by_begin_.lookup(to_instruction);
+      return digraph_.new_edge(from_node, to_node);
+    };
+
+    for (auto item : dot_nodes_by_end_.items()) {
+      const MFInstruction &from_instruction = *item.key;
+      dot::Node &from_node = *item.value;
+      switch (from_instruction.type()) {
+        case MFInstructionType::Call: {
+          const MFInstruction *to_instruction =
+              static_cast<const MFCallInstruction &>(from_instruction).next();
+          create_edge(from_node, to_instruction);
+          break;
+        }
+        case MFInstructionType::Destruct: {
+          const MFInstruction *to_instruction =
+              static_cast<const MFDestructInstruction &>(from_instruction).next();
+          create_edge(from_node, to_instruction);
+          break;
+        }
+        case MFInstructionType::Dummy: {
+          const MFInstruction *to_instruction =
+              static_cast<const MFDummyInstruction &>(from_instruction).next();
+          create_edge(from_node, to_instruction);
+          break;
+        }
+        case MFInstructionType::Return: {
+          break;
+        }
+        case MFInstructionType::Branch: {
+          const MFBranchInstruction &branch_instruction = static_cast<const MFBranchInstruction &>(
+              from_instruction);
+          const MFInstruction *to_true_instruction = branch_instruction.branch_true();
+          const MFInstruction *to_false_instruction = branch_instruction.branch_false();
+          create_edge(from_node, to_true_instruction).attributes.set("color", "#118811");
+          create_edge(from_node, to_false_instruction).attributes.set("color", "#881111");
+          break;
+        }
+      }
+    }
+
+    dot::Node &entry_node = this->create_entry_node();
+    create_edge(entry_node, procedure_.entry());
+  }
+
+  bool has_to_be_block_begin(const MFInstruction &instruction)
+  {
+    if (procedure_.entry() == &instruction) {
+      return true;
+    }
+    if (instruction.prev().size() != 1) {
+      return true;
+    }
+    if (instruction.prev()[0]->type() == MFInstructionType::Branch) {
+      return true;
+    }
+    return false;
+  }
+
+  const MFInstruction &get_first_instruction_in_block(const MFInstruction &representative)
+  {
+    const MFInstruction *current = &representative;
+    while (!this->has_to_be_block_begin(*current)) {
+      current = current->prev()[0];
+      if (current == &representative) {
+        /* There is a loop without entry or exit, just break it up here. */
+        break;
+      }
+    }
+    return *current;
+  }
+
+  const MFInstruction *get_next_instruction_in_block(const MFInstruction &instruction,
+                                                     const MFInstruction &block_begin)
+  {
+    const MFInstruction *next = nullptr;
+    switch (instruction.type()) {
+      case MFInstructionType::Call: {
+        next = static_cast<const MFCallInstruction &>(instruction).next();
+        break;
+      }
+      case MFInstructionType::Destruct: {
+        next = static_cast<const MFDestructInstruction &>(instruction).next();
+        break;
+      }
+      case MFInstructionType::Dummy: {
+        next = static_cast<const MFDummyInstruction &>(instruction).next();
+        break;
+      }
+      case MFInstructionType::Return:
+      case MFInstructionType::Branch: {
+        break;
+      }
+    }
+    if (next == nullptr) {
+      return nullptr;
+    }
+    if (next == &block_begin) {
+      return nullptr;
+    }
+    if (this->has_to_be_block_begin(*next)) {
+      return nullptr;
+    }
+    return next;
+  }
+
+  Vector<const MFInstruction *> get_instructions_in_block(const MFInstruction &representative)
+  {
+    Vector<const MFInstruction *> instructions;
+    const MFInstruction &begin = this->get_first_instruction_in_block(representative);
+    for (const MFInstruction *current = &begin; current != nullptr;
+         current = this->get_next_instruction_in_block(*current, begin)) {
+      instructions.append(current);
+    }
+    return instructions;
+  }
+
+  void variable_to_string(const MFVariable *variable, std::stringstream &ss)
+  {
+    if (variable == nullptr) {
+      ss << "null";
+    }
+    else {
+      ss << "$" << variable->id();
+      if (!variable->name().is_empty()) {
+        ss << "(" << variable->name() << ")";
+      }
+    }
+  }
+
+  void instruction_name_format(StringRef name, std::stringstream &ss)
+  {
+    ss << name;
+  }
+
+  void instruction_to_string(const MFCallInstruction &instruction, std::stringstream &ss)
+  {
+    const MultiFunction &fn = instruction.fn();
+    this->instruction_name_format(fn.name() + ": ", ss);
+    for (const int param_index : fn.param_indices()) {
+      const MFParamType param_type = fn.param_type(param_index);
+      const MFVariable *variable = instruction.params()[param_index];
+      ss << R"(<font color="grey30">)";
+      switch (param_type.interface_type()) {
+        case MFParamType::Input: {
+          ss << "in";
+          break;
+        }
+        case MFParamType::Mutable: {
+          ss << "mut";
+          break;
+        }
+        case MFParamType::Output: {
+          ss << "out";
+          break;
+        }
+      }
+      ss << " </font> ";
+      variable_to_string(variable, ss);
+      if (param_index < fn.param_amount() - 1) {
+        ss << ", ";
+      }
+    }
+  }
+
+  void instruction_to_string(const MFDestructInstruction &instruction, std::stringstream &ss)
+  {
+    instruction_name_format("Destruct ", ss);
+    variable_to_string(instruction.variable(), ss);
+  }
+
+  void instruction_to_string(const MFDummyInstruction &UNUSED(instruction), std::stringstream &ss)
+  {
+    instruction_name_format("Dummy ", ss);
+  }
+
+  void instruction_to_string(const MFReturnInstruction &UNUSED(instruction), std::stringstream &ss)
+  {
+    instruction_name_format("Return ", ss);
+
+    Vector<ConstMFParameter> outgoing_parameters;
+    for (const ConstMFParameter &param : procedure_.params()) {
+      if (ELEM(param.type, MFParamType::Mutable, MFParamType::Output)) {
+        outgoing_parameters.append(param);
+      }
+    }
+    for (const int param_index : outgoing_parameters.index_range()) {
+      const ConstMFParameter &param = outgoing_parameters[param_index];
+      variable_to_string(param.variable, ss);
+      if (param_index < outgoing_parameters.size() - 1) {
+        ss << ", ";
+      }
+    }
+  }
+
+  void instruction_to_string(const MFBranchInstruction &instruction, std::stringstream &ss)
+  {
+    instruction_name_format("Branch ", ss);
+    variable_to_string(instruction.condition(), ss);
+  }
+
+  dot::Node &create_entry_node()
+  {
+    std::stringstream ss;
+    ss << "Entry: ";
+    Vector<ConstMFParameter> incoming_parameters;
+    for (const ConstMFParameter &param : procedure_.params()) {
+      if (ELEM(param.type, MFParamType::Input, MFParamType::Mutable)) {
+        incoming_parameters.append(param);
+      }
+    }
+    for (const int param_index : incoming_parameters.index_range()) {
+      const ConstMFParameter &param = incoming_parameters[param_index];
+      variable_to_string(param.variable, ss);
+      if (param_index < incoming_parameters.size() - 1) {
+        ss << ", ";
+      }
+    }
+
+    dot::Node &node = digraph_.new_node(ss.str());
+    node.set_shape(dot::Attr_shape::Ellipse);
+    return node;
+  }
+};
+
+std::string MFProcedure::to_dot() const
+{
+  MFProcedureDotExport dot_export{*this};
+  return dot_export.generate();
+}
+
+}  // namespace blender::fn

source/blender/functions/intern/multi_function_procedure_builder.cc

@@ -0,0 +1,175 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "FN_multi_function_procedure_builder.hh"
+
+namespace blender::fn {
+
+void MFInstructionCursor::insert(MFProcedure &procedure, MFInstruction *new_instruction)
+{
+  if (instruction_ == nullptr) {
+    if (is_entry_) {
+      procedure.set_entry(*new_instruction);
+    }
+    else {
+      /* The cursors points at nothing, nothing to do. */
+    }
+  }
+  else {
+    switch (instruction_->type()) {
+      case MFInstructionType::Call: {
+        static_cast<MFCallInstruction *>(instruction_)->set_next(new_instruction);
+        break;
+      }
+      case MFInstructionType::Branch: {
+        MFBranchInstruction &branch_instruction = *static_cast<MFBranchInstruction *>(
+            instruction_);
+        if (branch_output_) {
+          branch_instruction.set_branch_true(new_instruction);
+        }
+        else {
+          branch_instruction.set_branch_false(new_instruction);
+        }
+        break;
+      }
+      case MFInstructionType::Destruct: {
+        static_cast<MFDestructInstruction *>(instruction_)->set_next(new_instruction);
+        break;
+      }
+      case MFInstructionType::Dummy: {
+        static_cast<MFDummyInstruction *>(instruction_)->set_next(new_instruction);
+        break;
+      }
+      case MFInstructionType::Return: {
+        /* It shouldn't be possible to build a cursor that points to a return instruction. */
+        BLI_assert_unreachable();
+        break;
+      }
+    }
+  }
+}
+
+void MFProcedureBuilder::add_destruct(MFVariable &variable)
+{
+  MFDestructInstruction &instruction = procedure_->new_destruct_instruction();
+  instruction.set_variable(&variable);
+  this->link_to_cursors(&instruction);
+  cursors_ = {MFInstructionCursor{instruction}};
+}
+
+void MFProcedureBuilder::add_destruct(Span<MFVariable *> variables)
+{
+  for (MFVariable *variable : variables) {
+    this->add_destruct(*variable);
+  }
+}
+
+MFReturnInstruction &MFProcedureBuilder::add_return()
+{
+  MFReturnInstruction &instruction = procedure_->new_return_instruction();
+  this->link_to_cursors(&instruction);
+  cursors_ = {};
+  return instruction;
+}
+
+MFCallInstruction &MFProcedureBuilder::add_call_with_no_variables(const MultiFunction &fn)
+{
+  MFCallInstruction &instruction = procedure_->new_call_instruction(fn);
+  this->link_to_cursors(&instruction);
+  cursors_ = {MFInstructionCursor{instruction}};
+  return instruction;
+}
+
+MFCallInstruction &MFProcedureBuilder::add_call_with_all_variables(
+    const MultiFunction &fn, Span<MFVariable *> param_variables)
+{
+  MFCallInstruction &instruction = this->add_call_with_no_variables(fn);
+  instruction.set_params(param_variables);
+  return instruction;
+}
+
+Vector<MFVariable *> MFProcedureBuilder::add_call(const MultiFunction &fn,
+                                                  Span<MFVariable *> input_and_mutable_variables)
+{
+  Vector<MFVariable *> output_variables;
+  MFCallInstruction &instruction = this->add_call_with_no_variables(fn);
+  for (const int param_index : fn.param_indices()) {
+    const MFParamType param_type = fn.param_type(param_index);
+    switch (param_type.interface_type()) {
+      case MFParamType::Input:
+      case MFParamType::Mutable: {
+        MFVariable *variable = input_and_mutable_variables.first();
+        instruction.set_param_variable(param_index, variable);
+        input_and_mutable_variables = input_and_mutable_variables.drop_front(1);
+        break;
+      }
+      case MFParamType::Output: {
+        MFVariable &variable = procedure_->new_variable(param_type.data_type(),
+                                                        fn.param_name(param_index));
+        instruction.set_param_variable(param_index, &variable);
+        output_variables.append(&variable);
+        break;
+      }
+    }
+  }
+  /* All passed in variables should have been dropped in the loop above. */
+  BLI_assert(input_and_mutable_variables.is_empty());
+  return output_variables;
+}
+
+MFProcedureBuilder::Branch MFProcedureBuilder::add_branch(MFVariable &condition)
+{
+  MFBranchInstruction &instruction = procedure_->new_branch_instruction();
+  instruction.set_condition(&condition);
+  this->link_to_cursors(&instruction);
+  /* Clear cursors because this builder ends here. */
+  cursors_.clear();
+
+  Branch branch{*procedure_, *procedure_};
+  branch.branch_true.set_cursor(MFInstructionCursor{instruction, true});
+  branch.branch_false.set_cursor(MFInstructionCursor{instruction, false});
+  return branch;
+}
+
+MFProcedureBuilder::Loop MFProcedureBuilder::add_loop()
+{
+  MFDummyInstruction &loop_begin = procedure_->new_dummy_instruction();
+  MFDummyInstruction &loop_end = procedure_->new_dummy_instruction();
+  this->link_to_cursors(&loop_begin);
+  cursors_ = {MFInstructionCursor{loop_begin}};
+
+  Loop loop;
+  loop.begin = &loop_begin;
+  loop.end = &loop_end;
+
+  return loop;
+}
+
+void MFProcedureBuilder::add_loop_continue(Loop &loop)
+{
+  this->link_to_cursors(loop.begin);
+  /* Clear cursors because this builder ends here. */
+  cursors_.clear();
+}
+
+void MFProcedureBuilder::add_loop_break(Loop &loop)
+{
+  this->link_to_cursors(loop.end);
+  /* Clear cursors because this builder ends here. */
+  cursors_.clear();
+}
+
+}  // namespace blender::fn

