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

2 files changed, 52 insertions, 13 deletions

diff --git a/source/blender/render/intern/include/render_types.h b/source/blender/render/intern/include/render_types.h
index e4a2afa4349..efa328cf14d 100644
--- a/source/blender/render/intern/include/render_types.h
+++ b/source/blender/render/intern/include/render_types.h
@@ -118,6 +118,11 @@ struct Render {
   /* render engine */
   struct RenderEngine *engine;
 
+  /* NOTE: This is a minimal dependency graph and evaluated scene which is enough to access view
+   * layer visibility and use for post-precessing (compositor and sequencer). */
+  Depsgraph *pipeline_depsgraph;
+  Scene *pipeline_scene_eval;
+
 #ifdef WITH_FREESTYLE
   struct Main *freestyle_bmain;
   ListBase freestyle_renders;
diff --git a/source/blender/render/intern/source/pipeline.c b/source/blender/render/intern/source/pipeline.c
index 9c1c713ab94..76767d0d1d8 100644
--- a/source/blender/render/intern/source/pipeline.c
+++ b/source/blender/render/intern/source/pipeline.c
@@ -74,6 +74,7 @@
 
 #include "DEG_depsgraph.h"
 #include "DEG_depsgraph_build.h"
+#include "DEG_depsgraph_debug.h"
 #include "DEG_depsgraph_query.h"
 
 #include "PIL_time.h"
@@ -1430,10 +1431,10 @@ static void free_all_freestyle_renders(void)
 /* returns fully composited render-result on given time step (in RenderData) */
 static void do_render_composite(Render *re)
 {
-  bNodeTree *ntree = re->scene->nodetree;
+  bNodeTree *ntree = re->pipeline_scene_eval->nodetree;
   int update_newframe = 0;
 
-  if (composite_needs_render(re->scene, 1)) {
+  if (composite_needs_render(re->pipeline_scene_eval, 1)) {
     /* save memory... free all cached images */
     ntreeFreeCache(ntree);
 
@@ -1471,7 +1472,7 @@ static void do_render_composite(Render *re)
   if (!re->test_break(re->tbh)) {
 
     if (ntree) {
-      ntreeCompositTagRender(re->scene);
+      ntreeCompositTagRender(re->pipeline_scene_eval);
     }
 
     if (ntree && re->scene->use_nodes && re->r.scemode & R_DOCOMP) {
@@ -1494,7 +1495,7 @@ static void do_render_composite(Render *re)
 
         RenderView *rv;
         for (rv = re->result->views.first; rv; rv = rv->next) {
-          ntreeCompositExecTree(re->scene,
+          ntreeCompositExecTree(re->pipeline_scene_eval,
                                 ntree,
                                 &re->r,
                                 true,
@@ -1595,12 +1596,8 @@ static void do_render_seq(Render *re)
   tot_views = BKE_scene_multiview_num_views_get(&re->r);
   ibuf_arr = MEM_mallocN(sizeof(ImBuf *) * tot_views, "Sequencer Views ImBufs");
 
-  /* TODO(sergey): Currently depsgraph is only used to check whether it is an active
-   * edit window or not to deal with unkeyed changes. We don't have depsgraph here yet,
-   * but we also dont' deal with unkeyed changes. But still nice to get proper depsgraph
-   * within tjhe render pipeline, somehow.
-   */
-  BKE_sequencer_new_render_data(re->main, NULL, re->scene, re_x, re_y, 100, true, &context);
+  BKE_sequencer_new_render_data(
+      re->main, re->pipeline_depsgraph, re->scene, re_x, re_y, 100, true, &context);
 
