Cycles : add a Volume Geometry Node

This splits the volume related data (properties for rendering and attributes) of the Mesh node
into a new `Volume` node type.

This `Volume` node derives from the `Mesh` class since we generate a mesh for the bounds of the
volume, as such we can safely work on `Volumes` as if they were `Meshes`, e.g. for BVH creation.
However such code should still check for the geometry type of the object to be `MESH` or `VOLUME`
which may be bug prone if this is forgotten.

This is part of T79131.

Reviewed By: brecht

Maniphest Tasks: T79131

Differential Revision: https://developer.blender.org/D8538

1 files changed, 22 insertions, 7 deletions

diff --git a/intern/cycles/blender/blender_geometry.cpp b/intern/cycles/blender/blender_geometry.cpp
index f7e4623024d..9a82c5e9371 100644
--- a/intern/cycles/blender/blender_geometry.cpp
+++ b/intern/cycles/blender/blender_geometry.cpp
@@ -19,6 +19,7 @@
 #include "render/hair.h"
 #include "render/mesh.h"
 #include "render/object.h"
+#include "render/volume.h"
 
 #include "blender/blender_sync.h"
 #include "blender/blender_util.h"
@@ -27,6 +28,19 @@
 
 CCL_NAMESPACE_BEGIN
 
+static Geometry::Type determine_geom_type(BL::Object &b_ob, bool use_particle_hair)
+{
+  if (b_ob.type() == BL::Object::type_HAIR || use_particle_hair) {
+    return Geometry::HAIR;
+  }
+
+  if (b_ob.type() == BL::Object::type_VOLUME || object_fluid_gas_domain_find(b_ob)) {
+    return Geometry::VOLUME;
+  }
+
+  return Geometry::MESH;
+}
+
 Geometry *BlenderSync::sync_geometry(BL::Depsgraph &b_depsgraph,
                                      BL::Object &b_ob,
                                      BL::Object &b_ob_instance,
@@ -40,9 +54,7 @@ Geometry *BlenderSync::sync_geometry(BL::Depsgraph &b_depsgraph,
   BL::Material material_override = view_layer.material_override;
   Shader *default_shader = (b_ob.type() == BL::Object::type_VOLUME) ? scene->default_volume :
                                                                       scene->default_surface;
-  Geometry::Type geom_type = (b_ob.type() == BL::Object::type_HAIR || use_particle_hair) ?
-                                 Geometry::HAIR :
-                                 Geometry::MESH;
+  Geometry::Type geom_type = determine_geom_type(b_ob, use_particle_hair);
 
   /* Find shader indices. */
   vector<Shader *> used_shaders;
@@ -73,6 +85,9 @@ Geometry *BlenderSync::sync_geometry(BL::Depsgraph &b_depsgraph,
     if (geom_type == Geometry::HAIR) {
       geom = new Hair();
     }
+    else if (geom_type == Geometry::VOLUME) {
+      geom = new Volume();
+    }
     else {
       geom = new Mesh();
     }
@@ -121,13 +136,13 @@ Geometry *BlenderSync::sync_geometry(BL::Depsgraph &b_depsgraph,
 
   geom->name = ustring(b_ob_data.name().c_str());
 
-  if (b_ob.type() == BL::Object::type_HAIR || use_particle_hair) {
+  if (geom_type == Geometry::HAIR) {
     Hair *hair = static_cast<Hair *>(geom);
     sync_hair(b_depsgraph, b_ob, hair, used_shaders);
   }
-  else if (b_ob.type() == BL::Object::type_VOLUME || object_fluid_gas_domain_find(b_ob)) {
-    Mesh *mesh = static_cast<Mesh *>(geom);
-    sync_volume(b_ob, mesh, used_shaders);
+  else if (geom_type == Geometry::VOLUME) {
+    Volume *volume = static_cast<Volume *>(geom);
+    sync_volume(b_ob, volume, used_shaders);
   }
   else {
     Mesh *mesh = static_cast<Mesh *>(geom);