source/blender/functions/tests/FN_field_test.cc

@@ -0,0 +1,278 @@
+/* Apache License, Version 2.0 */
+
+#include "testing/testing.h"
+
+#include "FN_cpp_type.hh"
+#include "FN_field.hh"
+#include "FN_multi_function_builder.hh"
+
+namespace blender::fn::tests {
+
+TEST(field, ConstantFunction)
+{
+  /* TODO: Figure out how to not use another "FieldOperation(" inside of std::make_shared. */
+  GField constant_field{std::make_shared<FieldOperation>(
+                            FieldOperation(std::make_unique<CustomMF_Constant<int>>(10), {})),
+                        0};
+
+  Array<int> result(4);
+
+  FieldContext context;
+  FieldEvaluator evaluator{context, 4};
+  evaluator.add_with_destination(constant_field, result.as_mutable_span());
+  evaluator.evaluate();
+  EXPECT_EQ(result[0], 10);
+  EXPECT_EQ(result[1], 10);
+  EXPECT_EQ(result[2], 10);
+  EXPECT_EQ(result[3], 10);
+}
+
+class IndexFieldInput final : public FieldInput {
+ public:
+  IndexFieldInput() : FieldInput(CPPType::get<int>(), "Index")
+  {
+  }
+
+  const GVArray *get_varray_for_context(const FieldContext &UNUSED(context),
+                                        IndexMask mask,
+                                        ResourceScope &scope) const final
+  {
+    auto index_func = [](int i) { return i; };
+    return &scope.construct<
+        GVArray_For_EmbeddedVArray<int, VArray_For_Func<int, decltype(index_func)>>>(
+        __func__, mask.min_array_size(), mask.min_array_size(), index_func);
+  }
+};
+
+TEST(field, VArrayInput)
+{
+  GField index_field{std::make_shared<IndexFieldInput>()};
+
+  Array<int> result_1(4);
+
+  FieldContext context;
+  FieldEvaluator evaluator{context, 4};
+  evaluator.add_with_destination(index_field, result_1.as_mutable_span());
+  evaluator.evaluate();
+  EXPECT_EQ(result_1[0], 0);
+  EXPECT_EQ(result_1[1], 1);
+  EXPECT_EQ(result_1[2], 2);
+  EXPECT_EQ(result_1[3], 3);
+
+  /* Evaluate a second time, just to test that the first didn't break anything. */
+  Array<int> result_2(10);
+
+  const Array<int64_t> indices = {2, 4, 6, 8};
+  const IndexMask mask{indices};
+
+  FieldEvaluator evaluator_2{context, &mask};
+  evaluator_2.add_with_destination(index_field, result_2.as_mutable_span());
+  evaluator_2.evaluate();
+  EXPECT_EQ(result_2[2], 2);
+  EXPECT_EQ(result_2[4], 4);
+  EXPECT_EQ(result_2[6], 6);
+  EXPECT_EQ(result_2[8], 8);
+}
+
+TEST(field, VArrayInputMultipleOutputs)
+{
+  std::shared_ptr<FieldInput> index_input = std::make_shared<IndexFieldInput>();
+  GField field_1{index_input};
+  GField field_2{index_input};
+
+  Array<int> result_1(10);
+  Array<int> result_2(10);
+
+  const Array<int64_t> indices = {2, 4, 6, 8};
+  const IndexMask mask{indices};
+
+  FieldContext context;
+  FieldEvaluator evaluator{context, &mask};
+  evaluator.add_with_destination(field_1, result_1.as_mutable_span());
+  evaluator.add_with_destination(field_2, result_2.as_mutable_span());
+  evaluator.evaluate();
+  EXPECT_EQ(result_1[2], 2);
+  EXPECT_EQ(result_1[4], 4);
+  EXPECT_EQ(result_1[6], 6);
+  EXPECT_EQ(result_1[8], 8);
+  EXPECT_EQ(result_2[2], 2);
+  EXPECT_EQ(result_2[4], 4);
+  EXPECT_EQ(result_2[6], 6);
+  EXPECT_EQ(result_2[8], 8);
+}
+
+TEST(field, InputAndFunction)
+{
+  GField index_field{std::make_shared<IndexFieldInput>()};
+
+  std::unique_ptr<MultiFunction> add_fn = std::make_unique<CustomMF_SI_SI_SO<int, int, int>>(
+      "add", [](int a, int b) { return a + b; });
+  GField output_field{std::make_shared<FieldOperation>(
+                          FieldOperation(std::move(add_fn), {index_field, index_field})),
+                      0};
+
+  Array<int> result(10);
+
+  const Array<int64_t> indices = {2, 4, 6, 8};
+  const IndexMask mask{indices};
+
+  FieldContext context;
+  FieldEvaluator evaluator{context, &mask};
+  evaluator.add_with_destination(output_field, result.as_mutable_span());
+  evaluator.evaluate();
+  EXPECT_EQ(result[2], 4);
+  EXPECT_EQ(result[4], 8);
+  EXPECT_EQ(result[6], 12);
+  EXPECT_EQ(result[8], 16);
+}
+
+TEST(field, TwoFunctions)
+{
+  GField index_field{std::make_shared<IndexFieldInput>()};
+
+  std::unique_ptr<MultiFunction> add_fn = std::make_unique<CustomMF_SI_SI_SO<int, int, int>>(
+      "add", [](int a, int b) { return a + b; });
+  GField add_field{std::make_shared<FieldOperation>(
+                       FieldOperation(std::move(add_fn), {index_field, index_field})),
+                   0};
+
+  std::unique_ptr<MultiFunction> add_10_fn = std::make_unique<CustomMF_SI_SO<int, int>>(
+      "add_10", [](int a) { return a + 10; });
+  GField result_field{
+      std::make_shared<FieldOperation>(FieldOperation(std::move(add_10_fn), {add_field})), 0};
+
+  Array<int> result(10);
+
+  const Array<int64_t> indices = {2, 4, 6, 8};
+  const IndexMask mask{indices};
+
+  FieldContext context;
+  FieldEvaluator evaluator{context, &mask};
+  evaluator.add_with_destination(result_field, result.as_mutable_span());
+  evaluator.evaluate();
+  EXPECT_EQ(result[2], 14);
+  EXPECT_EQ(result[4], 18);
+  EXPECT_EQ(result[6], 22);
+  EXPECT_EQ(result[8], 26);
+}
+
+class TwoOutputFunction : public MultiFunction {
+ private:
+  MFSignature signature_;
+
+ public:
+  TwoOutputFunction(StringRef name)
+  {
+    MFSignatureBuilder signature{name};
+    signature.single_input<int>("In1");
+    signature.single_input<int>("In2");
+    signature.single_output<int>("Add");
+    signature.single_output<int>("Add10");
+    signature_ = signature.build();
+    this->set_signature(&signature_);
+  }
+
+  void call(IndexMask mask, MFParams params, MFContext UNUSED(context)) const override
+  {
+    const VArray<int> &in1 = params.readonly_single_input<int>(0, "In1");
+    const VArray<int> &in2 = params.readonly_single_input<int>(1, "In2");
+    MutableSpan<int> add = params.uninitialized_single_output<int>(2, "Add");
+    MutableSpan<int> add_10 = params.uninitialized_single_output<int>(3, "Add10");
+    mask.foreach_index([&](const int64_t i) {
+      add[i] = in1[i] + in2[i];
+      add_10[i] = add[i] + 10;
+    });
+  }
+};
+
+TEST(field, FunctionTwoOutputs)
+{
+  /* Also use two separate input fields, why not. */
+  GField index_field_1{std::make_shared<IndexFieldInput>()};
+  GField index_field_2{std::make_shared<IndexFieldInput>()};
+
+  std::shared_ptr<FieldOperation> fn = std::make_shared<FieldOperation>(FieldOperation(
+      std::make_unique<TwoOutputFunction>("SI_SI_SO_SO"), {index_field_1, index_field_2}));
+
+  GField result_field_1{fn, 0};
+  GField result_field_2{fn, 1};
+
+  Array<int> result_1(10);
+  Array<int> result_2(10);
+
+  const Array<int64_t> indices = {2, 4, 6, 8};
+  const IndexMask mask{indices};
+
+  FieldContext context;
+  FieldEvaluator evaluator{context, &mask};
+  evaluator.add_with_destination(result_field_1, result_1.as_mutable_span());
+  evaluator.add_with_destination(result_field_2, result_2.as_mutable_span());
+  evaluator.evaluate();
+  EXPECT_EQ(result_1[2], 4);
+  EXPECT_EQ(result_1[4], 8);
+  EXPECT_EQ(result_1[6], 12);
+  EXPECT_EQ(result_1[8], 16);
+  EXPECT_EQ(result_2[2], 14);
+  EXPECT_EQ(result_2[4], 18);
+  EXPECT_EQ(result_2[6], 22);
+  EXPECT_EQ(result_2[8], 26);
+}
+
+TEST(field, TwoFunctionsTwoOutputs)
+{
+  GField index_field{std::make_shared<IndexFieldInput>()};
+
+  std::shared_ptr<FieldOperation> fn = std::make_shared<FieldOperation>(FieldOperation(
+      std::make_unique<TwoOutputFunction>("SI_SI_SO_SO"), {index_field, index_field}));
+
+  Array<int64_t> mask_indices = {2, 4, 6, 8};
+  IndexMask mask = mask_indices.as_span();
+
+  Field<int> result_field_1{fn, 0};
+  Field<int> intermediate_field{fn, 1};
+
+  std::unique_ptr<MultiFunction> add_10_fn = std::make_unique<CustomMF_SI_SO<int, int>>(
+      "add_10", [](int a) { return a + 10; });
+  Field<int> result_field_2{
+      std::make_shared<FieldOperation>(FieldOperation(std::move(add_10_fn), {intermediate_field})),
+      0};
+
+  FieldContext field_context;
+  FieldEvaluator field_evaluator{field_context, &mask};
+  const VArray<int> *result_1 = nullptr;
+  const VArray<int> *result_2 = nullptr;
+  field_evaluator.add(result_field_1, &result_1);
+  field_evaluator.add(result_field_2, &result_2);
+  field_evaluator.evaluate();
+
+  EXPECT_EQ(result_1->get(2), 4);
+  EXPECT_EQ(result_1->get(4), 8);
+  EXPECT_EQ(result_1->get(6), 12);
+  EXPECT_EQ(result_1->get(8), 16);
+  EXPECT_EQ(result_2->get(2), 24);
+  EXPECT_EQ(result_2->get(4), 28);
+  EXPECT_EQ(result_2->get(6), 32);
+  EXPECT_EQ(result_2->get(8), 36);
+}
+
+TEST(field, SameFieldTwice)
+{
+  GField constant_field{
+      std::make_shared<FieldOperation>(std::make_unique<CustomMF_Constant<int>>(10)), 0};
+
+  FieldContext field_context;
+  IndexMask mask{IndexRange(2)};
+  ResourceScope scope;
+  Vector<const GVArray *> results = evaluate_fields(
+      scope, {constant_field, constant_field}, mask, field_context);
+
+  GVArray_Typed<int> varray1{*results[0]};
+  GVArray_Typed<int> varray2{*results[1]};
+
+  EXPECT_EQ(varray1->get(0), 10);
+  EXPECT_EQ(varray1->get(1), 10);
+  EXPECT_EQ(varray2->get(0), 10);
+  EXPECT_EQ(varray2->get(1), 10);
+}
+
+}  // namespace blender::fn::tests

source/blender/functions/tests/FN_multi_function_procedure_test.cc

@@ -0,0 +1,344 @@
+/* Apache License, Version 2.0 */
+
+#include "testing/testing.h"
+
+#include "FN_multi_function_builder.hh"
+#include "FN_multi_function_procedure_builder.hh"
+#include "FN_multi_function_procedure_executor.hh"
+#include "FN_multi_function_test_common.hh"
+
+namespace blender::fn::tests {
+
+TEST(multi_function_procedure, SimpleTest)
+{
+  /**
+   * procedure(int var1, int var2, int *var4) {
+   *   int var3 = var1 + var2;
+   *   var4 = var2 + var3;
+   *   var4 += 10;
+   * }
+   */
+
+  CustomMF_SI_SI_SO<int, int, int> add_fn{"add", [](int a, int b) { return a + b; }};
+  CustomMF_SM<int> add_10_fn{"add_10", [](int &a) { a += 10; }};
+
+  MFProcedure procedure;
+  MFProcedureBuilder builder{procedure};
+
+  MFVariable *var1 = &builder.add_single_input_parameter<int>();
+  MFVariable *var2 = &builder.add_single_input_parameter<int>();
+  auto [var3] = builder.add_call<1>(add_fn, {var1, var2});
+  auto [var4] = builder.add_call<1>(add_fn, {var2, var3});
+  builder.add_call(add_10_fn, {var4});
+  builder.add_destruct({var1, var2, var3});
+  builder.add_return();
+  builder.add_output_parameter(*var4);
+
+  EXPECT_TRUE(procedure.validate());
+
+  MFProcedureExecutor executor{"My Procedure", procedure};
+
+  MFParamsBuilder params{executor, 3};
+  MFContextBuilder context;
+
+  Array<int> input_array = {1, 2, 3};
+  params.add_readonly_single_input(input_array.as_span());
+  params.add_readonly_single_input_value(3);
+
+  Array<int> output_array(3);
+  params.add_uninitialized_single_output(output_array.as_mutable_span());
+
+  executor.call(IndexRange(3), params, context);
+
+  EXPECT_EQ(output_array[0], 17);
+  EXPECT_EQ(output_array[1], 18);
+  EXPECT_EQ(output_array[2], 19);
+}
+
+TEST(multi_function_procedure, BranchTest)
+{
+  /**
+   * procedure(int &var1, bool var2) {
+   *   if (var2) {
+   *     var1 += 100;
+   *   }
+   *   else {
+   *     var1 += 10;
+   *   }
+   *   var1 += 10;
+   * }
+   */
+
+  CustomMF_SM<int> add_10_fn{"add_10", [](int &a) { a += 10; }};
+  CustomMF_SM<int> add_100_fn{"add_100", [](int &a) { a += 100; }};
+
+  MFProcedure procedure;
+  MFProcedureBuilder builder{procedure};
+
+  MFVariable *var1 = &builder.add_single_mutable_parameter<int>();
+  MFVariable *var2 = &builder.add_single_input_parameter<bool>();
+
+  MFProcedureBuilder::Branch branch = builder.add_branch(*var2);
+  branch.branch_false.add_call(add_10_fn, {var1});
+  branch.branch_true.add_call(add_100_fn, {var1});
+  builder.set_cursor_after_branch(branch);
+  builder.add_call(add_10_fn, {var1});
+  builder.add_destruct({var2});
+  builder.add_return();
+
+  EXPECT_TRUE(procedure.validate());
+
+  MFProcedureExecutor procedure_fn{"Condition Test", procedure};
+  MFParamsBuilder params(procedure_fn, 5);
+
+  Array<int> values_a = {1, 5, 3, 6, 2};
+  Array<bool> values_cond = {true, false, true, true, false};
+
+  params.add_single_mutable(values_a.as_mutable_span());
+  params.add_readonly_single_input(values_cond.as_span());
+
+  MFContextBuilder context;
+  procedure_fn.call({1, 2, 3, 4}, params, context);
+
+  EXPECT_EQ(values_a[0], 1);
+  EXPECT_EQ(values_a[1], 25);
+  EXPECT_EQ(values_a[2], 113);
+  EXPECT_EQ(values_a[3], 116);
+  EXPECT_EQ(values_a[4], 22);
+}
+
+TEST(multi_function_procedure, EvaluateOne)
+{
+  /**
+   * procedure(int var1, int *var2) {
+   *   var2 = var1 + 10;
+   * }
+   */
+
+  int tot_evaluations = 0;
+  CustomMF_SI_SO<int, int> add_10_fn{"add_10", [&](int a) {
+                                       tot_evaluations++;
+                                       return a + 10;
+                                     }};
+
+  MFProcedure procedure;
+  MFProcedureBuilder builder{procedure};
+
+  MFVariable *var1 = &builder.add_single_input_parameter<int>();
+  auto [var2] = builder.add_call<1>(add_10_fn, {var1});
+  builder.add_destruct(*var1);
+  builder.add_return();
+  builder.add_output_parameter(*var2);
+
+  MFProcedureExecutor procedure_fn{"Evaluate One", procedure};
+  MFParamsBuilder params{procedure_fn, 5};
+
+  Array<int> values_out = {1, 2, 3, 4, 5};
+  params.add_readonly_single_input_value(1);
+  params.add_uninitialized_single_output(values_out.as_mutable_span());
+
+  MFContextBuilder context;
+  procedure_fn.call({0, 1, 3, 4}, params, context);
+
+  EXPECT_EQ(values_out[0], 11);
+  EXPECT_EQ(values_out[1], 11);
+  EXPECT_EQ(values_out[2], 3);
+  EXPECT_EQ(values_out[3], 11);
+  EXPECT_EQ(values_out[4], 11);
+  /* We expect only one evaluation, because the input is constant. */
+  EXPECT_EQ(tot_evaluations, 1);
+}
+
+TEST(multi_function_procedure, SimpleLoop)
+{
+  /**
+   * procedure(int count, int *out) {
+   *   out = 1;
+   *   int index = 0'
+   *   loop {
+   *     if (index >= count) {
+   *       break;
+   *     }
+   *     out *= 2;
+   *     index += 1;
+   *   }
+   *   out += 1000;
+   * }
+   */
+
+  CustomMF_Constant<int> const_1_fn{1};
+  CustomMF_Constant<int> const_0_fn{0};
+  CustomMF_SI_SI_SO<int, int, bool> greater_or_equal_fn{"greater or equal",
+                                                        [](int a, int b) { return a >= b; }};
+  CustomMF_SM<int> double_fn{"double", [](int &a) { a *= 2; }};
+  CustomMF_SM<int> add_1000_fn{"add 1000", [](int &a) { a += 1000; }};
+  CustomMF_SM<int> add_1_fn{"add 1", [](int &a) { a += 1; }};
+
+  MFProcedure procedure;
+  MFProcedureBuilder builder{procedure};
+
+  MFVariable *var_count = &builder.add_single_input_parameter<int>("count");
+  auto [var_out] = builder.add_call<1>(const_1_fn);
+  var_out->set_name("out");
+  auto [var_index] = builder.add_call<1>(const_0_fn);
+  var_index->set_name("index");
+
+  MFProcedureBuilder::Loop loop = builder.add_loop();
+  auto [var_condition] = builder.add_call<1>(greater_or_equal_fn, {var_index, var_count});
+  var_condition->set_name("condition");
+  MFProcedureBuilder::Branch branch = builder.add_branch(*var_condition);
+  branch.branch_true.add_destruct(*var_condition);
+  branch.branch_true.add_loop_break(loop);
+  branch.branch_false.add_destruct(*var_condition);
+  builder.set_cursor_after_branch(branch);
+  builder.add_call(double_fn, {var_out});
+  builder.add_call(add_1_fn, {var_index});
+  builder.add_loop_continue(loop);
+  builder.set_cursor_after_loop(loop);
+  builder.add_call(add_1000_fn, {var_out});
+  builder.add_destruct({var_count, var_index});
+  builder.add_return();
+  builder.add_output_parameter(*var_out);
+
+  EXPECT_TRUE(procedure.validate());
+
+  MFProcedureExecutor procedure_fn{"Simple Loop", procedure};
+  MFParamsBuilder params{procedure_fn, 5};
+
+  Array<int> counts = {4, 3, 7, 6, 4};
+  Array<int> results(5, -1);
+
+  params.add_readonly_single_input(counts.as_span());
+  params.add_uninitialized_single_output(results.as_mutable_span());
+
+  MFContextBuilder context;
+  procedure_fn.call({0, 1, 3, 4}, params, context);
+
+  EXPECT_EQ(results[0], 1016);
+  EXPECT_EQ(results[1], 1008);
+  EXPECT_EQ(results[2], -1);
+  EXPECT_EQ(results[3], 1064);
+  EXPECT_EQ(results[4], 1016);
+}
+
+TEST(multi_function_procedure, Vectors)
+{
+  /**
+   * procedure(vector<int> v1, vector<int> &v2, vector<int> *v3) {
+   *   v1.extend(v2);
+   *   int constant = 5;
+   *   v2.append(constant);
+   *   v2.extend(v1);
+   *   int len = sum(v2);
+   *   v3 = range(len);
+   * }
+   */
+
+  CreateRangeFunction create_range_fn;
+  ConcatVectorsFunction extend_fn;
+  GenericAppendFunction append_fn{CPPType::get<int>()};
+  SumVectorFunction sum_elements_fn;
+  CustomMF_Constant<int> constant_5_fn{5};
+
+  MFProcedure procedure;
+  MFProcedureBuilder builder{procedure};
+
+  MFVariable *var_v1 = &builder.add_input_parameter(MFDataType::ForVector<int>());
+  MFVariable *var_v2 = &builder.add_parameter(MFParamType::ForMutableVector(CPPType::get<int>()));
+  builder.add_call(extend_fn, {var_v1, var_v2});
+  auto [var_constant] = builder.add_call<1>(constant_5_fn);
+  builder.add_call(append_fn, {var_v2, var_constant});
+  builder.add_destruct(*var_constant);
+  builder.add_call(extend_fn, {var_v2, var_v1});
+  auto [var_len] = builder.add_call<1>(sum_elements_fn, {var_v2});
+  auto [var_v3] = builder.add_call<1>(create_range_fn, {var_len});
+  builder.add_destruct({var_v1, var_len});
+  builder.add_return();
+  builder.add_output_parameter(*var_v3);
+
+  EXPECT_TRUE(procedure.validate());
+
+  MFProcedureExecutor procedure_fn{"Vectors", procedure};
+  MFParamsBuilder params{procedure_fn, 5};
+
+  Array<int> v1 = {5, 2, 3};
+  GVectorArray v2{CPPType::get<int>(), 5};
+  GVectorArray v3{CPPType::get<int>(), 5};
+
+  int value_10 = 10;
+  v2.append(0, &value_10);
+  v2.append(4, &value_10);
+
+  params.add_readonly_vector_input(v1.as_span());
+  params.add_vector_mutable(v2);
+  params.add_vector_output(v3);
+
+  MFContextBuilder context;
+  procedure_fn.call({0, 1, 3, 4}, params, context);
+
+  EXPECT_EQ(v2[0].size(), 6);
+  EXPECT_EQ(v2[1].size(), 4);
+  EXPECT_EQ(v2[2].size(), 0);
+  EXPECT_EQ(v2[3].size(), 4);
+  EXPECT_EQ(v2[4].size(), 6);
+
+  EXPECT_EQ(v3[0].size(), 35);
+  EXPECT_EQ(v3[1].size(), 15);
+  EXPECT_EQ(v3[2].size(), 0);
+  EXPECT_EQ(v3[3].size(), 15);
+  EXPECT_EQ(v3[4].size(), 35);
+}
+
+TEST(multi_function_procedure, BufferReuse)
+{
+  /**
+   * procedure(int a, int *out) {
+   *   int b = a + 10;
+   *   int c = c + 10;
+   *   int d = d + 10;
+   *   int e = d + 10;
+   *   out = e + 10;
+   * }
+   */
+
+  CustomMF_SI_SO<int, int> add_10_fn{"add 10", [](int a) { return a + 10; }};
+
+  MFProcedure procedure;
+  MFProcedureBuilder builder{procedure};
+
+  MFVariable *var_a = &builder.add_single_input_parameter<int>();
+  auto [var_b] = builder.add_call<1>(add_10_fn, {var_a});
+  builder.add_destruct(*var_a);
+  auto [var_c] = builder.add_call<1>(add_10_fn, {var_b});
+  builder.add_destruct(*var_b);
+  auto [var_d] = builder.add_call<1>(add_10_fn, {var_c});
+  builder.add_destruct(*var_c);
+  auto [var_e] = builder.add_call<1>(add_10_fn, {var_d});
+  builder.add_destruct(*var_d);
+  auto [var_out] = builder.add_call<1>(add_10_fn, {var_e});
+  builder.add_destruct(*var_e);
+  builder.add_return();
+  builder.add_output_parameter(*var_out);
+
+  EXPECT_TRUE(procedure.validate());
+
+  MFProcedureExecutor procedure_fn{"Buffer Reuse", procedure};
+
+  Array<int> inputs = {4, 1, 6, 2, 3};
+  Array<int> results(5, -1);
+
+  MFParamsBuilder params{procedure_fn, 5};
+  params.add_readonly_single_input(inputs.as_span());
+  params.add_uninitialized_single_output(results.as_mutable_span());
+
+  MFContextBuilder context;
+  procedure_fn.call({0, 2, 3, 4}, params, context);
+
+  EXPECT_EQ(results[0], 54);
+  EXPECT_EQ(results[1], -1);
+  EXPECT_EQ(results[2], 56);
+  EXPECT_EQ(results[3], 52);
+  EXPECT_EQ(results[4], 53);
+}
+
+}  // namespace blender::fn::tests

