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, 103 insertions, 0 deletions

diff --git a/source/blender/blenkernel/intern/geometry_set.cc b/source/blender/blenkernel/intern/geometry_set.cc
index 81958b81213..7a3239babd4 100644
--- a/source/blender/blenkernel/intern/geometry_set.cc
+++ b/source/blender/blenkernel/intern/geometry_set.cc
@@ -19,6 +19,7 @@
 #include "BKE_mesh.h"
 #include "BKE_mesh_wrapper.h"
 #include "BKE_pointcloud.h"
+#include "BKE_volume.h"
 
 #include "DNA_object_types.h"
 
@@ -51,6 +52,8 @@ GeometryComponent *GeometryComponent::create(GeometryComponentType component_typ
       return new PointCloudComponent();
     case GeometryComponentType::Instances:
       return new InstancesComponent();
+    case GeometryComponentType::Volume:
+      return new VolumeComponent();
   }
   BLI_assert(false);
   return nullptr;
@@ -201,6 +204,13 @@ const PointCloud *GeometrySet::get_pointcloud_for_read() const
   return (component == nullptr) ? nullptr : component->get_for_read();
 }
 
+/* Returns a read-only volume or null. */
+const Volume *GeometrySet::get_volume_for_read() const
+{
+  const VolumeComponent *component = this->get_component_for_read<VolumeComponent>();
+  return (component == nullptr) ? nullptr : component->get_for_read();
+}
+
 /* Returns true when the geometry set has a point cloud component that has a point cloud. */
 bool GeometrySet::has_pointcloud() const
 {
@@ -215,6 +225,13 @@ bool GeometrySet::has_instances() const
   return component != nullptr && component->instances_amount() >= 1;
 }
 
+/* Returns true when the geometry set has a volume component that has a volume. */
+bool GeometrySet::has_volume() const
+{
+  const VolumeComponent *component = this->get_component_for_read<VolumeComponent>();
+  return component != nullptr && component->has_volume();
+}
+
 /* Create a new geometry set that only contains the given mesh. */
 GeometrySet GeometrySet::create_with_mesh(Mesh *mesh, GeometryOwnershipType ownership)
 {
@@ -262,6 +279,13 @@ PointCloud *GeometrySet::get_pointcloud_for_write()
   return component.get_for_write();
 }
 
+/* Returns a mutable volume or null. No ownership is transferred. */
+Volume *GeometrySet::get_volume_for_write()
+{
+  VolumeComponent &component = this->get_component_for_write<VolumeComponent>();
+  return component.get_for_write();
+}
+
 /** \} */
 
 /* -------------------------------------------------------------------- */
@@ -567,6 +591,85 @@ bool InstancesComponent::is_empty() const
 /** \} */
 
 /* -------------------------------------------------------------------- */
+/** \name Volume Component
+ * \{ */
+
+VolumeComponent::VolumeComponent() : GeometryComponent(GeometryComponentType::Volume)
+{
+}
+
+VolumeComponent::~VolumeComponent()
+{
+  this->clear();
+}
+
+GeometryComponent *VolumeComponent::copy() const
+{
+  VolumeComponent *new_component = new VolumeComponent();
+  if (volume_ != nullptr) {
+    new_component->volume_ = BKE_volume_copy_for_eval(volume_, false);
+    new_component->ownership_ = GeometryOwnershipType::Owned;
+  }
+  return new_component;
+}
+
+void VolumeComponent::clear()
+{
+  BLI_assert(this->is_mutable());
+  if (volume_ != nullptr) {
+    if (ownership_ == GeometryOwnershipType::Owned) {
+      BKE_id_free(nullptr, volume_);
+    }
+    volume_ = nullptr;
+  }
+}
+
+bool VolumeComponent::has_volume() const
+{
+  return volume_ != nullptr;
+}
+
+/* Clear the component and replace it with the new volume. */
+void VolumeComponent::replace(Volume *volume, GeometryOwnershipType ownership)
+{
+  BLI_assert(this->is_mutable());
+  this->clear();
+  volume_ = volume;
+  ownership_ = ownership;
+}
+
+/* Return the volume and clear the component. The caller takes over responsibility for freeing the
+ * volume (if the component was responsible before). */
+Volume *VolumeComponent::release()
+{
+  BLI_assert(this->is_mutable());
+  Volume *volume = volume_;
+  volume_ = nullptr;
+  return volume;
+}
+
+/* Get the volume from this component. This method can be used by multiple threads at the same
+ * time. Therefore, the returned volume should not be modified. No ownership is transferred. */
+const Volume *VolumeComponent::get_for_read() const
+{
+  return volume_;
+}
+
+/* Get the volume from this component. This method can only be used when the component is mutable,
+ * i.e. it is not shared. The returned volume can be modified. No ownership is transferred. */
+Volume *VolumeComponent::get_for_write()
+{
+  BLI_assert(this->is_mutable());
+  if (ownership_ == GeometryOwnershipType::ReadOnly) {
+    volume_ = BKE_volume_copy_for_eval(volume_, false);
+    ownership_ = GeometryOwnershipType::Owned;
+  }
+  return volume_;
+}
+
+/** \} */
+
+/* -------------------------------------------------------------------- */
 /** \name C API
  * \{ */