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, 3 insertions, 0 deletions

diff --git a/intern/cycles/scene/scene.h b/intern/cycles/scene/scene.h
index e1b36899302..9e3e8d61b80 100644
--- a/intern/cycles/scene/scene.h
+++ b/intern/cycles/scene/scene.h
@@ -197,6 +197,9 @@ class Scene : public NodeOwner {
   /* Optional name. Is used for logging and reporting. */
   string name;
 
+  /* Maps from Light group names to their pass ID. */
+  map<ustring, int> lightgroups;
+
   /* data */
   BVH *bvh;
   Camera *camera;