source/blender/makesdna/DNA_customdata_types.h

@@ -31,6 +31,8 @@
 extern "C" {
 #endif
 
+struct AnonymousAttributeID;
+
 /** Descriptor and storage for a custom data layer. */
 typedef struct CustomDataLayer {
   /** Type of data in layer. */
@@ -53,6 +55,13 @@ typedef struct CustomDataLayer {
   char name[64];
   /** Layer data. */
   void *data;
+  /**
+   * Run-time identifier for this layer. If no one has a strong reference to this id anymore,
+   * the layer can be removed. The custom data layer only has a weak reference to the id, because
+   * otherwise there will always be a strong reference and the attribute can't be removed
+   * automatically.
+   */
+  const struct AnonymousAttributeID *anonymous_id;
 } CustomDataLayer;
 
 #define MAX_CUSTOMDATA_LAYER_NAME 64

source/blender/makesdna/DNA_node_types.h

@@ -1441,6 +1441,13 @@ typedef struct NodeGeometryCurveFill {
   uint8_t mode;
 } NodeGeometryCurveFill;
 
+typedef struct NodeGeometryAttributeCapture {
+  /* CustomDataType. */
+  int8_t data_type;
+  /* AttributeDomain. */
+  int8_t domain;
+} NodeGeometryAttributeCapture;
+
 /* script node mode */
 #define NODE_SCRIPT_INTERNAL 0
 #define NODE_SCRIPT_EXTERNAL 1

source/blender/makesdna/DNA_userdef_types.h

@@ -646,7 +646,8 @@ typedef struct UserDef_Experimental {
   char use_sculpt_tools_tilt;
   char use_extended_asset_browser;
   char use_override_templates;
-  char _pad[5];
+  char use_geometry_nodes_fields;
+  char _pad[4];
   /** `makesdna` does not allow empty structs. */
 } UserDef_Experimental;
 

source/blender/makesrna/intern/rna_nodetree.c

@@ -10284,6 +10284,26 @@ static void def_geo_curve_fill(StructRNA *srna)
   RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
 }
 
+static void def_geo_attribute_capture(StructRNA *srna)
+{
+  PropertyRNA *prop;
+
+  RNA_def_struct_sdna_from(srna, "NodeGeometryAttributeCapture", "storage");
+
+  prop = RNA_def_property(srna, "data_type", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, rna_enum_attribute_type_items);
+  RNA_def_property_enum_funcs(prop, NULL, NULL, "rna_GeometryNodeAttributeFill_type_itemf");
+  RNA_def_property_enum_default(prop, CD_PROP_FLOAT);
+  RNA_def_property_ui_text(prop, "Data Type", "Type of data stored in attribute");
+  RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_GeometryNode_socket_update");
+
+  prop = RNA_def_property(srna, "domain", PROP_ENUM, PROP_NONE);
+  RNA_def_property_enum_items(prop, rna_enum_attribute_domain_items);
+  RNA_def_property_enum_default(prop, ATTR_DOMAIN_POINT);
+  RNA_def_property_ui_text(prop, "Domain", "Which domain to store the data in");
+  RNA_def_property_update(prop, NC_NODE | NA_EDITED, "rna_Node_update");
+}
+
 /* -------------------------------------------------------------------------- */
 
 static void rna_def_shader_node(BlenderRNA *brna)

source/blender/makesrna/intern/rna_userdef.c

@@ -6300,6 +6300,10 @@ static void rna_def_userdef_experimental(BlenderRNA *brna)
   RNA_def_property_boolean_sdna(prop, NULL, "use_override_templates", 1);
   RNA_def_property_ui_text(
       prop, "Override Templates", "Enable library override template in the python API");
+
+  prop = RNA_def_property(srna, "use_geometry_nodes_fields", PROP_BOOLEAN, PROP_NONE);
+  RNA_def_property_boolean_sdna(prop, NULL, "use_geometry_nodes_fields", 1);
+  RNA_def_property_ui_text(prop, "Geometry Nodes Fields", "Enable field nodes in geometry nodes");
 }
 
 static void rna_def_userdef_addon_collection(BlenderRNA *brna, PropertyRNA *cprop)

source/blender/modifiers/intern/MOD_nodes.cc

@@ -85,6 +85,7 @@
 #include "NOD_geometry.h"
 #include "NOD_geometry_nodes_eval_log.hh"
 
+#include "FN_field.hh"
 #include "FN_multi_function.hh"
 
 using blender::destruct_ptr;
@@ -410,28 +411,36 @@ static void init_socket_cpp_value_from_property(const IDProperty &property,
 {
   switch (socket_value_type) {
     case SOCK_FLOAT: {
+      float value = 0.0f;
       if (property.type == IDP_FLOAT) {
-        *(float *)r_value = IDP_Float(&property);
+        value = IDP_Float(&property);
       }
       else if (property.type == IDP_DOUBLE) {
-        *(float *)r_value = (float)IDP_Double(&property);
+        value = (float)IDP_Double(&property);
       }
+      new (r_value) blender::fn::Field<float>(blender::fn::make_constant_field(value));
       break;
     }
     case SOCK_INT: {
-      *(int *)r_value = IDP_Int(&property);
+      int value = IDP_Int(&property);
+      new (r_value) blender::fn::Field<int>(blender::fn::make_constant_field(value));
       break;
     }
     case SOCK_VECTOR: {
-      copy_v3_v3((float *)r_value, (const float *)IDP_Array(&property));
+      float3 value;
+      copy_v3_v3(value, (const float *)IDP_Array(&property));
+      new (r_value) blender::fn::Field<float3>(blender::fn::make_constant_field(value));
       break;
     }
     case SOCK_BOOLEAN: {
-      *(bool *)r_value = IDP_Int(&property) != 0;
+      bool value = IDP_Int(&property) != 0;
+      new (r_value) blender::fn::Field<bool>(blender::fn::make_constant_field(value));
       break;
     }
     case SOCK_STRING: {
-      new (r_value) std::string(IDP_String(&property));
+      std::string value = IDP_String(&property);
+      new (r_value)
+          blender::fn::Field<std::string>(blender::fn::make_constant_field(std::move(value)));
       break;
     }
     case SOCK_OBJECT: {

source/blender/modifiers/intern/MOD_nodes_evaluator.cc

@@ -21,6 +21,8 @@
 
 #include "DEG_depsgraph_query.h"
 
+#include "FN_field.hh"
+#include "FN_field_cpp_type.hh"
 #include "FN_generic_value_map.hh"
 #include "FN_multi_function.hh"
 
@@ -33,6 +35,9 @@
 namespace blender::modifiers::geometry_nodes {
 
 using fn::CPPType;
+using fn::Field;
+using fn::FieldCPPType;
+using fn::GField;
 using fn::GValueMap;
 using nodes::GeoNodeExecParams;
 using namespace fn::multi_function_types;
@@ -858,11 +863,10 @@ class GeometryNodesEvaluator {
                                    const MultiFunction &fn,
                                    NodeState &node_state)
   {
-    MFContextBuilder fn_context;
-    MFParamsBuilder fn_params{fn, 1};
     LinearAllocator<> &allocator = local_allocators_.local();
 
     /* Prepare the inputs for the multi function. */
+    Vector<GField> input_fields;
     for (const int i : node->inputs().index_range()) {
       const InputSocketRef &socket_ref = node->input(i);
       if (!socket_ref.is_available()) {
@@ -873,24 +877,12 @@ class GeometryNodesEvaluator {
       BLI_assert(input_state.was_ready_for_execution);
       SingleInputValue &single_value = *input_state.value.single;
       BLI_assert(single_value.value != nullptr);
-      fn_params.add_readonly_single_input(GPointer{*input_state.type, single_value.value});
-    }
-    /* Prepare the outputs for the multi function. */
-    Vector<GMutablePointer> outputs;
-    for (const int i : node->outputs().index_range()) {
-      const OutputSocketRef &socket_ref = node->output(i);
-      if (!socket_ref.is_available()) {
-        continue;
-      }
-      const CPPType &type = *get_socket_cpp_type(socket_ref);
-      void *buffer = allocator.allocate(type.size(), type.alignment());
-      fn_params.add_uninitialized_single_output(GMutableSpan{type, buffer, 1});
-      outputs.append({type, buffer});
+      input_fields.append(std::move(*(GField *)single_value.value));
     }
 
-    fn.call(IndexRange(1), fn_params, fn_context);
+    auto operation = std::make_shared<fn::FieldOperation>(fn, std::move(input_fields));
 
-    /* Forward the computed outputs. */
+    /* Forward outputs. */
     int output_index = 0;
     for (const int i : node->outputs().index_range()) {
       const OutputSocketRef &socket_ref = node->output(i);
@@ -899,8 +891,9 @@ class GeometryNodesEvaluator {
       }
       OutputState &output_state = node_state.outputs[i];
       const DOutputSocket socket{node.context(), &socket_ref};
-      GMutablePointer value = outputs[output_index];
-      this->forward_output(socket, value);
+      const CPPType *cpp_type = get_socket_cpp_type(socket_ref);
+      GField &field = *allocator.construct<GField>(operation, output_index).release();
+      this->forward_output(socket, {cpp_type, &field});
       output_state.has_been_computed = true;
       output_index++;
     }
@@ -922,7 +915,7 @@ class GeometryNodesEvaluator {
       OutputState &output_state = node_state.outputs[socket->index()];
       output_state.has_been_computed = true;
       void *buffer = allocator.allocate(type->size(), type->alignment());
-      type->copy_construct(type->default_value(), buffer);
+      this->construct_default_value(*type, buffer);
       this->forward_output({node.context(), socket}, {*type, buffer});
     }
   }
@@ -1389,16 +1382,44 @@ class GeometryNodesEvaluator {
       return;
     }
 
