Fix T75686: Animating scene audio volume doesn't work

Scene audio volume changes require the scene to be tagged with
`ID_RECALC_AUDIO_VOLUME` (see `BKE_scene_update_sound()`). Tagging
happens in the RNA update function `rna_Scene_volume_update()`, but that
function is not called by the animation system. As a result, animated
volume changes are not sent to the audio system.

This commit adds a new depsgraph operation node that sets this tag when
necessary, so that the animated values are used in the rest of the
depsgraph evaluation.

Reviewed By: sergey

Differential Revision: https://developer.blender.org/D7429

source/blender/blenkernel/BKE_scene.h

@@ -141,6 +141,7 @@ int BKE_scene_orientation_slot_get_index(const struct TransformOrientationSlot *
 /* **  Scene evaluation ** */
 
 void BKE_scene_update_sound(struct Depsgraph *depsgraph, struct Main *bmain);
+void BKE_scene_update_tag_audio_volume(struct Depsgraph *, struct Scene *scene);
 
 void BKE_scene_graph_update_tagged(struct Depsgraph *depsgraph, struct Main *bmain);
 void BKE_scene_graph_evaluated_ensure(struct Depsgraph *depsgraph, struct Main *bmain);

source/blender/blenkernel/intern/scene.c

@@ -1278,6 +1278,14 @@ void BKE_scene_update_sound(Depsgraph *depsgraph, Main *bmain)
   BKE_sound_update_scene(depsgraph, scene);
 }
 
+void BKE_scene_update_tag_audio_volume(Depsgraph *UNUSED(depsgraph), Scene *scene)
+{
+  BLI_assert(DEG_is_evaluated_id(&scene->id));
+  /* The volume is actually updated in BKE_scene_update_sound(), from either
+   * scene_graph_update_tagged() or from BKE_scene_graph_update_for_newframe(). */
+  scene->id.recalc |= ID_RECALC_AUDIO_VOLUME;
+}
+
 /* TODO(sergey): This actually should become view_layer_graph or so.
  * Same applies to update_for_newframe.
  *

source/blender/depsgraph/intern/builder/deg_builder_nodes.cc

@@ -1736,7 +1736,14 @@ void DepsgraphNodeBuilder::build_scene_audio(Scene *scene)
   if (built_map_.checkIsBuiltAndTag(scene, BuilderMap::TAG_SCENE_AUDIO)) {
     return;
   }
+
   add_operation_node(&scene->id, NodeType::AUDIO, OperationCode::SOUND_EVAL);
+
+  Scene *scene_cow = get_cow_datablock(scene);
+  add_operation_node(&scene->id,
+                     NodeType::AUDIO,
+                     OperationCode::AUDIO_VOLUME,
+                     function_bind(BKE_scene_update_tag_audio_volume, _1, scene_cow));
 }
 
 void DepsgraphNodeBuilder::build_scene_speakers(Scene * /*scene*/, ViewLayer *view_layer)

source/blender/depsgraph/intern/builder/deg_builder_relations.cc

@@ -2544,8 +2544,16 @@ void DepsgraphRelationBuilder::build_scene_sequencer(Scene *scene)
   }
 }
 
-void DepsgraphRelationBuilder::build_scene_audio(Scene * /*scene*/)
+void DepsgraphRelationBuilder::build_scene_audio(Scene *scene)
 {
+  OperationKey scene_audio_volume_key(&scene->id, NodeType::AUDIO, OperationCode::AUDIO_VOLUME);
+  OperationKey scene_sound_eval_key(&scene->id, NodeType::AUDIO, OperationCode::SOUND_EVAL);
+  add_relation(scene_audio_volume_key, scene_sound_eval_key, "Audio Volume -> Sound");
+
+  if (scene->audio.flag & AUDIO_VOLUME_ANIMATED) {
+    ComponentKey scene_anim_key(&scene->id, NodeType::ANIMATION);
+    add_relation(scene_anim_key, scene_audio_volume_key, "Animation -> Audio Volume");
+  }
 }
 
 void DepsgraphRelationBuilder::build_scene_speakers(Scene * /*scene*/, ViewLayer *view_layer)

source/blender/depsgraph/intern/node/deg_node_operation.cc

@@ -61,6 +61,8 @@ const char *operationCodeAsString(OperationCode opcode)
     /* Scene related. */
     case OperationCode::SCENE_EVAL:
       return "SCENE_EVAL";
+    case OperationCode::AUDIO_VOLUME:
+      return "AUDIO_VOLUME";
     /* Object related. */
     case OperationCode::OBJECT_BASE_FLAGS:
       return "OBJECT_BASE_FLAGS";

source/blender/depsgraph/intern/node/deg_node_operation.h

@@ -60,6 +60,7 @@ enum class OperationCode {
 
   /* Scene related. ------------------------------------------------------- */
   SCENE_EVAL,
+  AUDIO_VOLUME,
 
   /* Object related. ------------------------------------------------------ */
   OBJECT_BASE_FLAGS,