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, 5 insertions, 0 deletions

diff --git a/intern/cycles/scene/scene.cpp b/intern/cycles/scene/scene.cpp
index 359e2d8e2c3..b6b53004816 100644
--- a/intern/cycles/scene/scene.cpp
+++ b/intern/cycles/scene/scene.cpp
@@ -251,6 +251,11 @@ void Scene::device_update(Device *device_, Progress &progress)
    * - Lookup tables are done a second time to handle film tables
    */
 
+  if (film->update_lightgroups(this)) {
+    light_manager->tag_update(this, ccl::LightManager::LIGHT_MODIFIED);
+    object_manager->tag_update(this, ccl::ObjectManager::OBJECT_MODIFIED);
+  }
+
   progress.set_status("Updating Shaders");
   shader_manager->device_update(device, &dscene, this, progress);