+    const FieldCPPType *from_field_type = dynamic_cast<const FieldCPPType *>(&from_type);
+    const FieldCPPType *to_field_type = dynamic_cast<const FieldCPPType *>(&to_type);
+
+    if (from_field_type != nullptr && to_field_type != nullptr) {
+      const CPPType &from_base_type = from_field_type->field_type();
+      const CPPType &to_base_type = to_field_type->field_type();
+      if (conversions_.is_convertible(from_base_type, to_base_type)) {
+        const MultiFunction &fn = *conversions_.get_conversion_multi_function(
+            MFDataType::ForSingle(from_base_type), MFDataType::ForSingle(to_base_type));
+        const GField &from_field = *(const GField *)from_value;
+        auto operation = std::make_shared<fn::FieldOperation>(fn, Vector<GField>{from_field});
+        new (to_value) GField(std::move(operation), 0);
+        return;
+      }
+    }
     if (conversions_.is_convertible(from_type, to_type)) {
       /* Do the conversion if possible. */
       conversions_.convert_to_uninitialized(from_type, to_type, from_value, to_value);
     }
     else {
       /* Cannot convert, use default value instead. */
-      to_type.copy_construct(to_type.default_value(), to_value);
+      this->construct_default_value(to_type, to_value);
     }
   }
 
+  void construct_default_value(const CPPType &type, void *r_value)
+  {
+    if (const FieldCPPType *field_cpp_type = dynamic_cast<const FieldCPPType *>(&type)) {
+      const CPPType &base_type = field_cpp_type->field_type();
+      auto constant_fn = std::make_unique<fn::CustomMF_GenericConstant>(base_type,
+                                                                        base_type.default_value());
+      auto operation = std::make_shared<fn::FieldOperation>(std::move(constant_fn));
+      new (r_value) GField(std::move(operation), 0);
+      return;
+    }
+    type.copy_construct(type.default_value(), r_value);
+  }
+
   NodeState &get_node_state(const DNode node)
   {
     return *node_states_.lookup_key_as(node).state;

source/blender/nodes/CMakeLists.txt

@@ -142,6 +142,7 @@ set(SRC
   function/node_function_util.cc
 
   geometry/nodes/node_geo_align_rotation_to_vector.cc
+  geometry/nodes/node_geo_attribute_capture.cc
   geometry/nodes/node_geo_attribute_clamp.cc
   geometry/nodes/node_geo_attribute_color_ramp.cc
   geometry/nodes/node_geo_attribute_combine_xyz.cc
@@ -187,6 +188,9 @@ set(SRC
   geometry/nodes/node_geo_delete_geometry.cc
   geometry/nodes/node_geo_edge_split.cc
   geometry/nodes/node_geo_input_material.cc
+  geometry/nodes/node_geo_input_normal.cc
+  geometry/nodes/node_geo_input_position.cc
+  geometry/nodes/node_geo_input_index.cc
   geometry/nodes/node_geo_is_viewport.cc
   geometry/nodes/node_geo_join_geometry.cc
   geometry/nodes/node_geo_material_assign.cc
@@ -212,6 +216,7 @@ set(SRC
   geometry/nodes/node_geo_raycast.cc
   geometry/nodes/node_geo_select_by_material.cc
   geometry/nodes/node_geo_separate_components.cc
+  geometry/nodes/node_geo_set_position.cc
   geometry/nodes/node_geo_subdivision_surface.cc
   geometry/nodes/node_geo_switch.cc
   geometry/nodes/node_geo_transform.cc

source/blender/nodes/NOD_geometry.h

@@ -37,6 +37,7 @@ void register_node_type_geo_attribute_compare(void);
 void register_node_type_geo_attribute_convert(void);
 void register_node_type_geo_attribute_curve_map(void);
 void register_node_type_geo_attribute_fill(void);
+void register_node_type_geo_attribute_capture(void);
 void register_node_type_geo_attribute_map_range(void);
 void register_node_type_geo_attribute_math(void);
 void register_node_type_geo_attribute_mix(void);
@@ -71,7 +72,10 @@ void register_node_type_geo_curve_to_points(void);
 void register_node_type_geo_curve_trim(void);
 void register_node_type_geo_delete_geometry(void);
 void register_node_type_geo_edge_split(void);
+void register_node_type_geo_input_index(void);
 void register_node_type_geo_input_material(void);
+void register_node_type_geo_input_normal(void);
+void register_node_type_geo_input_position(void);
 void register_node_type_geo_is_viewport(void);
 void register_node_type_geo_join_geometry(void);
 void register_node_type_geo_material_assign(void);
@@ -99,6 +103,7 @@ void register_node_type_geo_sample_texture(void);
 void register_node_type_geo_select_by_handle_type(void);
 void register_node_type_geo_select_by_material(void);
 void register_node_type_geo_separate_components(void);
+void register_node_type_geo_set_position(void);
 void register_node_type_geo_subdivision_surface(void);
 void register_node_type_geo_switch(void);
 void register_node_type_geo_transform(void);

source/blender/nodes/NOD_geometry_exec.hh

@@ -16,7 +16,8 @@
 
 #pragma once
 
-#include "FN_generic_value_map.hh"
+#include "FN_field.hh"
+#include "FN_multi_function_builder.hh"
 
 #include "BKE_attribute_access.hh"
 #include "BKE_geometry_set.hh"
@@ -32,17 +33,24 @@ struct ModifierData;
 
 namespace blender::nodes {
 
+using bke::AttributeIDRef;
 using bke::geometry_set_realize_instances;
+using bke::GeometryComponentFieldContext;
 using bke::OutputAttribute;
 using bke::OutputAttribute_Typed;
 using bke::ReadAttributeLookup;
+using bke::StrongAnonymousAttributeID;
+using bke::WeakAnonymousAttributeID;
 using bke::WriteAttributeLookup;
 using fn::CPPType;
+using fn::Field;
+using fn::FieldInput;
+using fn::FieldOperation;
+using fn::GField;
 using fn::GMutablePointer;
 using fn::GMutableSpan;
 using fn::GPointer;
 using fn::GSpan;
-using fn::GValueMap;
 using fn::GVArray;
 using fn::GVArray_GSpan;
 using fn::GVArray_Span;
@@ -121,6 +129,14 @@ class GeoNodeExecParams {
   {
   }
 
+  template<typename T>
+  static inline constexpr bool is_stored_as_field_v = std::is_same_v<T, float> ||
+                                                      std::is_same_v<T, int> ||
+                                                      std::is_same_v<T, bool> ||
+                                                      std::is_same_v<T, ColorGeometry4f> ||
+                                                      std::is_same_v<T, float3> ||
+                                                      std::is_same_v<T, std::string>;
+
   /**
    * Get the input value for the input socket with the given identifier.
    *
@@ -142,11 +158,17 @@ class GeoNodeExecParams {
    */
   template<typename T> T extract_input(StringRef identifier)
   {
+    if constexpr (is_stored_as_field_v<T>) {
+      Field<T> field = this->extract_input<Field<T>>(identifier);
+      return fn::evaluate_constant_field(field);
+    }
+    else {
 #ifdef DEBUG
-    this->check_input_access(identifier, &CPPType::get<T>());
+      this->check_input_access(identifier, &CPPType::get<T>());
 #endif
-    GMutablePointer gvalue = this->extract_input(identifier);
-    return gvalue.relocate_out<T>();
+      GMutablePointer gvalue = this->extract_input(identifier);
+      return gvalue.relocate_out<T>();
+    }
   }
 
   /**
@@ -159,7 +181,13 @@ class GeoNodeExecParams {
     Vector<GMutablePointer> gvalues = provider_->extract_multi_input(identifier);
     Vector<T> values;
     for (GMutablePointer gvalue : gvalues) {
-      values.append(gvalue.relocate_out<T>());
+      if constexpr (is_stored_as_field_v<T>) {
+        const Field<T> &field = *gvalue.get<Field<T>>();
+        values.append(fn::evaluate_constant_field(field));
+      }
+      else {
+        values.append(gvalue.relocate_out<T>());
+      }
     }
     return values;
   }
@@ -167,14 +195,20 @@ class GeoNodeExecParams {
   /**
    * Get the input value for the input socket with the given identifier.
    */
-  template<typename T> const T &get_input(StringRef identifier) const
+  template<typename T> const T get_input(StringRef identifier) const
   {
+    if constexpr (is_stored_as_field_v<T>) {
+      const Field<T> &field = this->get_input<Field<T>>(identifier);
+      return fn::evaluate_constant_field(field);
+    }
+    else {
 #ifdef DEBUG
-    this->check_input_access(identifier, &CPPType::get<T>());
+      this->check_input_access(identifier, &CPPType::get<T>());
 #endif
-    GPointer gvalue = provider_->get_input(identifier);
-    BLI_assert(gvalue.is_type<T>());
-    return *(const T *)gvalue.get();
+      GPointer gvalue = provider_->get_input(identifier);
+      BLI_assert(gvalue.is_type<T>());
+      return *(const T *)gvalue.get();
+    }
   }
 
   /**
@@ -183,13 +217,19 @@ class GeoNodeExecParams {
   template<typename T> void set_output(StringRef identifier, T &&value)
   {
     using StoredT = std::decay_t<T>;
-    const CPPType &type = CPPType::get<std::decay_t<T>>();
+    if constexpr (is_stored_as_field_v<StoredT>) {
+      this->set_output<Field<StoredT>>(identifier,
+                                       fn::make_constant_field<StoredT>(std::forward<T>(value)));
+    }
+    else {
+      const CPPType &type = CPPType::get<StoredT>();
 #ifdef DEBUG
-    this->check_output_access(identifier, type);
+      this->check_output_access(identifier, type);
 #endif
-    GMutablePointer gvalue = provider_->alloc_output_value(type);
-    new (gvalue.get()) StoredT(std::forward<T>(value));
-    provider_->set_output(identifier, gvalue);
+      GMutablePointer gvalue = provider_->alloc_output_value(type);
+      new (gvalue.get()) StoredT(std::forward<T>(value));
+      provider_->set_output(identifier, gvalue);
+    }
   }
 
   /**

source/blender/nodes/NOD_static_types.h

@@ -276,6 +276,7 @@ DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_COMBINE_XYZ, def_geo_attribute_combine_
 DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_COMPARE, def_geo_attribute_attribute_compare, "ATTRIBUTE_COMPARE", AttributeCompare, "Attribute Compare", "")
 DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_CONVERT, def_geo_attribute_convert, "ATTRIBUTE_CONVERT", AttributeConvert, "Attribute Convert", "")
 DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_CURVE_MAP, def_geo_attribute_curve_map, "ATTRIBUTE_CURVE_MAP", AttributeCurveMap, "Attribute Curve Map", "")
+DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_CAPTURE, def_geo_attribute_capture, "ATTRIBUTE_CAPTURE", AttributeCapture, "Attribute Capture", "")
 DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_FILL, def_geo_attribute_fill, "ATTRIBUTE_FILL", AttributeFill, "Attribute Fill", "")
 DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_MAP_RANGE, def_geo_attribute_map_range, "ATTRIBUTE_MAP_RANGE", AttributeMapRange, "Attribute Map Range", "")
 DefNode(GeometryNode, GEO_NODE_ATTRIBUTE_MATH, def_geo_attribute_math, "ATTRIBUTE_MATH", AttributeMath, "Attribute Math", "")
@@ -304,8 +305,8 @@ DefNode(GeometryNode, GEO_NODE_CURVE_PRIMITIVE_SPIRAL, 0, "CURVE_PRIMITIVE_SPIRA
 DefNode(GeometryNode, GEO_NODE_CURVE_PRIMITIVE_STAR, 0, "CURVE_PRIMITIVE_STAR", CurveStar, "Star", "")
 DefNode(GeometryNode, GEO_NODE_CURVE_RESAMPLE, def_geo_curve_resample, "CURVE_RESAMPLE", CurveResample, "Resample Curve", "")
 DefNode(GeometryNode, GEO_NODE_CURVE_REVERSE, 0, "CURVE_REVERSE", CurveReverse, "Curve Reverse", "")
-DefNode(GeometryNode, GEO_NODE_CURVE_SET_HANDLES, def_geo_curve_set_handles, "CURVE_SET_HANDLES", CurveSetHandles, "Set Handle Type", "")
 DefNode(GeometryNode, GEO_NODE_CURVE_SELECT_HANDLES, def_geo_curve_select_handles, "CURVE_SELECT_HANDLES", CurveSelectHandles, "Select by Handle Type", "")
+DefNode(GeometryNode, GEO_NODE_CURVE_SET_HANDLES, def_geo_curve_set_handles, "CURVE_SET_HANDLES", CurveSetHandles, "Set Handle Type", "")
 DefNode(GeometryNode, GEO_NODE_CURVE_SPLINE_TYPE, def_geo_curve_spline_type, "CURVE_SPLINE_TYPE", CurveSplineType, "Set Spline Type", "")
 DefNode(GeometryNode, GEO_NODE_CURVE_SUBDIVIDE, def_geo_curve_subdivide, "CURVE_SUBDIVIDE", CurveSubdivide, "Curve Subdivide", "")
 DefNode(GeometryNode, GEO_NODE_CURVE_TO_MESH, 0, "CURVE_TO_MESH", CurveToMesh, "Curve to Mesh", "")
@@ -313,7 +314,10 @@ DefNode(GeometryNode, GEO_NODE_CURVE_TO_POINTS, def_geo_curve_to_points, "CURVE_
 DefNode(GeometryNode, GEO_NODE_CURVE_TRIM, def_geo_curve_trim, "CURVE_TRIM", CurveTrim, "Curve Trim", "")
 DefNode(GeometryNode, GEO_NODE_DELETE_GEOMETRY, 0, "DELETE_GEOMETRY", DeleteGeometry, "Delete Geometry", "")
 DefNode(GeometryNode, GEO_NODE_EDGE_SPLIT, 0, "EDGE_SPLIT", EdgeSplit, "Edge Split", "")
+DefNode(GeometryNode, GEO_NODE_INPUT_INDEX, 0, "INDEX", InputIndex, "Index", "")
 DefNode(GeometryNode, GEO_NODE_INPUT_MATERIAL, def_geo_input_material, "INPUT_MATERIAL", InputMaterial, "Material", "")
+DefNode(GeometryNode, GEO_NODE_INPUT_NORMAL, 0, "INPUT_NORMAL", InputNormal, "Normal", "")
+DefNode(GeometryNode, GEO_NODE_INPUT_POSITION, 0, "POSITION", InputPosition, "Position", "")
 DefNode(GeometryNode, GEO_NODE_IS_VIEWPORT, 0, "IS_VIEWPORT", IsViewport, "Is Viewport", "")
 DefNode(GeometryNode, GEO_NODE_JOIN_GEOMETRY, 0, "JOIN_GEOMETRY", JoinGeometry, "Join Geometry", "")
 DefNode(GeometryNode, GEO_NODE_MATERIAL_ASSIGN, 0, "MATERIAL_ASSIGN", MaterialAssign, "Material Assign", "")
@@ -339,6 +343,7 @@ DefNode(GeometryNode, GEO_NODE_POINTS_TO_VOLUME, def_geo_points_to_volume, "POIN
 DefNode(GeometryNode, GEO_NODE_RAYCAST, def_geo_raycast, "RAYCAST", Raycast, "Raycast", "")
 DefNode(GeometryNode, GEO_NODE_SELECT_BY_MATERIAL, 0, "SELECT_BY_MATERIAL", SelectByMaterial, "Select by Material", "")
 DefNode(GeometryNode, GEO_NODE_SEPARATE_COMPONENTS, 0, "SEPARATE_COMPONENTS", SeparateComponents, "Separate Components", "")
+DefNode(GeometryNode, GEO_NODE_SET_POSITION, 0, "SET_POSITION", SetPosition, "Set Position", "")
 DefNode(GeometryNode, GEO_NODE_SUBDIVISION_SURFACE, def_geo_subdivision_surface, "SUBDIVISION_SURFACE", SubdivisionSurface, "Subdivision Surface", "")
 DefNode(GeometryNode, GEO_NODE_SWITCH, def_geo_switch, "SWITCH", Switch, "Switch", "")
 DefNode(GeometryNode, GEO_NODE_TRANSFORM, 0, "TRANSFORM", Transform, "Transform", "")

source/blender/nodes/geometry/node_geometry_util.hh

@@ -84,7 +84,7 @@ struct CurveToPointsResults {
   MutableSpan<float> radii;
   MutableSpan<float> tilts;
 
-  Map<std::string, GMutableSpan> point_attributes;
+  Map<AttributeIDRef, GMutableSpan> point_attributes;
 
