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, 16 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_layer.h b/source/blender/blenkernel/BKE_layer.h
index c877035830c..4a3917dafee 100644
--- a/source/blender/blenkernel/BKE_layer.h
+++ b/source/blender/blenkernel/BKE_layer.h
@@ -8,6 +8,7 @@
 
 #include "BKE_collection.h"
 
+#include "DNA_layer_types.h"
 #include "DNA_listBase.h"
 
 #ifdef __cplusplus
@@ -581,6 +582,21 @@ bool BKE_view_layer_has_valid_aov(struct ViewLayer *view_layer);
 struct ViewLayer *BKE_view_layer_find_with_aov(struct Scene *scene,
                                                struct ViewLayerAOV *view_layer_aov);
 
+struct ViewLayerLightgroup *BKE_view_layer_add_lightgroup(struct ViewLayer *view_layer);
+void BKE_view_layer_remove_lightgroup(struct ViewLayer *view_layer,
+                                      struct ViewLayerLightgroup *lightgroup);
+void BKE_view_layer_set_active_lightgroup(struct ViewLayer *view_layer,
+                                          struct ViewLayerLightgroup *lightgroup);
+struct ViewLayer *BKE_view_layer_find_with_lightgroup(
+    struct Scene *scene, struct ViewLayerLightgroup *view_layer_lightgroup);
+void BKE_view_layer_rename_lightgroup(ViewLayer *view_layer,
+                                      ViewLayerLightgroup *lightgroup,
+                                      const char *name);
+
+void BKE_lightgroup_membership_get(struct LightgroupMembership *lgm, char *value);
+int BKE_lightgroup_membership_length(struct LightgroupMembership *lgm);
+void BKE_lightgroup_membership_set(struct LightgroupMembership **lgm, const char *value);
+
 #ifdef __cplusplus
 }
 #endif