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, 61 insertions, 25 deletions

diff --git a/source/blender/depsgraph/intern/depsgraph_build.cc b/source/blender/depsgraph/intern/depsgraph_build.cc
index dd2979160cd..138b23888b4 100644
--- a/source/blender/depsgraph/intern/depsgraph_build.cc
+++ b/source/blender/depsgraph/intern/depsgraph_build.cc
@@ -222,9 +222,33 @@ struct Depsgraph *DEG_get_graph_from_handle(struct DepsNodeHandle *node_handle)
 /* ******************** */
 /* Graph Building API's */
 
-/* Build depsgraph for the given scene layer, and dump results in given
- * graph container.
- */
+static void graph_build_finalize_common(DEG::Depsgraph *deg_graph, Main *bmain)
+{
+  /* Detect and solve cycles. */
+  DEG::deg_graph_detect_cycles(deg_graph);
+  /* Simplify the graph by removing redundant relations (to optimize
+   * traversal later). */
+  /* TODO: it would be useful to have an option to disable this in cases where
+   *       it is causing trouble. */
+  if (G.debug_value == 799) {
+    DEG::deg_graph_transitive_reduction(deg_graph);
+  }
+  /* Store pointers to commonly used valuated datablocks. */
+  deg_graph->scene_cow = (Scene *)deg_graph->get_cow_id(&deg_graph->scene->id);
+  /* Flush visibility layer and re-schedule nodes for update. */
+  DEG::deg_graph_build_finalize(bmain, deg_graph);
+  DEG_graph_on_visible_update(bmain, reinterpret_cast<::Depsgraph *>(deg_graph));
+#if 0
+  if (!DEG_debug_consistency_check(deg_graph)) {
+    printf("Consistency validation failed, ABORTING!\n");
+    abort();
+  }
+#endif
+  /* Relations are up to date. */
+  deg_graph->need_update = false;
+}
+
+/* Build depsgraph for the given scene layer, and dump results in given graph container. */
 void DEG_graph_build_from_view_layer(Depsgraph *graph,
                                      Main *bmain,
                                      Scene *scene,
@@ -245,34 +269,46 @@ void DEG_graph_build_from_view_layer(Depsgraph *graph,
   node_builder.begin_build();
   node_builder.build_view_layer(scene, view_layer, DEG::DEG_ID_LINKED_DIRECTLY);
   node_builder.end_build();
-  /* Hook up relationships between operations - to determine evaluation
-   * order. */
+  /* Hook up relationships between operations - to determine evaluation order. */
   DEG::DepsgraphRelationBuilder relation_builder(bmain, deg_graph, &builder_cache);
   relation_builder.begin_build();
   relation_builder.build_view_layer(scene, view_layer);
   relation_builder.build_copy_on_write_relations();
-  /* Detect and solve cycles. */
-  DEG::deg_graph_detect_cycles(deg_graph);
-  /* Simplify the graph by removing redundant relations (to optimize
-   * traversal later). */
-  /* TODO: it would be useful to have an option to disable this in cases where
-   *       it is causing trouble. */
-  if (G.debug_value == 799) {
-    DEG::deg_graph_transitive_reduction(deg_graph);
+  /* Finalize building. */
+  graph_build_finalize_common(deg_graph, bmain);
+  /* Finish statistics. */
+  if (G.debug & (G_DEBUG_DEPSGRAPH_BUILD | G_DEBUG_DEPSGRAPH_TIME)) {
+    printf("Depsgraph built in %f seconds.\n", PIL_check_seconds_timer() - start_time);
   }
-  /* Store pointers to commonly used valuated datablocks. */
-  deg_graph->scene_cow = (Scene *)deg_graph->get_cow_id(&deg_graph->scene->id);
-  /* Flush visibility layer and re-schedule nodes for update. */
-  DEG::deg_graph_build_finalize(bmain, deg_graph);
-  DEG_graph_on_visible_update(bmain, graph);
-#if 0
-  if (!DEG_debug_consistency_check(deg_graph)) {
-    printf("Consistency validation failed, ABORTING!\n");
-    abort();
+}
+
+void DEG_graph_build_for_render_pipeline(Depsgraph *graph,
+                                         Main *bmain,
+                                         Scene *scene,
+                                         ViewLayer * /*view_layer*/)
+{
+  double start_time = 0.0;
+  if (G.debug & (G_DEBUG_DEPSGRAPH_BUILD | G_DEBUG_DEPSGRAPH_TIME)) {
+    start_time = PIL_check_seconds_timer();
   }
-#endif
-  /* Relations are up to date. */
-  deg_graph->need_update = false;
+  DEG::Depsgraph *deg_graph = reinterpret_cast<DEG::Depsgraph *>(graph);
+  /* Perform sanity checks. */
+  BLI_assert(deg_graph->scene == scene);
+  deg_graph->is_render_pipeline_depsgraph = true;
+  DEG::DepsgraphBuilderCache builder_cache;
+  /* Generate all the nodes in the graph first */
+  DEG::DepsgraphNodeBuilder node_builder(bmain, deg_graph, &builder_cache);
+  node_builder.begin_build();
+  node_builder.build_scene_render(scene);
+  node_builder.end_build();
+  /* Hook up relationships between operations - to determine evaluation
+   * order. */
+  DEG::DepsgraphRelationBuilder relation_builder(bmain, deg_graph, &builder_cache);
+  relation_builder.begin_build();
+  relation_builder.build_scene_render(scene);
+  relation_builder.build_copy_on_write_relations();
+  /* Finalize building. */
+  graph_build_finalize_common(deg_graph, bmain);
   /* Finish statistics. */
   if (G.debug & (G_DEBUG_DEPSGRAPH_BUILD | G_DEBUG_DEPSGRAPH_TIME)) {
     printf("Depsgraph built in %f seconds.\n", PIL_check_seconds_timer() - start_time);