   MutableSpan<float3> tangents;
   MutableSpan<float3> normals;

source/blender/nodes/geometry/nodes/node_geo_attribute_capture.cc

@@ -0,0 +1,210 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "UI_interface.h"
+#include "UI_resources.h"
+
+#include "BKE_attribute_math.hh"
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes {
+
+static void geo_node_attribute_capture_declare(NodeDeclarationBuilder &b)
+{
+  b.add_input<decl::Geometry>("Geometry");
+  b.add_input<decl::Vector>("Value");
+  b.add_input<decl::Float>("Value", "Value_001");
+  b.add_input<decl::Color>("Value", "Value_002");
+  b.add_input<decl::Bool>("Value", "Value_003");
+  b.add_input<decl::Int>("Value", "Value_004");
+
+  b.add_output<decl::Geometry>("Geometry");
+  b.add_output<decl::Vector>("Attribute");
+  b.add_output<decl::Float>("Attribute", "Attribute_001");
+  b.add_output<decl::Color>("Attribute", "Attribute_002");
+  b.add_output<decl::Bool>("Attribute", "Attribute_003");
+  b.add_output<decl::Int>("Attribute", "Attribute_004");
+}
+
+static void geo_node_attribute_capture_layout(uiLayout *layout,
+                                              bContext *UNUSED(C),
+                                              PointerRNA *ptr)
+{
+  uiLayoutSetPropSep(layout, true);
+  uiLayoutSetPropDecorate(layout, false);
+  uiItemR(layout, ptr, "domain", 0, "", ICON_NONE);
+  uiItemR(layout, ptr, "data_type", 0, "", ICON_NONE);
+}
+
+static void geo_node_attribute_capture_init(bNodeTree *UNUSED(tree), bNode *node)
+{
+  NodeGeometryAttributeCapture *data = (NodeGeometryAttributeCapture *)MEM_callocN(
+      sizeof(NodeGeometryAttributeCapture), __func__);
+  data->data_type = CD_PROP_FLOAT;
+  data->domain = ATTR_DOMAIN_POINT;
+
+  node->storage = data;
+}
+
+static void geo_node_attribute_capture_update(bNodeTree *UNUSED(ntree), bNode *node)
+{
+  const NodeGeometryAttributeCapture &storage = *(const NodeGeometryAttributeCapture *)
+                                                     node->storage;
+  const CustomDataType data_type = static_cast<CustomDataType>(storage.data_type);
+
+  bNodeSocket *socket_value_attribute_name = (bNodeSocket *)node->inputs.first;
+  bNodeSocket *socket_value_vector = socket_value_attribute_name->next;
+  bNodeSocket *socket_value_float = socket_value_vector->next;
+  bNodeSocket *socket_value_color4f = socket_value_float->next;
+  bNodeSocket *socket_value_boolean = socket_value_color4f->next;
+  bNodeSocket *socket_value_int32 = socket_value_boolean->next;
+
+  nodeSetSocketAvailability(socket_value_vector, data_type == CD_PROP_FLOAT3);
+  nodeSetSocketAvailability(socket_value_float, data_type == CD_PROP_FLOAT);
+  nodeSetSocketAvailability(socket_value_color4f, data_type == CD_PROP_COLOR);
+  nodeSetSocketAvailability(socket_value_boolean, data_type == CD_PROP_BOOL);
+  nodeSetSocketAvailability(socket_value_int32, data_type == CD_PROP_INT32);
+
+  bNodeSocket *out_socket_value_attribute_name = (bNodeSocket *)node->outputs.first;
+  bNodeSocket *out_socket_value_vector = out_socket_value_attribute_name->next;
+  bNodeSocket *out_socket_value_float = out_socket_value_vector->next;
+  bNodeSocket *out_socket_value_color4f = out_socket_value_float->next;
+  bNodeSocket *out_socket_value_boolean = out_socket_value_color4f->next;
+  bNodeSocket *out_socket_value_int32 = out_socket_value_boolean->next;
+
+  nodeSetSocketAvailability(out_socket_value_vector, data_type == CD_PROP_FLOAT3);
+  nodeSetSocketAvailability(out_socket_value_float, data_type == CD_PROP_FLOAT);
+  nodeSetSocketAvailability(out_socket_value_color4f, data_type == CD_PROP_COLOR);
+  nodeSetSocketAvailability(out_socket_value_boolean, data_type == CD_PROP_BOOL);
+  nodeSetSocketAvailability(out_socket_value_int32, data_type == CD_PROP_INT32);
+}
+
+static void try_capture_field_on_geometry(GeometryComponent &component,
+                                          const AttributeIDRef &attribute_id,
+                                          const AttributeDomain domain,
+                                          const GField &field)
+{
+  GeometryComponentFieldContext field_context{component, domain};
+  const int domain_size = component.attribute_domain_size(domain);
+  const IndexMask mask{IndexMask(domain_size)};
+
+  const CustomDataType data_type = bke::cpp_type_to_custom_data_type(field.cpp_type());
+  OutputAttribute output_attribute = component.attribute_try_get_for_output_only(
+      attribute_id, domain, data_type);
+
+  fn::FieldEvaluator evaluator{field_context, &mask};
+  evaluator.add_with_destination(field, output_attribute.varray());
+  evaluator.evaluate();
+
+  output_attribute.save();
+}
+
+static void geo_node_attribute_capture_exec(GeoNodeExecParams params)
+{
+  GeometrySet geometry_set = params.extract_input<GeometrySet>("Geometry");
+
+  geometry_set = bke::geometry_set_realize_instances(geometry_set);
+
+  const bNode &node = params.node();
+  const NodeGeometryAttributeCapture &storage = *(const NodeGeometryAttributeCapture *)
+                                                     node.storage;
+  const CustomDataType data_type = static_cast<CustomDataType>(storage.data_type);
+  const AttributeDomain domain = static_cast<AttributeDomain>(storage.domain);
+
+  GField field;
+  switch (data_type) {
+    case CD_PROP_FLOAT:
+      field = params.get_input<Field<float>>("Value_001");
+      break;
+    case CD_PROP_FLOAT3:
+      field = params.get_input<Field<float3>>("Value");
+      break;
+    case CD_PROP_COLOR:
+      field = params.get_input<Field<ColorGeometry4f>>("Value_002");
+      break;
+    case CD_PROP_BOOL:
+      field = params.get_input<Field<bool>>("Value_003");
+      break;
+    case CD_PROP_INT32:
+      field = params.get_input<Field<int>>("Value_004");
+      break;
+    default:
+      break;
+  }
+
+  WeakAnonymousAttributeID anonymous_id{"Attribute Capture"};
+  const CPPType &type = field.cpp_type();
+
+  static const Array<GeometryComponentType> types = {
+      GEO_COMPONENT_TYPE_MESH, GEO_COMPONENT_TYPE_POINT_CLOUD, GEO_COMPONENT_TYPE_CURVE};
+  for (const GeometryComponentType type : types) {
+    if (geometry_set.has(type)) {
+      GeometryComponent &component = geometry_set.get_component_for_write(type);
+      try_capture_field_on_geometry(component, anonymous_id.get(), domain, field);
+    }
+  }
+
+  GField output_field{
+      std::make_shared<bke::AnonymousAttributeFieldInput>(std::move(anonymous_id), type)};
+
+  switch (data_type) {
+    case CD_PROP_FLOAT: {
+      params.set_output("Attribute_001", Field<float>(output_field));
+      break;
+    }
+    case CD_PROP_FLOAT3: {
+      params.set_output("Attribute", Field<float3>(output_field));
+      break;
+    }
+    case CD_PROP_COLOR: {
+      params.set_output("Attribute_002", Field<ColorGeometry4f>(output_field));
+      break;
+    }
+    case CD_PROP_BOOL: {
+      params.set_output("Attribute_003", Field<bool>(output_field));
+      break;
+    }
+    case CD_PROP_INT32: {
+      params.set_output("Attribute_004", Field<int>(output_field));
+      break;
+    }
+    default:
+      break;
+  }
+
+  params.set_output("Geometry", geometry_set);
+}
+
+}  // namespace blender::nodes
+
+void register_node_type_geo_attribute_capture()
+{
+  static bNodeType ntype;
+
+  geo_node_type_base(
+      &ntype, GEO_NODE_ATTRIBUTE_CAPTURE, "Attribute Capture", NODE_CLASS_ATTRIBUTE, 0);
+  node_type_storage(&ntype,
+                    "NodeGeometryAttributeCapture",
+                    node_free_standard_storage,
+                    node_copy_standard_storage);
+  node_type_init(&ntype, blender::nodes::geo_node_attribute_capture_init);
+  node_type_update(&ntype, blender::nodes::geo_node_attribute_capture_update);
+  ntype.declare = blender::nodes::geo_node_attribute_capture_declare;
+  ntype.geometry_node_execute = blender::nodes::geo_node_attribute_capture_exec;
+  ntype.draw_buttons = blender::nodes::geo_node_attribute_capture_layout;
+  nodeRegisterType(&ntype);
+}

source/blender/nodes/geometry/nodes/node_geo_curve_endpoints.cc

@@ -56,25 +56,26 @@ static void copy_spline_domain_attributes(const CurveComponent &curve_component,
                                           Span<int> offsets,
                                           PointCloudComponent &points)
 {
-  curve_component.attribute_foreach([&](StringRefNull name, const AttributeMetaData &meta_data) {
-    if (meta_data.domain != ATTR_DOMAIN_CURVE) {
-      return true;
-    }
-    GVArrayPtr spline_attribute = curve_component.attribute_get_for_read(
-        name, ATTR_DOMAIN_CURVE, meta_data.data_type);
+  curve_component.attribute_foreach(
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        if (meta_data.domain != ATTR_DOMAIN_CURVE) {
+          return true;
+        }
+        GVArrayPtr spline_attribute = curve_component.attribute_get_for_read(
+            attribute_id, ATTR_DOMAIN_CURVE, meta_data.data_type);
 
-    OutputAttribute result_attribute = points.attribute_try_get_for_output_only(
-        name, ATTR_DOMAIN_POINT, meta_data.data_type);
-    GMutableSpan result = result_attribute.as_span();
+        OutputAttribute result_attribute = points.attribute_try_get_for_output_only(
+            attribute_id, ATTR_DOMAIN_POINT, meta_data.data_type);
+        GMutableSpan result = result_attribute.as_span();
 
-    /* Only copy the attributes of splines in the offsets. */
-    for (const int i : offsets.index_range()) {
-      spline_attribute->get(offsets[i], result[i]);
-    }
+        /* Only copy the attributes of splines in the offsets. */
+        for (const int i : offsets.index_range()) {
+          spline_attribute->get(offsets[i], result[i]);
+        }
 
-    result_attribute.save();
-    return true;
-  });
+        result_attribute.save();
+        return true;
+      });
 }
 
 /**
@@ -124,20 +125,20 @@ static void copy_endpoint_attributes(Span<SplinePtr> splines,
 
       /* Copy the point attribute data over. */
       for (const auto &item : start_data.point_attributes.items()) {
-        const StringRef name = item.key;
+        const AttributeIDRef attribute_id = item.key;
         GMutableSpan point_span = item.value;
 
-        BLI_assert(spline.attributes.get_for_read(name));
-        GSpan spline_span = *spline.attributes.get_for_read(name);
+        BLI_assert(spline.attributes.get_for_read(attribute_id));
+        GSpan spline_span = *spline.attributes.get_for_read(attribute_id);
         blender::fn::GVArray_For_GSpan(spline_span).get(0, point_span[i]);
       }
 
       for (const auto &item : end_data.point_attributes.items()) {
-        const StringRef name = item.key;
+        const AttributeIDRef attribute_id = item.key;
         GMutableSpan point_span = item.value;
 
-        BLI_assert(spline.attributes.get_for_read(name));
-        GSpan spline_span = *spline.attributes.get_for_read(name);
+        BLI_assert(spline.attributes.get_for_read(attribute_id));
+        GSpan spline_span = *spline.attributes.get_for_read(attribute_id);
         blender::fn::GVArray_For_GSpan(spline_span).get(spline.size() - 1, point_span[i]);
       }
     }

source/blender/nodes/geometry/nodes/node_geo_curve_resample.cc

@@ -84,14 +84,14 @@ static SplinePtr resample_spline(const Spline &input_spline, const int count)
                              input_spline.radii().first());
     output_spline->attributes.reallocate(1);
     input_spline.attributes.foreach_attribute(
-        [&](StringRefNull name, const AttributeMetaData &meta_data) {
-          std::optional<GSpan> src = input_spline.attributes.get_for_read(name);
+        [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+          std::optional<GSpan> src = input_spline.attributes.get_for_read(attribute_id);
           BLI_assert(src);
-          if (!output_spline->attributes.create(name, meta_data.data_type)) {
+          if (!output_spline->attributes.create(attribute_id, meta_data.data_type)) {
             BLI_assert_unreachable();
             return false;
           }
-          std::optional<GMutableSpan> dst = output_spline->attributes.get_for_write(name);
+          std::optional<GMutableSpan> dst = output_spline->attributes.get_for_write(attribute_id);
           if (!dst) {
             BLI_assert_unreachable();
             return false;
@@ -122,15 +122,15 @@ static SplinePtr resample_spline(const Spline &input_spline, const int count)
 
   output_spline->attributes.reallocate(count);
   input_spline.attributes.foreach_attribute(
-      [&](StringRefNull name, const AttributeMetaData &meta_data) {
-        std::optional<GSpan> input_attribute = input_spline.attributes.get_for_read(name);
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        std::optional<GSpan> input_attribute = input_spline.attributes.get_for_read(attribute_id);
         BLI_assert(input_attribute);
-        if (!output_spline->attributes.create(name, meta_data.data_type)) {
+        if (!output_spline->attributes.create(attribute_id, meta_data.data_type)) {
           BLI_assert_unreachable();
           return false;
         }
         std::optional<GMutableSpan> output_attribute = output_spline->attributes.get_for_write(
-            name);
+            attribute_id);
         if (!output_attribute) {
           BLI_assert_unreachable();
           return false;

source/blender/nodes/geometry/nodes/node_geo_curve_reverse.cc

@@ -83,9 +83,9 @@ static void geo_node_curve_reverse_exec(GeoNodeExecParams params)
       reverse_data<float>(splines[i]->tilts());
 
       splines[i]->attributes.foreach_attribute(
-          [&](StringRefNull name, const AttributeMetaData &meta_data) {
+          [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
             std::optional<blender::fn::GMutableSpan> output_attribute =
-                splines[i]->attributes.get_for_write(name);
+                splines[i]->attributes.get_for_write(attribute_id);
             if (!output_attribute) {
               BLI_assert_unreachable();
               return false;

source/blender/nodes/geometry/nodes/node_geo_curve_spline_type.cc

@@ -74,14 +74,14 @@ template<typename CopyFn>
 static void copy_attributes(const Spline &input_spline, Spline &output_spline, CopyFn copy_fn)
 {
   input_spline.attributes.foreach_attribute(
-      [&](StringRefNull name, const AttributeMetaData &meta_data) {
-        std::optional<GSpan> src = input_spline.attributes.get_for_read(name);
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        std::optional<GSpan> src = input_spline.attributes.get_for_read(attribute_id);
         BLI_assert(src);
-        if (!output_spline.attributes.create(name, meta_data.data_type)) {
+        if (!output_spline.attributes.create(attribute_id, meta_data.data_type)) {
           BLI_assert_unreachable();
           return false;
         }
-        std::optional<GMutableSpan> dst = output_spline.attributes.get_for_write(name);
+        std::optional<GMutableSpan> dst = output_spline.attributes.get_for_write(attribute_id);
         if (!dst) {
           BLI_assert_unreachable();
           return false;

source/blender/nodes/geometry/nodes/node_geo_curve_subdivide.cc

@@ -283,16 +283,16 @@ static void subdivide_dynamic_attributes(const Spline &src_spline,
 {
   const bool is_cyclic = src_spline.is_cyclic();
   src_spline.attributes.foreach_attribute(
-      [&](StringRefNull name, const AttributeMetaData &meta_data) {
-        std::optional<GSpan> src = src_spline.attributes.get_for_read(name);
+      [&](const bke::AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        std::optional<GSpan> src = src_spline.attributes.get_for_read(attribute_id);
         BLI_assert(src);
 
