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

4 files changed, 77 insertions, 0 deletions

diff --git a/source/blender/nodes/CMakeLists.txt b/source/blender/nodes/CMakeLists.txt
index ed4d658eb4f..9057e4c6be8 100644
--- a/source/blender/nodes/CMakeLists.txt
+++ b/source/blender/nodes/CMakeLists.txt
@@ -366,4 +366,11 @@ if(WITH_OPENSUBDIV)
   add_definitions(-DWITH_OPENSUBDIV)
 endif()
 
+if(WITH_OPENVDB)
+  list(APPEND INC_SYS
+    ${OPENVDB_INCLUDE_DIRS}
+  )
+  add_definitions(-DWITH_OPENVDB ${OPENVDB_DEFINITIONS})
+endif()
+
 blender_add_lib(bf_nodes "${SRC}" "${INC}" "${INC_SYS}" "${LIB}")
diff --git a/source/blender/nodes/geometry/nodes/node_geo_join_geometry.cc b/source/blender/nodes/geometry/nodes/node_geo_join_geometry.cc
index 75736ae714a..b9c9e5bd02a 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_join_geometry.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_join_geometry.cc
@@ -228,6 +228,14 @@ static void join_components(Span<const InstancesComponent *> src_components, Geo
   }
 }
 
+static void join_components(Span<const VolumeComponent *> src_components, GeometrySet &result)
+{
+  /* Not yet supported. Joining volume grids with the same name requires resampling of at least one
+   * of the grids. The cell size of the resulting volume has to be determined somehow. */
+  VolumeComponent &dst_component = result.get_component_for_write<VolumeComponent>();
+  UNUSED_VARS(src_components, dst_component);
+}
+
 template<typename Component>
 static void join_component_type(Span<const GeometrySet *> src_geometry_sets, GeometrySet &result)
 {
@@ -260,6 +268,7 @@ static void geo_node_join_geometry_exec(GeoNodeExecParams params)
   join_component_type<MeshComponent>(src_geometry_sets, geometry_set_result);
   join_component_type<PointCloudComponent>(src_geometry_sets, geometry_set_result);
   join_component_type<InstancesComponent>(src_geometry_sets, geometry_set_result);
+  join_component_type<VolumeComponent>(src_geometry_sets, geometry_set_result);
 
   params.set_output("Geometry", std::move(geometry_set_result));
 }
diff --git a/source/blender/nodes/geometry/nodes/node_geo_object_info.cc b/source/blender/nodes/geometry/nodes/node_geo_object_info.cc
index ab5e4f8964a..fe0303a5f1c 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_object_info.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_object_info.cc
@@ -19,6 +19,7 @@
 #include "BKE_mesh.h"
 #include "BKE_mesh_wrapper.h"
 #include "BKE_modifier.h"
+#include "BKE_volume.h"
 
 #include "BLI_math_matrix.h"
 
@@ -86,6 +87,16 @@ static void geo_node_object_info_exec(GeoNodeExecParams params)
           mesh_component.copy_vertex_group_names_from_object(*object);
         }
       }
+      if (object->type == OB_VOLUME) {
+        InstancesComponent &instances = geometry_set.get_component_for_write<InstancesComponent>();
+
+        if (transform_space_relative) {
+          instances.add_instance(object, location, rotation, scale);
+        }
+        else {
+          instances.add_instance(object, {0, 0, 0});
+        }
+      }
     }
   }
 
diff --git a/source/blender/nodes/geometry/nodes/node_geo_transform.cc b/source/blender/nodes/geometry/nodes/node_geo_transform.cc
index 4fe61dff72d..251fa0866ad 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_transform.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_transform.cc
@@ -14,11 +14,19 @@
  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  */
 
+#ifdef WITH_OPENVDB
+#  include <openvdb/openvdb.h>
+#endif
+
 #include "BLI_math_matrix.h"
 
 #include "DNA_pointcloud_types.h"
+#include "DNA_volume_types.h"
 
 #include "BKE_mesh.h"
+#include "BKE_volume.h"
+
+#include "DEG_depsgraph_query.h"
 
 #include "node_geometry_util.hh"
 
@@ -116,6 +124,43 @@ static void transform_instances(InstancesComponent &instances,
   }
 }
 
+static void transform_volume(Volume *volume,
+                             const float3 translation,
+                             const float3 rotation,
+                             const float3 scale,
+                             GeoNodeExecParams &params)
+{
+#ifdef WITH_OPENVDB
+  /* Scaling an axis to zero is not supported for volumes. */
+  const float3 limited_scale = {
+      (scale.x == 0.0f) ? FLT_EPSILON : scale.x,
+      (scale.y == 0.0f) ? FLT_EPSILON : scale.y,
+      (scale.z == 0.0f) ? FLT_EPSILON : scale.z,
+  };
+
+  Main *bmain = DEG_get_bmain(params.depsgraph());
+  BKE_volume_load(volume, bmain);
+
+  float matrix[4][4];
+  loc_eul_size_to_mat4(matrix, translation, rotation, limited_scale);
+
+  openvdb::Mat4s vdb_matrix;
+  memcpy(vdb_matrix.asPointer(), matrix, sizeof(float[4][4]));
+  openvdb::Mat4d vdb_matrix_d{vdb_matrix};
+
+  const int num_grids = BKE_volume_num_grids(volume);
+  for (const int i : IndexRange(num_grids)) {
+    VolumeGrid *volume_grid = BKE_volume_grid_get(volume, i);
+
+    openvdb::GridBase::Ptr grid = BKE_volume_grid_openvdb_for_write(volume, volume_grid, false);
+    openvdb::math::Transform &grid_transform = grid->transform();
+    grid_transform.postMult(vdb_matrix_d);
+  }
+#else
+  UNUSED_VARS(volume, translation, rotation, scale, params);
+#endif
+}
+
 static void geo_node_transform_exec(GeoNodeExecParams params)
 {
   GeometrySet geometry_set = params.extract_input<GeometrySet>("Geometry");
@@ -138,6 +183,11 @@ static void geo_node_transform_exec(GeoNodeExecParams params)
     transform_instances(instances, translation, rotation, scale);
   }
 
+  if (geometry_set.has_volume()) {
+    Volume *volume = geometry_set.get_volume_for_write();
+    transform_volume(volume, translation, rotation, scale, params);
+  }
+
   params.set_output("Geometry", std::move(geometry_set));
 }
 }  // namespace blender::nodes