Geometry Nodes: initial support for volumes

For the most part, this just adds boilerplate code for volume support in geometry nodes:
* Add `VolumeComponent` next to `MeshComponent`, etc.
* Support `VolumeComponent` in depsgraph object iterator.

Furthermore, I added initial volume support in a few nodes:
* The Object Info node outputs an object instance when the input is a volume object
  (that will be the same for mesh objects soonish, to avoid copies).
* Support transforming a `VolumeComponent` in the Transform node.
* Support the `VolumeComponent` in Join Geometry nodes, but only when just one of the
  inputs has a volume component for now.

Right now, there is no way to create a `VolumeComponent`, because the Object Info node
outputs an object instance. The `VolumeComponent` will be necessary for upcoming nodes,
which will generate volumes on the fly.

Viewport selection does not work correctly with `VolumeComponent`s currently. I don't
know why that is. That can be figured out a bit later, once we can actually create
new volumes in geometry nodes.

Ref T84604.

Differential Revision: https://developer.blender.org/D10147

1 files changed, 27 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_geometry_set.hh b/source/blender/blenkernel/BKE_geometry_set.hh
index ad5a5d57045..adc08f699fd 100644
--- a/source/blender/blenkernel/BKE_geometry_set.hh
+++ b/source/blender/blenkernel/BKE_geometry_set.hh
@@ -36,6 +36,7 @@ struct Collection;
 struct Mesh;
 struct Object;
 struct PointCloud;
+struct Volume;
 
 /* Each geometry component has a specific type. The type determines what kind of data the component
  * stores. Functions modifying a geometry will usually just modify a subset of the component types.
@@ -44,6 +45,7 @@ enum class GeometryComponentType {
   Mesh = 0,
   PointCloud = 1,
   Instances = 2,
+  Volume = 3,
 };
 
 enum class GeometryOwnershipType {
@@ -319,10 +321,13 @@ struct GeometrySet {
   bool has_mesh() const;
   bool has_pointcloud() const;
   bool has_instances() const;
+  bool has_volume() const;
   const Mesh *get_mesh_for_read() const;
   const PointCloud *get_pointcloud_for_read() const;
+  const Volume *get_volume_for_read() const;
   Mesh *get_mesh_for_write();
   PointCloud *get_pointcloud_for_write();
+  Volume *get_volume_for_write();
 
   /* Utility methods for replacement. */
   void replace_mesh(Mesh *mesh, GeometryOwnershipType ownership = GeometryOwnershipType::Owned);
@@ -464,3 +469,25 @@ class InstancesComponent : public GeometryComponent {
 
   static constexpr inline GeometryComponentType static_type = GeometryComponentType::Instances;
 };
+
+/** A geometry component that stores volume grids. */
+class VolumeComponent : public GeometryComponent {
+ private:
+  Volume *volume_ = nullptr;
+  GeometryOwnershipType ownership_ = GeometryOwnershipType::Owned;
+
+ public:
+  VolumeComponent();
+  ~VolumeComponent();
+  GeometryComponent *copy() const override;
+
+  void clear();
+  bool has_volume() const;
+  void replace(Volume *volume, GeometryOwnershipType ownership = GeometryOwnershipType::Owned);
+  Volume *release();
+
+  const Volume *get_for_read() const;
+  Volume *get_for_write();
+
+  static constexpr inline GeometryComponentType static_type = GeometryComponentType::Volume;
+};