-        if (!dst_spline.attributes.create(name, meta_data.data_type)) {
+        if (!dst_spline.attributes.create(attribute_id, meta_data.data_type)) {
           /* Since the source spline of the same type had the attribute, adding it should work. */
           BLI_assert_unreachable();
         }
 
-        std::optional<GMutableSpan> dst = dst_spline.attributes.get_for_write(name);
+        std::optional<GMutableSpan> dst = dst_spline.attributes.get_for_write(attribute_id);
         BLI_assert(dst);
 
         attribute_math::convert_to_static_type(dst->type(), [&](auto dummy) {

source/blender/nodes/geometry/nodes/node_geo_curve_to_points.cc

@@ -115,21 +115,21 @@ static Array<int> calculate_spline_point_offsets(GeoNodeExecParams &params,
 }
 
 static GMutableSpan create_attribute_and_retrieve_span(PointCloudComponent &points,
-                                                       const StringRef name,
+                                                       const AttributeIDRef &attribute_id,
                                                        const CustomDataType data_type)
 {
-  points.attribute_try_create(name, ATTR_DOMAIN_POINT, data_type, AttributeInitDefault());
-  WriteAttributeLookup attribute = points.attribute_try_get_for_write(name);
+  points.attribute_try_create(attribute_id, ATTR_DOMAIN_POINT, data_type, AttributeInitDefault());
+  WriteAttributeLookup attribute = points.attribute_try_get_for_write(attribute_id);
   BLI_assert(attribute);
   return attribute.varray->get_internal_span();
 }
 
 template<typename T>
 static MutableSpan<T> create_attribute_and_retrieve_span(PointCloudComponent &points,
-                                                         const StringRef name)
+                                                         const AttributeIDRef &attribute_id)
 {
   GMutableSpan attribute = create_attribute_and_retrieve_span(
-      points, name, bke::cpp_type_to_custom_data_type(CPPType::get<T>()));
+      points, attribute_id, bke::cpp_type_to_custom_data_type(CPPType::get<T>()));
   return attribute.typed<T>();
 }
 
@@ -147,9 +147,10 @@ CurveToPointsResults curve_to_points_create_result_attributes(PointCloudComponen
   /* Because of the invariants of the curve component, we use the attributes of the
    * first spline as a representative for the attribute meta data all splines. */
   curve.splines().first()->attributes.foreach_attribute(
-      [&](StringRefNull name, const AttributeMetaData &meta_data) {
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
         attributes.point_attributes.add_new(
-            name, create_attribute_and_retrieve_span(points, name, meta_data.data_type));
+            attribute_id,
+            create_attribute_and_retrieve_span(points, attribute_id, meta_data.data_type));
         return true;
       },
       ATTR_DOMAIN_POINT);
@@ -179,12 +180,12 @@ static void copy_evaluated_point_attributes(Span<SplinePtr> splines,
       spline.interpolate_to_evaluated(spline.radii())->materialize(data.radii.slice(offset, size));
       spline.interpolate_to_evaluated(spline.tilts())->materialize(data.tilts.slice(offset, size));
 
-      for (const Map<std::string, GMutableSpan>::Item &item : data.point_attributes.items()) {
-        const StringRef name = item.key;
+      for (const Map<AttributeIDRef, GMutableSpan>::Item &item : data.point_attributes.items()) {
+        const AttributeIDRef attribute_id = item.key;
         GMutableSpan point_span = item.value;
 
-        BLI_assert(spline.attributes.get_for_read(name));
-        GSpan spline_span = *spline.attributes.get_for_read(name);
+        BLI_assert(spline.attributes.get_for_read(attribute_id));
+        GSpan spline_span = *spline.attributes.get_for_read(attribute_id);
 
         spline.interpolate_to_evaluated(spline_span)
             ->materialize(point_span.slice(offset, size).data());
@@ -222,12 +223,12 @@ static void copy_uniform_sample_point_attributes(Span<SplinePtr> splines,
                                               uniform_samples,
                                               data.tilts.slice(offset, size));
 
-      for (const Map<std::string, GMutableSpan>::Item &item : data.point_attributes.items()) {
-        const StringRef name = item.key;
+      for (const Map<AttributeIDRef, GMutableSpan>::Item &item : data.point_attributes.items()) {
+        const AttributeIDRef attribute_id = item.key;
         GMutableSpan point_span = item.value;
 
-        BLI_assert(spline.attributes.get_for_read(name));
-        GSpan spline_span = *spline.attributes.get_for_read(name);
+        BLI_assert(spline.attributes.get_for_read(attribute_id));
+        GSpan spline_span = *spline.attributes.get_for_read(attribute_id);
 
         spline.sample_with_index_factors(*spline.interpolate_to_evaluated(spline_span),
                                          uniform_samples,
@@ -257,31 +258,32 @@ static void copy_spline_domain_attributes(const CurveComponent &curve_component,
                                           Span<int> offsets,
                                           PointCloudComponent &points)
 {
-  curve_component.attribute_foreach([&](StringRefNull name, const AttributeMetaData &meta_data) {
-    if (meta_data.domain != ATTR_DOMAIN_CURVE) {
-      return true;
-    }
-    GVArrayPtr spline_attribute = curve_component.attribute_get_for_read(
-        name, ATTR_DOMAIN_CURVE, meta_data.data_type);
-    const CPPType &type = spline_attribute->type();
+  curve_component.attribute_foreach(
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        if (meta_data.domain != ATTR_DOMAIN_CURVE) {
+          return true;
+        }
+        GVArrayPtr spline_attribute = curve_component.attribute_get_for_read(
+            attribute_id, ATTR_DOMAIN_CURVE, meta_data.data_type);
+        const CPPType &type = spline_attribute->type();
 
-    OutputAttribute result_attribute = points.attribute_try_get_for_output_only(
-        name, ATTR_DOMAIN_POINT, meta_data.data_type);
-    GMutableSpan result = result_attribute.as_span();
+        OutputAttribute result_attribute = points.attribute_try_get_for_output_only(
+            attribute_id, ATTR_DOMAIN_POINT, meta_data.data_type);
+        GMutableSpan result = result_attribute.as_span();
 
-    for (const int i : IndexRange(spline_attribute->size())) {
-      const int offset = offsets[i];
-      const int size = offsets[i + 1] - offsets[i];
-      if (size != 0) {
-        BUFFER_FOR_CPP_TYPE_VALUE(type, buffer);
-        spline_attribute->get(i, buffer);
-        type.fill_assign_n(buffer, result[offset], size);
-      }
-    }
+        for (const int i : IndexRange(spline_attribute->size())) {
+          const int offset = offsets[i];
+          const int size = offsets[i + 1] - offsets[i];
+          if (size != 0) {
+            BUFFER_FOR_CPP_TYPE_VALUE(type, buffer);
+            spline_attribute->get(i, buffer);
+            type.fill_assign_n(buffer, result[offset], size);
+          }
+        }
 
-    result_attribute.save();
-    return true;
-  });
+        result_attribute.save();
+        return true;
+      });
 }
 
 void curve_create_default_rotation_attribute(Span<float3> tangents,

source/blender/nodes/geometry/nodes/node_geo_curve_trim.cc

@@ -158,8 +158,8 @@ static void trim_poly_spline(Spline &spline,
   linear_trim_data<float>(start, end, spline.tilts());
 
   spline.attributes.foreach_attribute(
-      [&](StringRefNull name, const AttributeMetaData &UNUSED(meta_data)) {
-        std::optional<GMutableSpan> src = spline.attributes.get_for_write(name);
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &UNUSED(meta_data)) {
+        std::optional<GMutableSpan> src = spline.attributes.get_for_write(attribute_id);
         BLI_assert(src);
         attribute_math::convert_to_static_type(src->type(), [&](auto dummy) {
           using T = decltype(dummy);
@@ -193,14 +193,14 @@ static PolySpline trim_nurbs_spline(const Spline &spline,
 
   /* Copy generic attribute data. */
   spline.attributes.foreach_attribute(
-      [&](StringRefNull name, const AttributeMetaData &meta_data) {
-        std::optional<GSpan> src = spline.attributes.get_for_read(name);
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        std::optional<GSpan> src = spline.attributes.get_for_read(attribute_id);
         BLI_assert(src);
-        if (!new_spline.attributes.create(name, meta_data.data_type)) {
+        if (!new_spline.attributes.create(attribute_id, meta_data.data_type)) {
           BLI_assert_unreachable();
           return false;
         }
-        std::optional<GMutableSpan> dst = new_spline.attributes.get_for_write(name);
+        std::optional<GMutableSpan> dst = new_spline.attributes.get_for_write(attribute_id);
         BLI_assert(dst);
 
         attribute_math::convert_to_static_type(src->type(), [&](auto dummy) {
@@ -249,8 +249,8 @@ static void trim_bezier_spline(Spline &spline,
   linear_trim_data<float>(start, end, bezier_spline.radii());
   linear_trim_data<float>(start, end, bezier_spline.tilts());
   spline.attributes.foreach_attribute(
-      [&](StringRefNull name, const AttributeMetaData &UNUSED(meta_data)) {
-        std::optional<GMutableSpan> src = spline.attributes.get_for_write(name);
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &UNUSED(meta_data)) {
+        std::optional<GMutableSpan> src = spline.attributes.get_for_write(attribute_id);
         BLI_assert(src);
         attribute_math::convert_to_static_type(src->type(), [&](auto dummy) {
           using T = decltype(dummy);

source/blender/nodes/geometry/nodes/node_geo_delete_geometry.cc

@@ -93,17 +93,17 @@ static void copy_dynamic_attributes(const CustomDataAttributes &src,
                                     const IndexMask mask)
 {
   src.foreach_attribute(
-      [&](StringRefNull name, const AttributeMetaData &meta_data) {
-        std::optional<GSpan> src_attribute = src.get_for_read(name);
+      [&](const AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        std::optional<GSpan> src_attribute = src.get_for_read(attribute_id);
         BLI_assert(src_attribute);
 
-        if (!dst.create(name, meta_data.data_type)) {
+        if (!dst.create(attribute_id, meta_data.data_type)) {
           /* Since the source spline of the same type had the attribute, adding it should work.
            */
           BLI_assert_unreachable();
         }
 
-        std::optional<GMutableSpan> new_attribute = dst.get_for_write(name);
+        std::optional<GMutableSpan> new_attribute = dst.get_for_write(attribute_id);
         BLI_assert(new_attribute);
 
         attribute_math::convert_to_static_type(new_attribute->type(), [&](auto dummy) {

source/blender/nodes/geometry/nodes/node_geo_input_index.cc

@@ -0,0 +1,60 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes {
+
+static void geo_node_input_index_declare(NodeDeclarationBuilder &b)
+{
+  b.add_output<decl::Int>("Index");
+}
+
+class IndexFieldInput final : public fn::FieldInput {
+ public:
+  IndexFieldInput() : FieldInput(CPPType::get<int>(), "Index")
+  {
+  }
+
+  const GVArray *get_varray_for_context(const fn::FieldContext &UNUSED(context),
+                                        IndexMask mask,
+                                        ResourceScope &scope) const final
+  {
+    /* TODO: Investigate a similar method to IndexRange::as_span() */
+    auto index_func = [](int i) { return i; };
+    return &scope.construct<
+        fn::GVArray_For_EmbeddedVArray<int, VArray_For_Func<int, decltype(index_func)>>>(
+        __func__, mask.min_array_size(), mask.min_array_size(), index_func);
+  }
+};
+
+static void geo_node_input_index_exec(GeoNodeExecParams params)
+{
+  Field<int> index_field{std::make_shared<IndexFieldInput>()};
+  params.set_output("Index", std::move(index_field));
+}
+
+}  // namespace blender::nodes
+
+void register_node_type_geo_input_index()
+{
+  static bNodeType ntype;
+
+  geo_node_type_base(&ntype, GEO_NODE_INPUT_INDEX, "Index", NODE_CLASS_INPUT, 0);
+  ntype.geometry_node_execute = blender::nodes::geo_node_input_index_exec;
+  ntype.declare = blender::nodes::geo_node_input_index_declare;
+  nodeRegisterType(&ntype);
+}

