Render: faster animation and re-rendering with Persistent Data

For Cycles, when enabling the Persistent Data option, the full render data
will be preserved from frame-to-frame in animation renders and between
re-renders of the scene. This means that any modifier evaluation, BVH
building, OpenGL vertex buffer uploads, etc, can be done only once for
unchanged objects. This comes at an increased memory cost.

Previously there option was named Persistent Images and had a more limited
impact on render time and memory.

When using multiple view layers, only data from a single view layer is
preserved to keep memory usage somewhat under control. However objects
shared between view layers are preserved, and so this can speedup such
renders as well, even single frame renders.

For Eevee and Workbench this option is not available, however these engines
will now always reuse the depsgraph for animation and multiple view layers.
This can significantly speed up rendering.

These engines do not support sharing the depsgraph between re-renders, due
to technical issues regarding OpenGL contexts. Support for this could be added
if those are solved, see the code comments for details.

4 files changed, 37 insertions, 14 deletions

diff --git a/source/blender/depsgraph/DEG_depsgraph.h b/source/blender/depsgraph/DEG_depsgraph.h
index 567916fdebe..f7aeca7e75f 100644
--- a/source/blender/depsgraph/DEG_depsgraph.h
+++ b/source/blender/depsgraph/DEG_depsgraph.h
@@ -139,16 +139,20 @@ void DEG_graph_time_tag_update(struct Depsgraph *depsgraph);
 void DEG_graph_id_type_tag(struct Depsgraph *depsgraph, short id_type);
 void DEG_id_type_tag(struct Main *bmain, short id_type);
 
-void DEG_ids_clear_recalc(struct Main *bmain, Depsgraph *depsgraph);
-
-/* Check if something was changed in the database and inform
- * editors about this.
- */
-void DEG_ids_check_recalc(struct Main *bmain,
-                          struct Depsgraph *depsgraph,
-                          struct Scene *scene,
-                          struct ViewLayer *view_layer,
-                          bool time);
+/* Set a depsgraph to flush updates to editors. This would be done
+ * for viewport depsgraphs, but not render or export depsgraph for example. */
+void DEG_enable_editors_update(struct Depsgraph *depsgraph);
+
+/* Check if something was changed in the database and inform editors about this,
+ * then clear recalc flags. */
+void DEG_editors_update(struct Main *bmain,
+                        struct Depsgraph *depsgraph,
+                        struct Scene *scene,
+                        struct ViewLayer *view_layer,
+                        bool time);
+
+/* Clear recalc flags after editors or renderers have handled updates. */
+void DEG_ids_clear_recalc(Depsgraph *depsgraph);
 
 /* ************************************************ */
 /* Evaluation Engine API */
diff --git a/source/blender/depsgraph/intern/depsgraph.cc b/source/blender/depsgraph/intern/depsgraph.cc
index 3d30e7e79b9..8e1ab23fae0 100644
--- a/source/blender/depsgraph/intern/depsgraph.cc
+++ b/source/blender/depsgraph/intern/depsgraph.cc
@@ -70,7 +70,8 @@ Depsgraph::Depsgraph(Main *bmain, Scene *scene, ViewLayer *view_layer, eEvaluati
       scene_cow(nullptr),
       is_active(false),
       is_evaluating(false),
-      is_render_pipeline_depsgraph(false)
+      is_render_pipeline_depsgraph(false),
+      use_editors_update(false)
 {
   BLI_spin_init(&lock);
   memset(id_type_updated, 0, sizeof(id_type_updated));
@@ -285,7 +286,9 @@ Depsgraph *DEG_graph_new(Main *bmain, Scene *scene, ViewLayer *view_layer, eEval
 }
 
 /* Replace the "owner" pointers (currently Main/Scene/ViewLayer) of this depsgraph.
- * Used during undo steps when we do want to re-use the old depsgraph data as much as possible. */
+ * Used for:
+ * - Undo steps when we do want to re-use the old depsgraph data as much as possible.
+ * - Rendering where we want to re-use objects between different view layers. */
 void DEG_graph_replace_owners(struct Depsgraph *depsgraph,
                               Main *bmain,
                               Scene *scene,
diff --git a/source/blender/depsgraph/intern/depsgraph.h b/source/blender/depsgraph/intern/depsgraph.h
index df8c8215d2f..d54aba8e25d 100644
--- a/source/blender/depsgraph/intern/depsgraph.h
+++ b/source/blender/depsgraph/intern/depsgraph.h
@@ -161,6 +161,9 @@ struct Depsgraph {
    * does not need any bases. */
   bool is_render_pipeline_depsgraph;
 
+  /* Notify editors about changes to IDs in this depsgrpah. */
+  bool use_editors_update;
+
   /* Cached list of colliders/effectors for collections and the scene
    * created along with relations, for fast lookup during evaluation. */
   Map<const ID *, ListBase *> *physics_relations[DEG_PHYSICS_RELATIONS_NUM];
diff --git a/source/blender/depsgraph/intern/depsgraph_tag.cc b/source/blender/depsgraph/intern/depsgraph_tag.cc
index 2051ee3657a..504c3956d03 100644
--- a/source/blender/depsgraph/intern/depsgraph_tag.cc
+++ b/source/blender/depsgraph/intern/depsgraph_tag.cc
@@ -816,11 +816,22 @@ void DEG_on_visible_update(Main *bmain, const bool do_time)
   }
 }
 
+void DEG_enable_editors_update(Depsgraph *depsgraph)
+{
+  deg::Depsgraph *graph = (deg::Depsgraph *)depsgraph;
+  graph->use_editors_update = true;
+}
+
 /* Check if something was changed in the database and inform
  * editors about this. */
-void DEG_ids_check_recalc(
+void DEG_editors_update(
     Main *bmain, Depsgraph *depsgraph, Scene *scene, ViewLayer *view_layer, bool time)
 {
+  deg::Depsgraph *graph = (deg::Depsgraph *)depsgraph;
+  if (!graph->use_editors_update) {
+    return;
+  }
+
   bool updated = time || DEG_id_type_any_updated(depsgraph);
 
   DEGEditorUpdateContext update_ctx = {nullptr};
@@ -829,6 +840,8 @@ void DEG_ids_check_recalc(
   update_ctx.scene = scene;
   update_ctx.view_layer = view_layer;
   deg::deg_editors_scene_update(&update_ctx, updated);
+
+  DEG_ids_clear_recalc(depsgraph);
 }
 
 static void deg_graph_clear_id_recalc_flags(ID *id)
@@ -842,7 +855,7 @@ static void deg_graph_clear_id_recalc_flags(ID *id)
   /* XXX And what about scene's master collection here? */
 }
 
-void DEG_ids_clear_recalc(Main *UNUSED(bmain), Depsgraph *depsgraph)
+void DEG_ids_clear_recalc(Depsgraph *depsgraph)
 {
   deg::Depsgraph *deg_graph = reinterpret_cast<deg::Depsgraph *>(depsgraph);
   /* TODO(sergey): Re-implement POST_UPDATE_HANDLER_WORKAROUND using entry_tags