Render: Use dependency graph for compositor/sequencer

This change makes it so a minimal dependency graph which only includes
compositor and sequencer is built for the render pipeline purposes.

Tricky part here is that it's only compositor itself and sequencer who
to use this dependency graph and IDs from it. Render engines are still
to be provided original IDs because:

- They will create dependency graph for the given scene, and currently
  it is not possible to create dependency graph from CoW scene.

- IDs from the compositor/sequencer dependency graph are "stripped",
  as in, they wouldn't have all view layers, collections or objects
	required for proper final render.

This creates annoying mess of mixing evaluated and original scene
access in various parts of the pipeline.

Fixes T63927: Compositing nodes - drivers don't really work

Reviewers: brecht

Maniphest Tasks: T63927

Differential Revision: https://developer.blender.org/D4911

1 files changed, 8 insertions, 3 deletions

diff --git a/source/blender/depsgraph/DEG_depsgraph_build.h b/source/blender/depsgraph/DEG_depsgraph_build.h
index 2d0bc6ff15b..15abc0c0a64 100644
--- a/source/blender/depsgraph/DEG_depsgraph_build.h
+++ b/source/blender/depsgraph/DEG_depsgraph_build.h
@@ -52,14 +52,19 @@ extern "C" {
 
 /* Graph Building -------------------------------- */
 
-/* Build depsgraph for the given scene, and dump results in given
- * graph container.
- */
+/* Build depsgraph for the given scene, and dump results in given graph container. */
 void DEG_graph_build_from_view_layer(struct Depsgraph *graph,
                                      struct Main *bmain,
                                      struct Scene *scene,
                                      struct ViewLayer *view_layer);
 
+/* Special version of builder which produces dependency graph suitable for the render pipeline.
+ * It will contain sequencer and compositor (if needed) and all their dependencies. */
+void DEG_graph_build_for_render_pipeline(struct Depsgraph *graph,
+                                         struct Main *bmain,
+                                         struct Scene *scene,
+                                         struct ViewLayer *view_layer);
+
 /* Tag relations from the given graph for update. */
 void DEG_graph_tag_relations_update(struct Depsgraph *graph);