source/blender/nodes/geometry/nodes/node_geo_input_normal.cc

@@ -0,0 +1,211 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "DNA_mesh_types.h"
+#include "DNA_meshdata_types.h"
+
+#include "BKE_mesh.h"
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes {
+
+static void geo_node_input_normal_declare(NodeDeclarationBuilder &b)
+{
+  b.add_output<decl::Vector>("Normal");
+}
+
+static GVArrayPtr mesh_face_normals(const Mesh &mesh,
+                                    const Span<MVert> verts,
+                                    const Span<MPoly> polys,
+                                    const Span<MLoop> loops,
+                                    const IndexMask mask)
+{
+  /* Use existing normals to avoid unnecessarily recalculating them, if possible. */
+  if (!(mesh.runtime.cd_dirty_poly & CD_MASK_NORMAL) &&
+      CustomData_has_layer(&mesh.pdata, CD_NORMAL)) {
+    const void *data = CustomData_get_layer(&mesh.pdata, CD_NORMAL);
+
+    return std::make_unique<fn::GVArray_For_Span<float3>>(
+        Span<float3>((const float3 *)data, polys.size()));
+  }
+
+  auto normal_fn = [verts, polys, loops](const int i) -> float3 {
+    float3 normal;
+    const MPoly &poly = polys[i];
+    BKE_mesh_calc_poly_normal(&poly, &loops[poly.loopstart], verts.data(), normal);
+    return normal;
+  };
+
+  return std::make_unique<
+      fn::GVArray_For_EmbeddedVArray<float3, VArray_For_Func<float3, decltype(normal_fn)>>>(
+      mask.min_array_size(), mask.min_array_size(), normal_fn);
+}
+
+static GVArrayPtr mesh_vertex_normals(const Mesh &mesh,
+                                      const Span<MVert> verts,
+                                      const Span<MPoly> polys,
+                                      const Span<MLoop> loops,
+                                      const IndexMask mask)
+{
+  /* Use existing normals to avoid unnecessarily recalculating them, if possible. */
+  if (!(mesh.runtime.cd_dirty_vert & CD_MASK_NORMAL) &&
+      CustomData_has_layer(&mesh.vdata, CD_NORMAL)) {
+    const void *data = CustomData_get_layer(&mesh.pdata, CD_NORMAL);
+
+    return std::make_unique<fn::GVArray_For_Span<float3>>(
+        Span<float3>((const float3 *)data, mesh.totvert));
+  }
+
+  /* If the normals are dirty, they must be recalculated for the output of this node's field
+   * source. Ideally vertex normals could be calculated lazily on a const mesh, but that's not
+   * possible at the moment, so we take ownership of the results. Sadly we must also create a copy
+   * of MVert to use the mesh normals API. This can be improved by adding mutex-protected lazy
+   * calculation of normals on meshes.
+   *
+   * Use mask.min_array_size() to avoid calculating a final chunk of data if possible. */
+  Array<MVert> temp_verts(verts);
+  Array<float3> normals(verts.size()); /* Use full size for accumulation from faces. */
+  BKE_mesh_calc_normals_poly_and_vertex(temp_verts.data(),
+                                        mask.min_array_size(),
+                                        loops.data(),
+                                        loops.size(),
+                                        polys.data(),
+                                        polys.size(),
+                                        nullptr,
+                                        (float(*)[3])normals.data());
+
+  return std::make_unique<fn::GVArray_For_ArrayContainer<Array<float3>>>(std::move(normals));
+}
+
+static const GVArray *construct_mesh_normals_gvarray(const MeshComponent &mesh_component,
+                                                     const Mesh &mesh,
+                                                     const IndexMask mask,
+                                                     const AttributeDomain domain,
+                                                     ResourceScope &scope)
+{
+  Span<MVert> verts{mesh.mvert, mesh.totvert};
+  Span<MEdge> edges{mesh.medge, mesh.totedge};
+  Span<MPoly> polys{mesh.mpoly, mesh.totpoly};
+  Span<MLoop> loops{mesh.mloop, mesh.totloop};
+
+  switch (domain) {
+    case ATTR_DOMAIN_FACE: {
+      return scope.add_value(mesh_face_normals(mesh, verts, polys, loops, mask), __func__).get();
+    }
+    case ATTR_DOMAIN_POINT: {
+      return scope.add_value(mesh_vertex_normals(mesh, verts, polys, loops, mask), __func__).get();
+    }
+    case ATTR_DOMAIN_EDGE: {
+      /* In this case, start with vertex normals and convert to the edge domain, since the
+       * conversion from edges to vertices is very simple. Use the full mask since the edges
+       * might use the vertex normal from any index. */
+      GVArrayPtr vert_normals = mesh_vertex_normals(
+          mesh, verts, polys, loops, IndexRange(verts.size()));
+      Span<float3> vert_normals_span = vert_normals->get_internal_span().typed<float3>();
+      Array<float3> edge_normals(mask.min_array_size());
+
+      /* Use "manual" domain interpolation instead of the GeometryComponent API to avoid
+       * calculating unnecessary values and to allow normalizing the result much more simply. */
+      for (const int i : mask) {
+        const MEdge &edge = edges[i];
+        edge_normals[i] = float3::interpolate(
+                              vert_normals_span[edge.v1], vert_normals_span[edge.v2], 0.5f)
+                              .normalized();
+      }
+
+      return &scope.construct<fn::GVArray_For_ArrayContainer<Array<float3>>>(
+          __func__, std::move(edge_normals));
+    }
+    case ATTR_DOMAIN_CORNER: {
+      /* The normals on corners are just the mesh's face normals, so start with the face normal
+       * array and copy the face normal for each of its corners. */
+      GVArrayPtr face_normals = mesh_face_normals(
+          mesh, verts, polys, loops, IndexRange(polys.size()));
+
+      /* In this case using the mesh component's generic domain interpolation is fine, the data
+       * will still be normalized, since the face normal is just copied to every corner. */
+      GVArrayPtr loop_normals = mesh_component.attribute_try_adapt_domain(
+          std::move(face_normals), ATTR_DOMAIN_FACE, ATTR_DOMAIN_CORNER);
+      return scope.add_value(std::move(loop_normals), __func__).get();
+    }
+    default:
+      return nullptr;
+  }
+}
+
+class NormalFieldInput final : public fn::FieldInput {
+ public:
+  NormalFieldInput() : fn::FieldInput(CPPType::get<float3>(), "Normal")
+  {
+  }
+
+  const GVArray *get_varray_for_context(const fn::FieldContext &context,
+                                        IndexMask mask,
+                                        ResourceScope &scope) const final
+  {
+    if (const GeometryComponentFieldContext *geometry_context =
+            dynamic_cast<const GeometryComponentFieldContext *>(&context)) {
+
+      const GeometryComponent &component = geometry_context->geometry_component();
+      const AttributeDomain domain = geometry_context->domain();
+
+      if (component.type() == GEO_COMPONENT_TYPE_MESH) {
+        const MeshComponent &mesh_component = static_cast<const MeshComponent &>(component);
+        const Mesh *mesh = mesh_component.get_for_read();
+        if (mesh == nullptr) {
+          return nullptr;
+        }
+
+        return construct_mesh_normals_gvarray(mesh_component, *mesh, mask, domain, scope);
+      }
+      if (component.type() == GEO_COMPONENT_TYPE_CURVE) {
+        /* TODO: Add curve normals support. */
+        return nullptr;
+      }
+    }
+    return nullptr;
+  }
+
+  uint64_t hash() const override
+  {
+    /* Some random constant hash. */
+    return 669605641;
+  }
+
+  bool is_equal_to(const fn::FieldNode &other) const override
+  {
+    return dynamic_cast<const NormalFieldInput *>(&other) != nullptr;
+  }
+};
+
+static void geo_node_input_normal_exec(GeoNodeExecParams params)
+{
+  Field<float3> normal_field{std::make_shared<NormalFieldInput>()};
+  params.set_output("Normal", std::move(normal_field));
+}
+
+}  // namespace blender::nodes
+
+void register_node_type_geo_input_normal()
+{
+  static bNodeType ntype;
+
+  geo_node_type_base(&ntype, GEO_NODE_INPUT_NORMAL, "Normal", NODE_CLASS_INPUT, 0);
+  ntype.geometry_node_execute = blender::nodes::geo_node_input_normal_exec;
+  ntype.declare = blender::nodes::geo_node_input_normal_declare;
+  nodeRegisterType(&ntype);
+}

source/blender/nodes/geometry/nodes/node_geo_input_position.cc

@@ -0,0 +1,43 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes {
+
+static void geo_node_input_position_declare(NodeDeclarationBuilder &b)
+{
+  b.add_output<decl::Vector>("Position");
+}
+
+static void geo_node_input_position_exec(GeoNodeExecParams params)
+{
+  Field<float3> position_field{
+      std::make_shared<bke::AttributeFieldInput>("position", CPPType::get<float3>())};
+  params.set_output("Position", std::move(position_field));
+}
+
+}  // namespace blender::nodes
+
+void register_node_type_geo_input_position()
+{
+  static bNodeType ntype;
+
+  geo_node_type_base(&ntype, GEO_NODE_INPUT_POSITION, "Position", NODE_CLASS_INPUT, 0);
+  ntype.geometry_node_execute = blender::nodes::geo_node_input_position_exec;
+  ntype.declare = blender::nodes::geo_node_input_position_declare;
+  nodeRegisterType(&ntype);
+}

source/blender/nodes/geometry/nodes/node_geo_join_geometry.cc

@@ -161,34 +161,35 @@ static Array<const GeometryComponent *> to_base_components(Span<const Component
   return components;
 }
 
-static Map<std::string, AttributeMetaData> get_final_attribute_info(
+static Map<AttributeIDRef, AttributeMetaData> get_final_attribute_info(
     Span<const GeometryComponent *> components, Span<StringRef> ignored_attributes)
 {
-  Map<std::string, AttributeMetaData> info;
+  Map<AttributeIDRef, AttributeMetaData> info;
 
   for (const GeometryComponent *component : components) {
-    component->attribute_foreach([&](StringRefNull name, const AttributeMetaData &meta_data) {
-      if (ignored_attributes.contains(name)) {
-        return true;
-      }
-      info.add_or_modify(
-          name,
-          [&](AttributeMetaData *meta_data_final) { *meta_data_final = meta_data; },
-          [&](AttributeMetaData *meta_data_final) {
-            meta_data_final->data_type = blender::bke::attribute_data_type_highest_complexity(
-                {meta_data_final->data_type, meta_data.data_type});
-            meta_data_final->domain = blender::bke::attribute_domain_highest_priority(
-                {meta_data_final->domain, meta_data.domain});
-          });
-      return true;
-    });
+    component->attribute_foreach(
+        [&](const bke::AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+          if (attribute_id.is_named() && ignored_attributes.contains(attribute_id.name())) {
+            return true;
+          }
+          info.add_or_modify(
+              attribute_id,
+              [&](AttributeMetaData *meta_data_final) { *meta_data_final = meta_data; },
+              [&](AttributeMetaData *meta_data_final) {
+                meta_data_final->data_type = blender::bke::attribute_data_type_highest_complexity(
+                    {meta_data_final->data_type, meta_data.data_type});
+                meta_data_final->domain = blender::bke::attribute_domain_highest_priority(
+                    {meta_data_final->domain, meta_data.domain});
+              });
+          return true;
+        });
   }
 
   return info;
 }
 
 static void fill_new_attribute(Span<const GeometryComponent *> src_components,
-                               StringRef attribute_name,
+                               const AttributeIDRef &attribute_id,
                                const CustomDataType data_type,
                                const AttributeDomain domain,
                                GMutableSpan dst_span)
@@ -203,7 +204,7 @@ static void fill_new_attribute(Span<const GeometryComponent *> src_components,
       continue;
     }
     GVArrayPtr read_attribute = component->attribute_get_for_read(
-        attribute_name, domain, data_type, nullptr);
+        attribute_id, domain, data_type, nullptr);
 
     GVArray_GSpan src_span{*read_attribute};
     const void *src_buffer = src_span.data();
@@ -218,20 +219,21 @@ static void join_attributes(Span<const GeometryComponent *> src_components,
                             GeometryComponent &result,
                             Span<StringRef> ignored_attributes = {})
 {
-  const Map<std::string, AttributeMetaData> info = get_final_attribute_info(src_components,
-                                                                            ignored_attributes);
+  const Map<AttributeIDRef, AttributeMetaData> info = get_final_attribute_info(src_components,
+                                                                               ignored_attributes);
 
-  for (const Map<std::string, AttributeMetaData>::Item &item : info.items()) {
-    const StringRef name = item.key;
+  for (const Map<AttributeIDRef, AttributeMetaData>::Item &item : info.items()) {
+    const AttributeIDRef attribute_id = item.key;
     const AttributeMetaData &meta_data = item.value;
 
     OutputAttribute write_attribute = result.attribute_try_get_for_output_only(
-        name, meta_data.domain, meta_data.data_type);
+        attribute_id, meta_data.domain, meta_data.data_type);
     if (!write_attribute) {
       continue;
     }
     GMutableSpan dst_span = write_attribute.as_span();
-    fill_new_attribute(src_components, name, meta_data.data_type, meta_data.domain, dst_span);
+    fill_new_attribute(
+        src_components, attribute_id, meta_data.data_type, meta_data.domain, dst_span);
     write_attribute.save();
   }
 }
@@ -306,7 +308,7 @@ static void join_components(Span<const VolumeComponent *> src_components, Geomet
  * \note This takes advantage of the fact that creating attributes on joined curves never
  * changes a point attribute into a spline attribute; it is always the other way around.
  */
-static void ensure_control_point_attribute(const StringRef name,
+static void ensure_control_point_attribute(const AttributeIDRef &attribute_id,
                                            const CustomDataType data_type,
                                            Span<CurveComponent *> src_components,
                                            CurveEval &result)
@@ -321,7 +323,7 @@ static void ensure_control_point_attribute(const StringRef name,
   const CurveEval *current_curve = src_components[src_component_index]->get_for_read();
 
   for (SplinePtr &spline : splines) {
-    std::optional<GSpan> attribute = spline->attributes.get_for_read(name);
+    std::optional<GSpan> attribute = spline->attributes.get_for_read(attribute_id);
 
     if (attribute) {
       if (attribute->type() != type) {
@@ -334,22 +336,22 @@ static void ensure_control_point_attribute(const StringRef name,
         conversions.try_convert(std::make_unique<GVArray_For_GSpan>(*attribute), type)
             ->materialize(converted_buffer);
 
-        spline->attributes.remove(name);
-        spline->attributes.create_by_move(name, data_type, converted_buffer);
+        spline->attributes.remove(attribute_id);
+        spline->attributes.create_by_move(attribute_id, data_type, converted_buffer);
       }
     }
     else {
-      spline->attributes.create(name, data_type);
+      spline->attributes.create(attribute_id, data_type);
 
-      if (current_curve->attributes.get_for_read(name)) {
+      if (current_curve->attributes.get_for_read(attribute_id)) {
         /* In this case the attribute did not exist, but there is a spline domain attribute
          * we can retrieve a value from, as a spline to point domain conversion. So fill the
          * new attribute with the value for this spline. */
         GVArrayPtr current_curve_attribute = current_curve->attributes.get_for_read(
-            name, data_type, nullptr);
+            attribute_id, data_type, nullptr);
 
-        BLI_assert(spline->attributes.get_for_read(name));
-        std::optional<GMutableSpan> new_attribute = spline->attributes.get_for_write(name);
+        BLI_assert(spline->attributes.get_for_read(attribute_id));
+        std::optional<GMutableSpan> new_attribute = spline->attributes.get_for_write(attribute_id);
 
         BUFFER_FOR_CPP_TYPE_VALUE(type, buffer);
         current_curve_attribute->get(spline_index_in_component, buffer);
@@ -371,15 +373,15 @@ static void ensure_control_point_attribute(const StringRef name,
 /**
  * Fill data for an attribute on the new curve based on all source curves.
  */
-static void ensure_spline_attribute(const StringRef name,
+static void ensure_spline_attribute(const AttributeIDRef &attribute_id,
                                     const CustomDataType data_type,
                                     Span<CurveComponent *> src_components,
                                     CurveEval &result)
 {
   const CPPType &type = *bke::custom_data_type_to_cpp_type(data_type);
 
-  result.attributes.create(name, data_type);
-  GMutableSpan result_attribute = *result.attributes.get_for_write(name);
+  result.attributes.create(attribute_id, data_type);
+  GMutableSpan result_attribute = *result.attributes.get_for_write(attribute_id);
 
   int offset = 0;
   for (const CurveComponent *component : src_components) {
@@ -388,7 +390,7 @@ static void ensure_spline_attribute(const StringRef name,
     if (size == 0) {
       continue;
     }
-    GVArrayPtr read_attribute = curve.attributes.get_for_read(name, data_type, nullptr);
+    GVArrayPtr read_attribute = curve.attributes.get_for_read(attribute_id, data_type, nullptr);
     GVArray_GSpan src_span{*read_attribute};
 
     const void *src_buffer = src_span.data();
@@ -406,19 +408,19 @@ static void ensure_spline_attribute(const StringRef name,
  * \warning Splines have been moved out of the source components at this point, so it
  * is important to only read curve-level data (spline domain attributes) from them.
  */
-static void join_curve_attributes(const Map<std::string, AttributeMetaData> &info,
+static void join_curve_attributes(const Map<AttributeIDRef, AttributeMetaData> &info,
                                   Span<CurveComponent *> src_components,
                                   CurveEval &result)
 {
-  for (const Map<std::string, AttributeMetaData>::Item &item : info.items()) {
-    const StringRef name = item.key;
+  for (const Map<AttributeIDRef, AttributeMetaData>::Item &item : info.items()) {
+    const AttributeIDRef attribute_id = item.key;
     const AttributeMetaData meta_data = item.value;
 
     if (meta_data.domain == ATTR_DOMAIN_CURVE) {
-      ensure_spline_attribute(name, meta_data.data_type, src_components, result);
+      ensure_spline_attribute(attribute_id, meta_data.data_type, src_components, result);
     }
     else {
-      ensure_control_point_attribute(name, meta_data.data_type, src_components, result);
+      ensure_control_point_attribute(attribute_id, meta_data.data_type, src_components, result);
     }
   }
 }
@@ -446,7 +448,7 @@ static void join_curve_components(MutableSpan<GeometrySet> src_geometry_sets, Ge
   }
 
   /* Retrieve attribute info before moving the splines out of the input components. */
-  const Map<std::string, AttributeMetaData> info = get_final_attribute_info(
+  const Map<AttributeIDRef, AttributeMetaData> info = get_final_attribute_info(
       {(const GeometryComponent **)src_components.data(), src_components.size()},
       {"position", "radius", "tilt", "cyclic", "resolution"});
 

source/blender/nodes/geometry/nodes/node_geo_mesh_to_curve.cc

@@ -52,10 +52,10 @@ static void copy_attributes_to_points(CurveEval &curve,
                                       Span<Vector<int>> point_to_vert_maps)
 {
   MutableSpan<SplinePtr> splines = curve.splines();
-  Set<std::string> source_attribute_names = mesh_component.attribute_names();
+  Set<AttributeIDRef> source_attribute_ids = mesh_component.attribute_ids();
 
   /* Copy builtin control point attributes. */
-  if (source_attribute_names.contains_as("tilt")) {
+  if (source_attribute_ids.contains("tilt")) {
     const GVArray_Typed<float> tilt_attribute = mesh_component.attribute_get_for_read<float>(
         "tilt", ATTR_DOMAIN_POINT, 0.0f);
     threading::parallel_for(splines.index_range(), 256, [&](IndexRange range) {
@@ -64,9 +64,9 @@ static void copy_attributes_to_points(CurveEval &curve,
             *tilt_attribute, point_to_vert_maps[i], splines[i]->tilts());
       }
     });
-    source_attribute_names.remove_contained_as("tilt");
+    source_attribute_ids.remove_contained("tilt");
   }
-  if (source_attribute_names.contains_as("radius")) {
+  if (source_attribute_ids.contains("radius")) {
     const GVArray_Typed<float> radius_attribute = mesh_component.attribute_get_for_read<float>(
         "radius", ATTR_DOMAIN_POINT, 1.0f);
     threading::parallel_for(splines.index_range(), 256, [&](IndexRange range) {
@@ -75,15 +75,15 @@ static void copy_attributes_to_points(CurveEval &curve,
             *radius_attribute, point_to_vert_maps[i], splines[i]->radii());
       }
     });
-    source_attribute_names.remove_contained_as("radius");
+    source_attribute_ids.remove_contained("radius");
   }
 
