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, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_internal.h b/source/blender/makesrna/intern/rna_internal.h
index 84f083cb37a..0df0be07fee 100644
--- a/source/blender/makesrna/intern/rna_internal.h
+++ b/source/blender/makesrna/intern/rna_internal.h
@@ -355,6 +355,10 @@ void rna_ViewLayer_active_aov_index_range(
     PointerRNA *ptr, int *min, int *max, int *softmin, int *softmax);
 int rna_ViewLayer_active_aov_index_get(PointerRNA *ptr);
 void rna_ViewLayer_active_aov_index_set(PointerRNA *ptr, int value);
+void rna_ViewLayer_active_lightgroup_index_range(
+    PointerRNA *ptr, int *min, int *max, int *softmin, int *softmax);
+int rna_ViewLayer_active_lightgroup_index_get(PointerRNA *ptr);
+void rna_ViewLayer_active_lightgroup_index_set(PointerRNA *ptr, int value);
 /**
  *  Set `r_rna_path` with the base view-layer path.
  *  `rna_path_buffer_size` should be at least `sizeof(ViewLayer.name) * 3`.