Cycles: Add support for light groups

Light groups are a type of pass that only contains lighting from a subset of light sources.
They are created in the View layer, and light sources (lamps, objects with emissive materials
and/or the environment) can be assigned to a group.

Currently, each light group ends up generating its own version of the Combined pass.
In the future, additional types of passes (e.g. shadowcatcher) might be getting their own
per-lightgroup versions.

The lightgroup creation and assignment is not Cycles-specific, so Eevee or external render
engines could make use of it in the future.

Note that Lightgroups are identified by their name - therefore, the name of the Lightgroup
in the View Layer and the name that's set in an object's settings must match for it to be
included.
Currently, changing a Lightgroup's name does not update objects - this is planned for the
future, along with other features such as denoising for light groups and viewing them in
preview renders.

Original patch by Alex Fuller (@mistaed), with some polishing by Lukas Stockner (@lukasstockner97).

Differential Revision: https://developer.blender.org/D12871

1 files changed, 4 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_object_types.h b/source/blender/makesdna/DNA_object_types.h
index 30f80110f6e..54627e711ff 100644
--- a/source/blender/makesdna/DNA_object_types.h
+++ b/source/blender/makesdna/DNA_object_types.h
@@ -31,6 +31,7 @@ struct Curve;
 struct FluidsimSettings;
 struct GeometrySet;
 struct Ipo;
+struct LightgroupMembership;
 struct Material;
 struct Mesh;
 struct Object;
@@ -434,8 +435,10 @@ typedef struct Object {
 
   ObjectLineArt lineart;
 
+  /** Lightgroup membership information. */
+  struct LightgroupMembership *lightgroup;
+
   /** Runtime evaluation data (keep last). */
-  void *_pad9;
   Object_Runtime runtime;
 } Object;