   /* Don't copy other builtin control point attributes. */
-  source_attribute_names.remove_as("position");
+  source_attribute_ids.remove("position");
 
   /* Copy dynamic control point attributes. */
-  for (const StringRef name : source_attribute_names) {
-    const GVArrayPtr mesh_attribute = mesh_component.attribute_try_get_for_read(name,
+  for (const AttributeIDRef &attribute_id : source_attribute_ids) {
+    const GVArrayPtr mesh_attribute = mesh_component.attribute_try_get_for_read(attribute_id,
                                                                                 ATTR_DOMAIN_POINT);
     /* Some attributes might not exist if they were builtin attribute on domains that don't
      * have any elements, i.e. a face attribute on the output of the line primitive node. */
@@ -96,8 +96,9 @@ static void copy_attributes_to_points(CurveEval &curve,
     threading::parallel_for(splines.index_range(), 128, [&](IndexRange range) {
       for (const int i : range) {
         /* Create attribute on the spline points. */
-        splines[i]->attributes.create(name, data_type);
-        std::optional<GMutableSpan> spline_attribute = splines[i]->attributes.get_for_write(name);
+        splines[i]->attributes.create(attribute_id, data_type);
+        std::optional<GMutableSpan> spline_attribute = splines[i]->attributes.get_for_write(
+            attribute_id);
         BLI_assert(spline_attribute);
 
         /* Copy attribute based on the map for this spline. */

source/blender/nodes/geometry/nodes/node_geo_point_distribute.cc

@@ -277,17 +277,17 @@ BLI_NOINLINE static void interpolate_attribute(const Mesh &mesh,
 BLI_NOINLINE static void interpolate_existing_attributes(
     Span<GeometryInstanceGroup> set_groups,
     Span<int> instance_start_offsets,
-    const Map<std::string, AttributeKind> &attributes,
+    const Map<AttributeIDRef, AttributeKind> &attributes,
     GeometryComponent &component,
     Span<Vector<float3>> bary_coords_array,
     Span<Vector<int>> looptri_indices_array)
 {
-  for (Map<std::string, AttributeKind>::Item entry : attributes.items()) {
-    StringRef attribute_name = entry.key;
+  for (Map<AttributeIDRef, AttributeKind>::Item entry : attributes.items()) {
+    const AttributeIDRef attribute_id = entry.key;
     const CustomDataType output_data_type = entry.value.data_type;
     /* The output domain is always #ATTR_DOMAIN_POINT, since we are creating a point cloud. */
     OutputAttribute attribute_out = component.attribute_try_get_for_output_only(
-        attribute_name, ATTR_DOMAIN_POINT, output_data_type);
+        attribute_id, ATTR_DOMAIN_POINT, output_data_type);
     if (!attribute_out) {
       continue;
     }
@@ -301,7 +301,7 @@ BLI_NOINLINE static void interpolate_existing_attributes(
       const Mesh &mesh = *source_component.get_for_read();
 
       std::optional<AttributeMetaData> attribute_info = component.attribute_get_meta_data(
-          attribute_name);
+          attribute_id);
       if (!attribute_info) {
         i_instance += set_group.transforms.size();
         continue;
@@ -309,7 +309,7 @@ BLI_NOINLINE static void interpolate_existing_attributes(
 
       const AttributeDomain source_domain = attribute_info->domain;
       GVArrayPtr source_attribute = source_component.attribute_get_for_read(
-          attribute_name, source_domain, output_data_type, nullptr);
+          attribute_id, source_domain, output_data_type, nullptr);
       if (!source_attribute) {
         i_instance += set_group.transforms.size();
         continue;
@@ -406,7 +406,7 @@ BLI_NOINLINE static void compute_special_attributes(Span<GeometryInstanceGroup>
 BLI_NOINLINE static void add_remaining_point_attributes(
     Span<GeometryInstanceGroup> set_groups,
     Span<int> instance_start_offsets,
-    const Map<std::string, AttributeKind> &attributes,
+    const Map<AttributeIDRef, AttributeKind> &attributes,
     GeometryComponent &component,
     Span<Vector<float3>> bary_coords_array,
     Span<Vector<int>> looptri_indices_array)
@@ -629,7 +629,7 @@ static void geo_node_point_distribute_exec(GeoNodeExecParams params)
   PointCloudComponent &point_component =
       geometry_set_out.get_component_for_write<PointCloudComponent>();
 
-  Map<std::string, AttributeKind> attributes;
+  Map<AttributeIDRef, AttributeKind> attributes;
   bke::geometry_set_gather_instances_attribute_info(
       set_groups, {GEO_COMPONENT_TYPE_MESH}, {"position", "normal", "id"}, attributes);
   add_remaining_point_attributes(set_groups,

source/blender/nodes/geometry/nodes/node_geo_point_separate.cc

@@ -53,8 +53,8 @@ void copy_point_attributes_based_on_mask(const GeometryComponent &in_component,
                                          Span<bool> masks,
                                          const bool invert)
 {
-  for (const std::string &name : in_component.attribute_names()) {
-    ReadAttributeLookup attribute = in_component.attribute_try_get_for_read(name);
+  for (const AttributeIDRef &attribute_id : in_component.attribute_ids()) {
+    ReadAttributeLookup attribute = in_component.attribute_try_get_for_read(attribute_id);
     const CustomDataType data_type = bke::cpp_type_to_custom_data_type(attribute.varray->type());
 
     /* Only copy point attributes. Theoretically this could interpolate attributes on other
@@ -65,7 +65,7 @@ void copy_point_attributes_based_on_mask(const GeometryComponent &in_component,
     }
 
     OutputAttribute result_attribute = result_component.attribute_try_get_for_output_only(
-        name, ATTR_DOMAIN_POINT, data_type);
+        attribute_id, ATTR_DOMAIN_POINT, data_type);
 
     attribute_math::convert_to_static_type(data_type, [&](auto dummy) {
       using T = decltype(dummy);

source/blender/nodes/geometry/nodes/node_geo_set_position.cc

@@ -0,0 +1,79 @@
+/*
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ */
+
+#include "DEG_depsgraph_query.h"
+
+#include "node_geometry_util.hh"
+
+namespace blender::nodes {
+
+static void geo_node_set_position_declare(NodeDeclarationBuilder &b)
+{
+  b.add_input<decl::Geometry>("Geometry");
+  b.add_input<decl::Vector>("Position");
+  b.add_input<decl::Bool>("Selection").default_value(true);
+  b.add_output<decl::Geometry>("Geometry");
+}
+
+static void set_position_in_component(GeometryComponent &component,
+                                      const Field<bool> &selection_field,
+                                      const Field<float3> &position_field)
+{
+  GeometryComponentFieldContext field_context{component, ATTR_DOMAIN_POINT};
+  const int domain_size = component.attribute_domain_size(ATTR_DOMAIN_POINT);
+
+  fn::FieldEvaluator selection_evaluator{field_context, domain_size};
+  selection_evaluator.add(selection_field);
+  selection_evaluator.evaluate();
+  const IndexMask selection = selection_evaluator.get_evaluated_as_mask(0);
+
+  OutputAttribute_Typed<float3> positions = component.attribute_try_get_for_output<float3>(
+      "position", ATTR_DOMAIN_POINT, {0, 0, 0});
+  fn::FieldEvaluator position_evaluator{field_context, &selection};
+  position_evaluator.add_with_destination(position_field, positions.varray());
+  position_evaluator.evaluate();
+  positions.save();
+}
+
+static void geo_node_set_position_exec(GeoNodeExecParams params)
+{
+  GeometrySet geometry = params.extract_input<GeometrySet>("Geometry");
+  geometry = geometry_set_realize_instances(geometry);
+  Field<bool> selection_field = params.extract_input<Field<bool>>("Selection");
+  Field<float3> position_field = params.extract_input<Field<float3>>("Position");
+
+  for (const GeometryComponentType type :
+       {GEO_COMPONENT_TYPE_MESH, GEO_COMPONENT_TYPE_POINT_CLOUD, GEO_COMPONENT_TYPE_CURVE}) {
+    if (geometry.has(type)) {
+      set_position_in_component(
+          geometry.get_component_for_write(type), selection_field, position_field);
+    }
+  }
+
+  params.set_output("Geometry", std::move(geometry));
+}
+
+}  // namespace blender::nodes
+
+void register_node_type_geo_set_position()
+{
+  static bNodeType ntype;
+
+  geo_node_type_base(&ntype, GEO_NODE_SET_POSITION, "Set Position", NODE_CLASS_GEOMETRY, 0);
+  ntype.geometry_node_execute = blender::nodes::geo_node_set_position_exec;
+  ntype.declare = blender::nodes::geo_node_set_position_declare;
+  nodeRegisterType(&ntype);
+}

source/blender/nodes/intern/geometry_nodes_eval_log.cc

@@ -161,8 +161,10 @@ GeometryValueLog::GeometryValueLog(const GeometrySet &geometry_set, bool log_ful
 {
   bke::geometry_set_instances_attribute_foreach(
       geometry_set,
-      [&](StringRefNull attribute_name, const AttributeMetaData &meta_data) {
-        this->attributes_.append({attribute_name, meta_data.domain, meta_data.data_type});
+      [&](const bke::AttributeIDRef &attribute_id, const AttributeMetaData &meta_data) {
+        if (attribute_id.is_named()) {
+          this->attributes_.append({attribute_id.name(), meta_data.domain, meta_data.data_type});
+        }
         return true;
       },
       8);

source/blender/nodes/intern/node_socket.cc

@@ -48,6 +48,7 @@
 #include "NOD_socket.h"
 
 #include "FN_cpp_type_make.hh"
+#include "FN_field.hh"
 
 using namespace blender;
 using blender::nodes::SocketDeclarationPtr;
@@ -701,8 +702,14 @@ static bNodeSocketType *make_socket_type_bool()
   socktype->get_base_cpp_value = [](const bNodeSocket &socket, void *r_value) {
     *(bool *)r_value = ((bNodeSocketValueBoolean *)socket.default_value)->value;
   };
-  socktype->get_geometry_nodes_cpp_type = socktype->get_base_cpp_type;
-  socktype->get_geometry_nodes_cpp_value = socktype->get_base_cpp_value;
+  socktype->get_geometry_nodes_cpp_type = []() {
+    return &blender::fn::CPPType::get<blender::fn::Field<bool>>();
+  };
+  socktype->get_geometry_nodes_cpp_value = [](const bNodeSocket &socket, void *r_value) {
+    bool value;
+    socket.typeinfo->get_base_cpp_value(socket, &value);
+    new (r_value) blender::fn::Field<bool>(blender::fn::make_constant_field(value));
+  };
   return socktype;
 }
 
@@ -713,8 +720,14 @@ static bNodeSocketType *make_socket_type_float(PropertySubType subtype)
   socktype->get_base_cpp_value = [](const bNodeSocket &socket, void *r_value) {
     *(float *)r_value = ((bNodeSocketValueFloat *)socket.default_value)->value;
   };
-  socktype->get_geometry_nodes_cpp_type = socktype->get_base_cpp_type;
-  socktype->get_geometry_nodes_cpp_value = socktype->get_base_cpp_value;
+  socktype->get_geometry_nodes_cpp_type = []() {
+    return &blender::fn::CPPType::get<blender::fn::Field<float>>();
+  };
+  socktype->get_geometry_nodes_cpp_value = [](const bNodeSocket &socket, void *r_value) {
+    float value;
+    socket.typeinfo->get_base_cpp_value(socket, &value);
+    new (r_value) blender::fn::Field<float>(blender::fn::make_constant_field(value));
+  };
   return socktype;
 }
 
@@ -725,8 +738,14 @@ static bNodeSocketType *make_socket_type_int(PropertySubType subtype)
   socktype->get_base_cpp_value = [](const bNodeSocket &socket, void *r_value) {
     *(int *)r_value = ((bNodeSocketValueInt *)socket.default_value)->value;
   };
-  socktype->get_geometry_nodes_cpp_type = socktype->get_base_cpp_type;
-  socktype->get_geometry_nodes_cpp_value = socktype->get_base_cpp_value;
+  socktype->get_geometry_nodes_cpp_type = []() {
+    return &blender::fn::CPPType::get<blender::fn::Field<int>>();
+  };
+  socktype->get_geometry_nodes_cpp_value = [](const bNodeSocket &socket, void *r_value) {
+    int value;
+    socket.typeinfo->get_base_cpp_value(socket, &value);
+    new (r_value) blender::fn::Field<int>(blender::fn::make_constant_field(value));
+  };
   return socktype;
 }
 
@@ -737,8 +756,14 @@ static bNodeSocketType *make_socket_type_vector(PropertySubType subtype)
   socktype->get_base_cpp_value = [](const bNodeSocket &socket, void *r_value) {
     *(blender::float3 *)r_value = ((bNodeSocketValueVector *)socket.default_value)->value;
   };
-  socktype->get_geometry_nodes_cpp_type = socktype->get_base_cpp_type;
-  socktype->get_geometry_nodes_cpp_value = socktype->get_base_cpp_value;
+  socktype->get_geometry_nodes_cpp_type = []() {
+    return &blender::fn::CPPType::get<blender::fn::Field<blender::float3>>();
+  };
+  socktype->get_geometry_nodes_cpp_value = [](const bNodeSocket &socket, void *r_value) {
+    blender::float3 value;
+    socket.typeinfo->get_base_cpp_value(socket, &value);
+    new (r_value) blender::fn::Field<blender::float3>(blender::fn::make_constant_field(value));
+  };
   return socktype;
 }
 
@@ -751,8 +776,15 @@ static bNodeSocketType *make_socket_type_rgba()
   socktype->get_base_cpp_value = [](const bNodeSocket &socket, void *r_value) {
     *(blender::ColorGeometry4f *)r_value = ((bNodeSocketValueRGBA *)socket.default_value)->value;
   };
-  socktype->get_geometry_nodes_cpp_type = socktype->get_base_cpp_type;
-  socktype->get_geometry_nodes_cpp_value = socktype->get_base_cpp_value;
+  socktype->get_geometry_nodes_cpp_type = []() {
+    return &blender::fn::CPPType::get<blender::fn::Field<blender::ColorGeometry4f>>();
+  };
+  socktype->get_geometry_nodes_cpp_value = [](const bNodeSocket &socket, void *r_value) {
+    blender::ColorGeometry4f value;
+    socket.typeinfo->get_base_cpp_value(socket, &value);
+    new (r_value)
+        blender::fn::Field<blender::ColorGeometry4f>(blender::fn::make_constant_field(value));
+  };
   return socktype;
 }
 
@@ -763,8 +795,15 @@ static bNodeSocketType *make_socket_type_string()
   socktype->get_base_cpp_value = [](const bNodeSocket &socket, void *r_value) {
     new (r_value) std::string(((bNodeSocketValueString *)socket.default_value)->value);
   };
-  socktype->get_geometry_nodes_cpp_type = socktype->get_base_cpp_type;
-  socktype->get_geometry_nodes_cpp_value = socktype->get_base_cpp_value;
+  socktype->get_geometry_nodes_cpp_type = []() {
+    return &blender::fn::CPPType::get<blender::fn::Field<std::string>>();
+  };
+  socktype->get_geometry_nodes_cpp_value = [](const bNodeSocket &socket, void *r_value) {
+    std::string value;
+    value.~basic_string();
+    socket.typeinfo->get_base_cpp_value(socket, &value);
+    new (r_value) blender::fn::Field<std::string>(blender::fn::make_constant_field(value));
+  };
   return socktype;
 }