source/blender/blenkernel/BKE_volume_attribute.hh

@@ -62,7 +62,7 @@ template<typename T> struct AttributeGridWriter {
   /**
    * Grid pointer giving read and write access to the attribute. This may be empty.
    */
-  volume::Grid<T> grid;
+  volume::MutableGrid<T> grid;
   /**
    * Domain where the attribute is stored on the geometry. Also determines the size of the
    * virtual array.
@@ -121,7 +121,7 @@ struct GAttributeGridReader {
  * A generic version of #AttributeWriter.
  */
 struct GAttributeGridWriter {
-  volume::GGrid &grid;
+  volume::GMutableGrid &grid;
   eAttrDomain domain;
   std::function<void()> tag_modified_fn;
 

source/blender/blenkernel/intern/geometry_fields.cc

@@ -571,14 +571,14 @@ bool try_capture_field_on_geometry(GeometryComponent &component,
     }
     if (GAttributeGridWriter dst_attribute = attributes.lookup_grid_for_write(attribute_id)) {
       const bke::GeometryFieldContext field_context{component, domain};
-      fn::VolumeFieldEvaluator evaluator{field_context, domain_size};
+      fn::VolumeFieldEvaluator evaluator{field_context};
       evaluator.add(validator.validate_field_if_necessary(field));
       evaluator.set_selection(selection);
       evaluator.evaluate();
 
-      const IndexMask selection = evaluator.get_evaluated_selection_as_mask();
+      const volume::GridMask selection = evaluator.get_evaluated_selection_as_mask();
 
-      array_utils::copy(evaluator.get_evaluated(0), selection, dst_attribute.span);
+      dst_attribute.grid.try_copy_masked(evaluator.get_evaluated(0), selection);
 
       dst_attribute.finish();
       return true;

source/blender/blenlib/BLI_volume.hh

@@ -145,7 +145,9 @@ class GridMask {
   GridMask(const GridMask &other) = default;
   GridMask &operator=(const GridMask &other)
   {
+#ifdef WITH_OPENVDB
     grid_ = other.grid_;
+#endif
     return *this;
   }
 
@@ -197,7 +199,9 @@ class GMutableGrid {
 
   operator GGrid() const
   {
-    return {grid_};
+#ifdef WITH_OPENVDB
+    return GGrid{grid_};
+#endif
   }
 
   /* Create an empty grid with a background value. */
@@ -213,7 +217,8 @@ class GMutableGrid {
                              const void *inactive_value,
                              const void *active_value);
 
-  bool try_assign(const GMutableGrid &other);
+  bool try_assign(const GGrid &other);
+  bool try_copy_masked(const GGrid &other, const GridMask &selection);
 
   int64_t voxel_count() const;
   bool is_empty() const;

source/blender/blenlib/intern/volume.cc

@@ -20,6 +20,8 @@ const openvdb::MaskGrid::ConstPtr empty_grid_ = openvdb::MaskGrid::create();
 GridMask GridMask::from_bools(const volume::GridMask &full_mask,
                               const volume::Grid<bool> &selection)
 {
+  BLI_assert_unreachable();
+  return {};
 }
 
 bool GridMask::is_empty() const
@@ -110,6 +112,16 @@ GMutableGrid GMutableGrid::create(ResourceScope &scope,
   return GMutableGrid{scope.add_value<openvdb::GridBase::Ptr>(std::move(grid))};
 }
 
+bool GMutableGrid::try_assign(const GGrid & /*other*/)
+{
+  return false;
+}
+
+bool GMutableGrid::try_copy_masked(const GGrid & /*other*/, const GridMask & /*mask*/)
+{
+  return false;
+}
+
 template<typename T>
 MutableGrid<T> MutableGrid<T>::create(ResourceScope &scope, const T &background_value)
 {
@@ -214,11 +226,6 @@ GGrid GGrid::create(ResourceScope & /*scope*/,
   return GGrid{};
 }
 
-bool GGrid::try_assign(const GGrid &other)
-{
-  return false;
-}
-
 template<typename T>
 Grid<T> Grid<T>::create(ResourceScope & /*scope*/, const T & /*background_value*/)
 {

source/blender/functions/FN_field.hh

@@ -178,8 +178,7 @@ class GFieldRef : public GFieldBase<const FieldNode *> {
 
 namespace detail {
 /* Utility class to make #is_field_v work. */
-struct TypedFieldBase {
-};
+struct TypedFieldBase {};
 }  // namespace detail
 
 /**
@@ -525,6 +524,8 @@ class VolumeFieldEvaluator : NonMovable, NonCopyable {
   {
   }
 
+  VolumeFieldEvaluator(const FieldContext &context) : context_(context), mask_(GridMask()) {}
+
   ~VolumeFieldEvaluator()
   {
     /* While this assert isn't strictly necessary, and could be replaced with a warning,