Depsgraph: Fix cycle with rigid body and Weight Proximity

The issue is a feedback loop with point cache reset operation.

Solved by introducing extra node which ensures object's transformation
is ready for simulator input. Allows to route relations without causing
a fake dependency cycle now.

4 files changed, 23 insertions, 5 deletions

diff --git a/source/blender/depsgraph/intern/builder/deg_builder_nodes.cc b/source/blender/depsgraph/intern/builder/deg_builder_nodes.cc
index 09a79db2dbd..39806d22071 100644
--- a/source/blender/depsgraph/intern/builder/deg_builder_nodes.cc
+++ b/source/blender/depsgraph/intern/builder/deg_builder_nodes.cc
@@ -1072,8 +1072,11 @@ void DepsgraphNodeBuilder::build_rigidbody(Scene *scene)
 			if (object->type != OB_MESH) {
 				continue;
 			}
-			/* 2) create operation for flushing results */
-			/* object's transform component - where the rigidbody operation
+			add_operation_node(&object->id,
+			                   NodeType::TRANSFORM,
+			                   OperationCode::TRANSFORM_SIMULATION_INIT);
+			/* Create operation for flushing results. */
+			/* Object's transform component - where the rigidbody operation
 			 * lives. */
 			add_operation_node(&object->id,
 			                   NodeType::TRANSFORM,
diff --git a/source/blender/depsgraph/intern/builder/deg_builder_relations.cc b/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
index b10736c98f5..d4bd63f200b 100644
--- a/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
+++ b/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
@@ -934,9 +934,10 @@ void DepsgraphRelationBuilder::build_object_pointcache(Object *object)
 		int flag = -1;
 		if (ptcache_id->type == PTCACHE_TYPE_RIGIDBODY) {
 			flag = FLAG_TRANSFORM;
-			OperationKey transform_key(&object->id,
-			                           NodeType::TRANSFORM,
-			                           OperationCode::TRANSFORM_LOCAL);
+			OperationKey transform_key(
+			        &object->id,
+			        NodeType::TRANSFORM,
+			        OperationCode::TRANSFORM_SIMULATION_INIT);
 			add_relation(point_cache_key,
 			             transform_key,
 			             "Point Cache -> Rigid Body");
@@ -1731,11 +1732,19 @@ void DepsgraphRelationBuilder::build_rigidbody(Scene *scene)
 			             "Rigidbody Sim Eval -> RBO Sync");
 			/* Simulation uses object transformation after parenting and solving
 			 * contraints. */
+			OperationKey object_transform_simulation_init_key(
+			        &object->id,
+			        NodeType::TRANSFORM,
+			        OperationCode::TRANSFORM_SIMULATION_INIT);
 			OperationKey object_transform_eval_key(
 			        &object->id,
 			        NodeType::TRANSFORM,
 			        OperationCode::TRANSFORM_EVAL);
+
 			add_relation(object_transform_eval_key,
+			             object_transform_simulation_init_key,
+			             "Object Transform -> Simulation Init");
+			add_relation(object_transform_simulation_init_key,
 			             rb_simulate_key,
 			             "Object Transform -> Rigidbody Sim Eval");
 			/* Geometry must be known to create the rigid body. RBO_MESH_BASE
diff --git a/source/blender/depsgraph/intern/node/deg_node_operation.cc b/source/blender/depsgraph/intern/node/deg_node_operation.cc
index 893c108dc5a..b0b47f89acf 100644
--- a/source/blender/depsgraph/intern/node/deg_node_operation.cc
+++ b/source/blender/depsgraph/intern/node/deg_node_operation.cc
@@ -61,6 +61,8 @@ const char *operationCodeAsString(OperationCode opcode)
 			return "TRANSFORM_CONSTRAINTS";
 		case OperationCode::TRANSFORM_FINAL: return "TRANSFORM_FINAL";
 		case OperationCode::TRANSFORM_EVAL: return "TRANSFORM_EVAL";
+		case OperationCode::TRANSFORM_SIMULATION_INIT:
+			return "TRANSFORM_SIMULATION_INIT";
 		/* Rigid body. */
 		case OperationCode::RIGIDBODY_REBUILD: return "RIGIDBODY_REBUILD";
 		case OperationCode::RIGIDBODY_SIM: return "RIGIDBODY_SIM";
diff --git a/source/blender/depsgraph/intern/node/deg_node_operation.h b/source/blender/depsgraph/intern/node/deg_node_operation.h
index c6db7b012d7..56207b08d4a 100644
--- a/source/blender/depsgraph/intern/node/deg_node_operation.h
+++ b/source/blender/depsgraph/intern/node/deg_node_operation.h
@@ -76,6 +76,10 @@ enum class OperationCode {
 	TRANSFORM_CONSTRAINTS,
 	/* Handle object-level updates, mainly proxies hacks and recalc flags.  */
 	TRANSFORM_EVAL,
+	/* Initializes transformation for simulation.
+	 * For example, ensures point cache is properly reset before doing rigid
+	 * body simulation. */
+	TRANSFORM_SIMULATION_INIT,
 	/* Transform exit point */
 	TRANSFORM_FINAL,