Utility BKE header for forward-declaring OpenVDB grid types.

The socket value will be extended from ValueOrField to
"ValueOrFieldOrGrid" (with a nicer name). The data type is the same,
and the socket shape will be updated later when inferencing supports
grid data.

@@ -0,0 +59,4 @@
+};
+
+template<typename FieldValueType, typename GridValueType, typename LeafBufferValueType>
+struct GridConverter_CopyConstruct {

@@ -0,0 +275,4 @@
+
+namespace grid_utils {
+
+template<typename T> bool get_background_value(const VolumeGridPtr<T> &grid, T &r_value)

@@ -0,0 +8,4 @@
+ * \ingroup bli
+ */
+
+enum VolumeGridType : int8_t {

@@ -412,6 +415,7 @@ DefNode(GeometryNode, GEO_NODE_RESAMPLE_CURVE, 0, "RESAMPLE_CURVE", ResampleCurv
 DefNode(GeometryNode, GEO_NODE_REVERSE_CURVE, 0, "REVERSE_CURVE", ReverseCurve, "Reverse Curve", "Change the direction of curves by swapping their start and end data")
 DefNode(GeometryNode, GEO_NODE_ROTATE_INSTANCES, 0, "ROTATE_INSTANCES", RotateInstances, "Rotate Instances", "Rotate geometry instances in local or global space")
 DefNode(GeometryNode, GEO_NODE_SAMPLE_CURVE, def_geo_curve_sample, "SAMPLE_CURVE", SampleCurve, "Sample Curve", "Retrieve data from a point on a curve at a certain distance from its start")
+DefNode(GeometryNode, GEO_NODE_SAMPLE_GRID, 0, "SAMPLE_GRID", SampleGrid, "Sample Grid", "Sample a volume grid value")

@@ -51,2 +70,4 @@
       return fn::evaluate_constant_field(this->field);
     }
+    if (this->grid) {
+      /* Returns the grid background value. */

@@ -73,2 +80,2 @@
-VolumeGrid *BKE_volume_grid_get_for_write(Volume *volume, int grid_index);
-const VolumeGrid *BKE_volume_grid_active_get_for_read(const Volume *volume);
+GVolumeGridPtr BKE_volume_grid_get_for_read(const Volume *volume, int grid_index);
+GVolumeGridPtr BKE_volume_grid_get_for_write(Volume *volume, int grid_index);

@@ -0,0 +45,4 @@
+ * Procedurally generated grids are not.
+ * \{ */
+
+struct GVolumeGridPtr : public VolumeGridPtrCommon {

@@ -0,0 +72,4 @@
+    }
+  }
+
+  params.set_default_remaining_outputs();

@@ -0,0 +27,4 @@
+
+  b.add_input<decl::Geometry>("Volume");
+  b.add_input<decl::String>("Name");
+  grids::declare_grid_type_input(b, eCustomDataType(node->custom1), "Grid");

@@ -0,0 +68,4 @@
+  if (volume) {
+    bke::GVolumeGridPtr grid = grids::extract_grid_input(params, "Grid", data_type);
+    if (!grid) {
+      return;

@@ -0,0 +82,4 @@
+    return;
+  }
+
+  params.set_default_remaining_outputs();

@@ -0,0 +9,4 @@
+ */
+
+#include <mutex>
+#include <unordered_set>

@@ -0,0 +39,4 @@
+#ifdef WITH_OPENVDB
+namespace grids {
+
+template<typename T> struct AttributeConverter {

@@ -0,0 +147,4 @@
+  VolumeGrid(const char *template_file_path,
+             const GridBasePtr &template_grid,
+             int simplify_level = 0);
+  VolumeGrid(const VolumeGrid &other);

@@ -0,0 +150,4 @@
+  VolumeGrid(const VolumeGrid &other);
+  ~VolumeGrid();
+
+  const char *name() const;

@@ -0,0 +152,4 @@
+
+  const char *name() const;
+
+  const char *error_message() const;

@@ -0,0 +156,4 @@
+
+  bool grid_is_loaded() const;
+
+  void load(const char *volume_name, const char *filepath) const;

@@ -0,0 +161,4 @@
+
+  void set_simplify_level(int simplify_level);
+
+  void clear_reference(const char *volume_name);

@@ -0,0 +23,4 @@
+/* -------------------------------------------------------------------- */
+/** \name Common Grid Wrapper
+ *
+ * Base class for both generic and typed grid wrapper classes.

@@ -0,0 +28,4 @@
+
+struct VolumeGridPtrCommon : ImplicitSharingPtr<VolumeGrid> {
+#ifdef WITH_OPENVDB
+  using GridPtr = std::shared_ptr<openvdb::GridBase>;

@@ -0,0 +37,4 @@
+  /* Enable implicit conversion from nullptr. */
+  VolumeGridPtrCommon(std::nullptr_t) : ImplicitSharingPtr<VolumeGrid>(nullptr) {}
+  using ImplicitSharingPtr<VolumeGrid>::ImplicitSharingPtr;
+  virtual ~VolumeGridPtrCommon();

@@ -0,0 +45,4 @@
+/* -------------------------------------------------------------------- */
+/** \name Generic Volume Grid
+ *
+ * Wrapper around a generic OpenVDB grid.

