Geometry Nodes: refactor instances component

The main goal of this refactor is to not store Object/Collection
pointers for every individual instance. Instead instances now
store a handle for the referenced data. The actual Object/Collection
pointers are stored in a new `InstanceReference` class.

This refactor also allows for some better optimizations further down
the line, because one does not have to search through all instances
anymore to find what data is instanced.

Furthermore, this refactor makes it easier to support instancing
`GeometrySet` or any other data that has to be owned by the
`InstancesComponent`.

Differential Revision: https://developer.blender.org/D11125

1 files changed, 3 insertions, 2 deletions

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 bd42b4c11d6..de099b8062f 100644
--- a/source/blender/nodes/geometry/nodes/node_geo_object_info.cc
+++ b/source/blender/nodes/geometry/nodes/node_geo_object_info.cc
@@ -73,14 +73,15 @@ static void geo_node_object_info_exec(GeoNodeExecParams params)
 
     if (object != self_object) {
       InstancesComponent &instances = geometry_set.get_component_for_write<InstancesComponent>();
+      const int handle = instances.add_reference(*object);
 
       if (transform_space_relative) {
-        instances.add_instance(object, transform);
+        instances.add_instance(handle, transform);
       }
       else {
         float unit_transform[4][4];
         unit_m4(unit_transform);
-        instances.add_instance(object, unit_transform);
+        instances.add_instance(handle, unit_transform);
       }
     }
   }