Cycles: fix instanced mesh sync being a bit too slow.

intern/cycles/blender/blender_mesh.cpp

@@ -252,6 +252,12 @@ Mesh *BlenderSync::sync_mesh(BL::Object b_ob, bool object_updated)
 		}
 	}
 
+	/* ensure we only sync instanced meshes once */
+	if(mesh_synced.find(mesh) != mesh_synced.end())
+		return mesh;
+	
+	mesh_synced.insert(mesh);
+
 	/* create derived mesh */
 	BL::Mesh b_mesh = object_to_mesh(b_ob, b_scene, true, !preview);
 	/* todo: this will crash on non-mesh types! */

intern/cycles/blender/blender_object.cpp

@@ -139,6 +139,7 @@ void BlenderSync::sync_objects(BL::SpaceView3D b_v3d)
 	light_map.pre_sync();
 	mesh_map.pre_sync();
 	object_map.pre_sync();
+	mesh_synced.clear();
 
 	/* object loop */
 	BL::Scene::objects_iterator b_ob;
@@ -177,6 +178,7 @@ void BlenderSync::sync_objects(BL::SpaceView3D b_v3d)
 		scene->mesh_manager->tag_update(scene);
 	if(object_map.post_sync())
 		scene->object_manager->tag_update(scene);
+	mesh_synced.clear();
 }
 
 CCL_NAMESPACE_END

intern/cycles/blender/blender_sync.h

@@ -92,6 +92,7 @@ private:
 	id_map<ObjectKey, Object> object_map;
 	id_map<void*, Mesh> mesh_map;
 	id_map<ObjectKey, Light> light_map;
+	set<Mesh*> mesh_synced;
 	void *world_map;
 	bool world_recalc;