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, 104 insertions, 0 deletions

diff --git a/source/blender/makesrna/intern/rna_scene.c b/source/blender/makesrna/intern/rna_scene.c
index 8d5d93e10ac..0960d246257 100644
--- a/source/blender/makesrna/intern/rna_scene.c
+++ b/source/blender/makesrna/intern/rna_scene.c
@@ -1767,6 +1767,10 @@ void rna_ViewLayer_pass_update(Main *bmain, Scene *activescene, PointerRNA *ptr)
     ViewLayerAOV *aov = (ViewLayerAOV *)ptr->data;
     view_layer = BKE_view_layer_find_with_aov(scene, aov);
   }
+  else if (ptr->type == &RNA_Lightgroup) {
+    ViewLayerLightgroup *lightgroup = (ViewLayerLightgroup *)ptr->data;
+    view_layer = BKE_view_layer_find_with_lightgroup(scene, lightgroup);
+  }
 
   if (view_layer) {
     RenderEngineType *engine_type = RE_engines_find(scene->r.engine);
@@ -2447,6 +2451,49 @@ void rna_ViewLayer_active_aov_index_set(PointerRNA *ptr, int value)
   view_layer->active_aov = aov;
 }
 
+void rna_ViewLayer_active_lightgroup_index_range(
+    PointerRNA *ptr, int *min, int *max, int *UNUSED(softmin), int *UNUSED(softmax))
+{
+  ViewLayer *view_layer = (ViewLayer *)ptr->data;
+
+  *min = 0;
+  *max = max_ii(0, BLI_listbase_count(&view_layer->lightgroups) - 1);
+}
+
+int rna_ViewLayer_active_lightgroup_index_get(PointerRNA *ptr)
+{
+  ViewLayer *view_layer = (ViewLayer *)ptr->data;
+  return BLI_findindex(&view_layer->lightgroups, view_layer->active_lightgroup);
+}
+
+void rna_ViewLayer_active_lightgroup_index_set(PointerRNA *ptr, int value)
+{
+  ViewLayer *view_layer = (ViewLayer *)ptr->data;
+  ViewLayerLightgroup *lightgroup = BLI_findlink(&view_layer->lightgroups, value);
+  view_layer->active_lightgroup = lightgroup;
+}
+
+static void rna_ViewLayerLightgroup_name_get(PointerRNA *ptr, char *value)
+{
+  ViewLayerLightgroup *lightgroup = (ViewLayerLightgroup *)ptr->data;
+  BLI_strncpy(value, lightgroup->name, sizeof(lightgroup->name));
+}
+
+static int rna_ViewLayerLightgroup_name_length(PointerRNA *ptr)
+{
+  ViewLayerLightgroup *lightgroup = (ViewLayerLightgroup *)ptr->data;
+  return strlen(lightgroup->name);
+}
+
+static void rna_ViewLayerLightgroup_name_set(PointerRNA *ptr, const char *value)
+{
+  ViewLayerLightgroup *lightgroup = (ViewLayerLightgroup *)ptr->data;
+  Scene *scene = (Scene *)ptr->owner_id;
+  ViewLayer *view_layer = BKE_view_layer_find_with_lightgroup(scene, lightgroup);
+
+  BKE_view_layer_rename_lightgroup(view_layer, lightgroup, value);
+}
+
 /* Fake value, used internally (not saved to DNA). */
 #  define V3D_ORIENT_DEFAULT -1
 
@@ -4156,6 +4203,43 @@ static void rna_def_view_layer_aov(BlenderRNA *brna)
   RNA_def_property_update(prop, NC_SCENE | ND_RENDER_OPTIONS, "rna_ViewLayer_pass_update");
 }
 