   /* the renderresult gets destroyed during the rendering, so we first collect all ibufs
    * and then we populate the final renderesult */
@@ -1613,7 +1610,7 @@ static void do_render_seq(Render *re)
       ibuf_arr[view_id] = IMB_dupImBuf(out);
       IMB_metadata_copy(ibuf_arr[view_id], out);
       IMB_freeImBuf(out);
-      BKE_sequencer_imbuf_from_sequencer_space(re->scene, ibuf_arr[view_id]);
+      BKE_sequencer_imbuf_from_sequencer_space(re->pipeline_scene_eval, ibuf_arr[view_id]);
     }
     else {
       ibuf_arr[view_id] = NULL;
@@ -1641,9 +1638,9 @@ static void do_render_seq(Render *re)
       }
 
       if (recurs_depth == 0) { /* with nested scenes, only free on toplevel... */
-        Editing *ed = re->scene->ed;
+        Editing *ed = re->pipeline_scene_eval->ed;
         if (ed) {
-          BKE_sequencer_free_imbuf(re->scene, &ed->seqbase, true);
+          BKE_sequencer_free_imbuf(re->pipeline_scene_eval, &ed->seqbase, true);
         }
       }
       IMB_freeImBuf(ibuf_arr[view_id]);
@@ -2071,6 +2068,32 @@ void RE_SetReports(Render *re, ReportList *reports)
   re->reports = reports;
 }
 
+static void render_update_depsgraph(Render *re)
+{
+  Scene *scene = re->scene;
+  /* TODO(sergey): This doesn't run any callbacks and doesn't do sound update. But we can not use
+   * BKE_scene_graph_update_for_newframe() because that one builds dependency graph for view layer
+   * and not for the render pipeline. */
+  DEG_evaluate_on_framechange(re->main, re->pipeline_depsgraph, CFRA);
+}
+
+static void render_init_depsgraph(Render *re)
+{
+  Scene *scene = re->scene;
+  ViewLayer *view_layer = BKE_view_layer_default_render(re->scene);
+
+  re->pipeline_depsgraph = DEG_graph_new(scene, view_layer, DAG_EVAL_RENDER);
+  DEG_debug_name_set(re->pipeline_depsgraph, "RENDER PIPELINE");
+
+  /* Make sure there is a correct evaluated scene pointer. */
+  DEG_graph_build_for_render_pipeline(re->pipeline_depsgraph, re->main, scene, view_layer);
+
+  /* Update immediately so we have proper evaluated scene. */
+  render_update_depsgraph(re);
+
+  re->pipeline_scene_eval = DEG_get_evaluated_scene(re->pipeline_depsgraph);
+}
+
 /* general Blender frame render call */
 void RE_RenderFrame(Render *re,
                     Main *bmain,
@@ -2093,6 +2116,8 @@ void RE_RenderFrame(Render *re,
     const RenderData rd = scene->r;
     MEM_reset_peak_memory();
 
+    render_init_depsgraph(re);
+
     BLI_callback_exec(re->main, (ID *)scene, BLI_CB_EVT_RENDER_PRE);
 
     do_render_all_options(re);
@@ -2490,6 +2515,8 @@ void RE_RenderAnim(Render *re,
     return;
   }
 
+  render_init_depsgraph(re);
+
   if (is_movie) {
     size_t width, height;
     int i;
@@ -2556,6 +2583,8 @@ void RE_RenderAnim(Render *re,
         BKE_animsys_evaluate_animdata(NULL, scene, &scene->id, adt, ctime, ADT_RECALC_ALL);
       }
 
+      render_update_depsgraph(re);
+
       /* only border now, todo: camera lens. (ton) */
       render_initialize_from_main(re, &rd, bmain, scene, single_layer, camera_override, 1, 0);
 
@@ -2746,6 +2775,11 @@ void RE_CleanAfterRender(Render *re)
 {
   /* Destroy the opengl context in the correct thread. */
   RE_gl_context_destroy(re);
+  if (re->pipeline_depsgraph != NULL) {
+    DEG_graph_free(re->pipeline_depsgraph);
+  }
+  re->pipeline_depsgraph = NULL;
+  re->pipeline_scene_eval = NULL;
 }
 
 /* note; repeated win/disprect calc... solve that nicer, also in compo */