@@ -0,0 +46,4 @@
+/** \name Generic Volume Grid
+ *
+ * Wrapper around a generic OpenVDB grid.
+ * Grids loaded from OpenVDB files are always stored in the global cache.

@@ -0,0 +142,4 @@
+};
+/* Stub class for string attributes, not supported. */
+template<> struct VolumeGridTraits<std::string> {
+  using TreeType = openvdb::MaskTree;

@@ -0,0 +159,4 @@
+  using GridPtr = std::shared_ptr<GridType>;
+  using GridConstPtr = std::shared_ptr<const GridType>;
+
+  VolumeGridPtr(const GVolumeGridPtr &other) : VolumeGridPtrCommon(other.get()) {}

@@ -0,0 +170,4 @@
+  GridPtr grid_for_write() const
+  {
+    const VolumeGrid *data = this->get();
+    if (data->is_mutable()) {

@@ -0,0 +173,4 @@
+    if (data->is_mutable()) {
+      return openvdb::GridBase::grid<GridType>(const_cast<VolumeGrid *>(data)->grid_for_write());
+    }
+    return openvdb::GridBase::grid<GridType>(data->grid()->deepCopyGrid());

@@ -0,0 +203,4 @@
+template<typename T> std::optional<T> get_background_value(const VolumeGridPtr<T> &grid)
+{
+#ifdef WITH_OPENVDB
+  if constexpr (std::is_same_v<T, std::string>) {

@@ -1241,2 +860,3 @@
+  for (GVolumeGridPtr &grid : grids) {
     if (grid_index-- == 0) {
-      return &grid;
+      return const_cast<VolumeGrid *>(grid.get());

@@ -133,2 +134,4 @@
 };
 
+template<typename T, typename... Args>
+inline ImplicitSharingPtr<T> make_implicit_shared(Args &&...args)

@@ -0,0 +69,4 @@
+      params.set_output("Volume", geometry_set);
+
+      if (remove_grid) {
+        BKE_volume_grid_remove(volume, grid);

@@ -0,0 +75,4 @@
+    }
+  }
+
+  grids::set_output_grid(params, "Grid", data_type, nullptr);

@@ -158,6 +158,10 @@ static void transform_volume(GeoNodeExecParams &params,
   const int grids_num = BKE_volume_num_grids(&volume);
   for (const int i : IndexRange(grids_num)) {
     VolumeGrid *volume_grid = BKE_volume_grid_get_for_write(&volume, i);
+    if (!volume_grid->is_mutable()) {

@@ -0,0 +66,4 @@
+  }
+
+#ifdef WITH_OPENVDB
+  GridConstPtr grid() const;

@@ -0,0 +142,4 @@
+  /* Source of the tree data stored in the grid. */
+  VolumeTreeSource tree_source() const;
+  /* Make sure the tree data has been loaded if the grid has a file source. */
+  bool ensure_tree_loaded(

@@ -0,0 +145,4 @@
+  bool ensure_tree_loaded(
+      StringRef filepath, FunctionRef<void(StringRef)> error_fn = [](StringRef) {}) const;
+  /* Unload the tree data but keep metadata. */
+  void unload_tree() const;

@@ -0,0 +148,4 @@
+  void unload_tree() const;
+
+ protected:
+  GridBasePtr main_grid() const;

@@ -0,0 +20,4 @@
+
+bool VolumeFileCache::has_grid(const VolumeFileCacheKey &key) const
+{
+  return file_grids_.contains(key);

@@ -0,0 +48,4 @@
+}
+
+/* Returns the original grid or a simplified version depending on the given #simplify_level. */
+GVolumeGridPtr VolumeFileCache::get_simplified_grid(const VolumeFileCacheKey &key,

@@ -332,6 +332,7 @@ DefNode(GeometryNode, GEO_NODE_FILL_CURVE, 0, "FILL_CURVE", FillCurve, "Fill Cur
 DefNode(GeometryNode, GEO_NODE_FILLET_CURVE, 0, "FILLET_CURVE", FilletCurve, "Fillet Curve", "Round corners by generating circular arcs on each control point")
 DefNode(GeometryNode, GEO_NODE_FLIP_FACES, 0, "FLIP_FACES", FlipFaces, "Flip Faces", "Reverse the order of the vertices and edges of selected faces, flipping their normal direction")
 DefNode(GeometryNode, GEO_NODE_GEOMETRY_TO_INSTANCE, 0, "GEOMETRY_TO_INSTANCE", GeometryToInstance, "Geometry to Instance", "Convert each input geometry into an instance, which can be much faster than the Join Geometry node when the inputs are large")
+DefNode(GeometryNode, GEO_NODE_GET_NAMED_GRID, 0, "GET_NAMED_GRID", GetNamedGrid, "Get Named Grid", "Get grid data from a volume geometry with the specified name")

@@ -0,0 +55,4 @@
+
+static void try_store_grid(GeoNodeExecParams params, Volume *volume)
+{
+  BLI_assert(volume);