+static void rna_def_view_layer_lightgroups(BlenderRNA *brna, PropertyRNA *cprop)
+{
+  StructRNA *srna;
+  /*  PropertyRNA *prop; */
+
+  FunctionRNA *func;
+  PropertyRNA *parm;
+
+  RNA_def_property_srna(cprop, "Lightgroups");
+  srna = RNA_def_struct(brna, "Lightgroups", NULL);
+  RNA_def_struct_sdna(srna, "ViewLayer");
+  RNA_def_struct_ui_text(srna, "List of Lightgroups", "Collection of Lightgroups");
+
+  func = RNA_def_function(srna, "add", "BKE_view_layer_add_lightgroup");
+  parm = RNA_def_pointer(func, "lightgroup", "Lightgroup", "", "Newly created Lightgroup");
+  RNA_def_function_return(func, parm);
+}
+
+static void rna_def_view_layer_lightgroup(BlenderRNA *brna)
+{
+  StructRNA *srna;
+  PropertyRNA *prop;
+  srna = RNA_def_struct(brna, "Lightgroup", NULL);
+  RNA_def_struct_sdna(srna, "ViewLayerLightgroup");
+  RNA_def_struct_ui_text(srna, "Light Group", "");
+
+  prop = RNA_def_property(srna, "name", PROP_STRING, PROP_NONE);
+  RNA_def_property_clear_flag(prop, PROP_ANIMATABLE);
+  RNA_def_property_string_funcs(prop,
+                                "rna_ViewLayerLightgroup_name_get",
+                                "rna_ViewLayerLightgroup_name_length",
+                                "rna_ViewLayerLightgroup_name_set");
+  RNA_def_property_ui_text(prop, "Name", "Name of the Lightgroup");
+  RNA_def_property_update(prop, NC_SCENE | ND_RENDER_OPTIONS, "rna_ViewLayer_pass_update");
+  RNA_def_struct_name_property(srna, prop);
+}
+
 void rna_def_view_layer_common(BlenderRNA *brna, StructRNA *srna, const bool scene)
 {
   PropertyRNA *prop;
@@ -4226,6 +4310,25 @@ void rna_def_view_layer_common(BlenderRNA *brna, StructRNA *srna, const bool sce
     RNA_def_property_ui_text(prop, "Active AOV Index", "Index of active aov");
     RNA_def_property_update(prop, NC_SCENE | ND_RENDER_OPTIONS, NULL);
 
+    prop = RNA_def_property(srna, "lightgroups", PROP_COLLECTION, PROP_NONE);
+    RNA_def_property_collection_sdna(prop, NULL, "lightgroups", NULL);
+    RNA_def_property_struct_type(prop, "Lightgroup");
+    RNA_def_property_ui_text(prop, "Light Groups", "");
+    rna_def_view_layer_lightgroups(brna, prop);
+
+    prop = RNA_def_property(srna, "active_lightgroup", PROP_POINTER, PROP_NONE);
+    RNA_def_property_struct_type(prop, "Lightgroup");
+    RNA_def_property_clear_flag(prop, PROP_EDITABLE);
+    RNA_def_property_ui_text(prop, "Light Groups", "Active Lightgroup");
+
+    prop = RNA_def_property(srna, "active_lightgroup_index", PROP_INT, PROP_UNSIGNED);
+    RNA_def_property_int_funcs(prop,
+                               "rna_ViewLayer_active_lightgroup_index_get",
+                               "rna_ViewLayer_active_lightgroup_index_set",
+                               "rna_ViewLayer_active_lightgroup_index_range");
+    RNA_def_property_ui_text(prop, "Active Lightgroup Index", "Index of active lightgroup");
+    RNA_def_property_update(prop, NC_SCENE | ND_RENDER_OPTIONS, NULL);
+
     prop = RNA_def_property(srna, "use_pass_cryptomatte_object", PROP_BOOLEAN, PROP_NONE);
     RNA_def_property_boolean_sdna(prop, NULL, "cryptomatte_flag", VIEW_LAYER_CRYPTOMATTE_OBJECT);
     RNA_def_property_ui_text(
@@ -8088,6 +8191,7 @@ void RNA_def_scene(BlenderRNA *brna)
   rna_def_scene_display(brna);
   rna_def_scene_eevee(brna);
   rna_def_view_layer_aov(brna);
+  rna_def_view_layer_lightgroup(brna);
   rna_def_view_layer_eevee(brna);
   rna_def_scene_gpencil(brna);
   RNA_define_animate_sdna(true);