Fix T46646: Point Cloud Density crashes on real time rendering

The issue was caused by possible use of object->derivedFinal from the render
thread, The patch tries to eliminate (or at least minimize, huh) amount of
access to the derivedFinal of a source object. It's still possible that in
the case of particle source derived mesh will be still unsafely used, but
with the patch applied we can easily change runtime part of the code and
cache derived mesh on the preparation stage.

Some ideas for the future:

- Check whether cache() was called on the point density node when calling
  calc().

- Cache derivedMesh in the runtime part of point density node to avoid
  possible remained thread conflicts.

- NULL the runtime part of the node on .blend load

Reviewers: campbellbarton, plasmasolutions

Reviewed By: plasmasolutions

Differential Revision: https://developer.blender.org/D1614

1 files changed, 11 insertions, 3 deletions

diff --git a/intern/cycles/blender/blender_shader.cpp b/intern/cycles/blender/blender_shader.cpp
index 5bbdeb6061b..3f4f1bb206b 100644
--- a/intern/cycles/blender/blender_shader.cpp
+++ b/intern/cycles/blender/blender_shader.cpp
@@ -184,6 +184,7 @@ static ShaderNode *add_node(Scene *scene,
                             BL::RenderEngine b_engine,
                             BL::BlendData b_data,
                             BL::Scene b_scene,
+                            const bool background,
                             ShaderGraph *graph,
                             BL::ShaderNodeTree b_ntree,
                             BL::ShaderNode b_node)
@@ -763,6 +764,8 @@ static ShaderNode *add_node(Scene *scene,
 
 		/* TODO(sergey): Use more proper update flag. */
 		if(true) {
+			int settings = background ? 1 : 0;  /* 1 - render settings, 0 - vewport settings. */
+			b_point_density_node.cache_point_density(b_scene, settings);
 			scene->image_manager->tag_reload_image(
 			        point_density->filename,
 			        point_density->builtin_data,
@@ -852,6 +855,7 @@ static void add_nodes(Scene *scene,
                       BL::RenderEngine b_engine,
                       BL::BlendData b_data,
                       BL::Scene b_scene,
+                      const bool background,
                       ShaderGraph *graph,
                       BL::ShaderNodeTree b_ntree,
                       const ProxyMap &proxy_input_map,
@@ -937,6 +941,7 @@ static void add_nodes(Scene *scene,
 				          b_engine,
 				          b_data,
 				          b_scene,
+				          background,
 				          graph,
 				          b_group_ntree,
 				          group_proxy_input_map,
@@ -984,6 +989,7 @@ static void add_nodes(Scene *scene,
 				                b_engine,
 				                b_data,
 				                b_scene,
+				                background,
 				                graph,
 				                b_ntree,
 				                BL::ShaderNode(*b_node));
@@ -1046,6 +1052,7 @@ static void add_nodes(Scene *scene,
                       BL::RenderEngine b_engine,
                       BL::BlendData b_data,
                       BL::Scene b_scene,
+                      const bool background,
                       ShaderGraph *graph,
                       BL::ShaderNodeTree b_ntree)
 {
@@ -1054,6 +1061,7 @@ static void add_nodes(Scene *scene,
 	          b_engine,
 	          b_data,
 	          b_scene,
+	          background,
 	          graph,
 	          b_ntree,
 	          empty_proxy_map,
@@ -1083,7 +1091,7 @@ void BlenderSync::sync_materials(bool update_all)
 			if(b_mat->use_nodes() && b_mat->node_tree()) {
 				BL::ShaderNodeTree b_ntree(b_mat->node_tree());
 
-				add_nodes(scene, b_engine, b_data, b_scene, graph, b_ntree);
+				add_nodes(scene, b_engine, b_data, b_scene, !preview, graph, b_ntree);
 			}
 			else {
 				ShaderNode *closure, *out;
@@ -1126,7 +1134,7 @@ void BlenderSync::sync_world(bool update_all)
 		if(b_world && b_world.use_nodes() && b_world.node_tree()) {
 			BL::ShaderNodeTree b_ntree(b_world.node_tree());
 
-			add_nodes(scene, b_engine, b_data, b_scene, graph, b_ntree);
+			add_nodes(scene, b_engine, b_data, b_scene, !preview, graph, b_ntree);
 
 			/* volume */
 			PointerRNA cworld = RNA_pointer_get(&b_world.ptr, "cycles");
@@ -1217,7 +1225,7 @@ void BlenderSync::sync_lamps(bool update_all)
 
 				BL::ShaderNodeTree b_ntree(b_lamp->node_tree());
 
-				add_nodes(scene, b_engine, b_data, b_scene, graph, b_ntree);
+				add_nodes(scene, b_engine, b_data, b_scene, !preview, graph, b_ntree);
 			}
 			else {
 				ShaderNode *closure, *out;