Depsgraph: Run rigid body after modifiers are ready

This makes it so modifiers are using object transform prior
to the rigid body simulation, and then result of modifier
stack is fed to the solver.

Solves dependency cycle which was happening when object's
modifier was dependent on the modifier transform.

While now it is not possible to change simulation, things
are somewhat more clear and reliable in other ways.
For example previously, solver was using derives mesh from
a previous step in time, which causes unfixable simulation
issues (with intersections and such)

Fixex T57589: 2.79 Rigid Body Sim. Does Not Behave The Same In 2.8
Fixex T61256: Compositing scenes causes crash, but rendering separately does not
Fixes T61262: Armature and rigid body crash
Fixes T61346: Rigid body with modifiers incorrect work

1 files changed, 94 insertions, 86 deletions

diff --git a/source/blender/depsgraph/intern/builder/deg_builder_relations.cc b/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
index 0888105c248..41e6fdf5399 100644
--- a/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
+++ b/source/blender/depsgraph/intern/builder/deg_builder_relations.cc
@@ -285,13 +285,23 @@ void DepsgraphRelationBuilder::add_modifier_to_transform_relation(
 	/* Geometry operation, this is where relation will be wired to. */
 	OperationNode *geometry_operation_node =
 	        handle->node->get_entry_operation();
-	BLI_assert(geometry_operation_node->owner->type == NodeType::GEOMETRY);
+	ComponentNode *geometry_component = geometry_operation_node->owner;
+	BLI_assert(geometry_component->type == NodeType::GEOMETRY);
+	IDNode *id_node = geometry_component->owner;
 	/* Transform operation, the source of the relation. */
+	ComponentNode *transform_component =
+	        id_node->find_component(NodeType::TRANSFORM);
 	ID *id = geometry_operation_node->owner->owner->id_orig;
-	ComponentKey transform_component_key(id, NodeType::TRANSFORM);
-	Node *transform_node = get_node(transform_component_key);
-	OperationNode *transform_operation_node =
-	        transform_node->get_exit_operation();
+	BLI_assert(GS(id->name) == ID_OB);
+	Object *object = reinterpret_cast<Object *>(id);
+	OperationNode *transform_operation_node = NULL;
+	if (object->rigidbody_object == NULL) {
+		transform_operation_node = transform_component->get_exit_operation();
+	}
+	else {
+		transform_operation_node = transform_component->get_operation(
+		        OperationCode::TRANSFORM_EVAL);
+	}
 	/* Wire up the actual relation. */
 	add_operation_relation(
 	        transform_operation_node, geometry_operation_node, description);
@@ -657,14 +667,7 @@ void DepsgraphRelationBuilder::build_object(Base *base, Object *object)
 		add_relation(ob_eval_key, final_transform_key, "Eval");
 	}
 	else {
-		/* NOTE: Keep an eye here, we skip some relations here to "streamline"
-		 * dependencies and avoid transitive relations which causes overhead.
-		 * But once we get rid of uber eval node this will need reconsideration. */
-		if (object->rigidbody_object == NULL) {
-			/* Rigid body will hook up another node in between, so skip
-			 * relation here to avoid transitive relation. */
-			add_relation(base_op_key, ob_eval_key, "Eval");
-		}
+		add_relation(base_op_key, ob_eval_key, "Eval");
 		add_relation(ob_eval_key, final_transform_key, "Eval");
 	}
 	/* Animation data */
@@ -1619,84 +1622,80 @@ void DepsgraphRelationBuilder::build_world(World *world)
 void DepsgraphRelationBuilder::build_rigidbody(Scene *scene)
 {
 	RigidBodyWorld *rbw = scene->rigidbody_world;
-
-	OperationKey init_key(&scene->id, NodeType::TRANSFORM, OperationCode::RIGIDBODY_REBUILD);
-	OperationKey sim_key(&scene->id, NodeType::TRANSFORM, OperationCode::RIGIDBODY_SIM);
-
-	/* rel between the two sim-nodes */
-	add_relation(init_key, sim_key, "Rigidbody [Init -> SimStep]");
-
-	/* set up dependencies between these operations and other builtin nodes --------------- */
-
-	/* effectors */
+	OperationKey rb_init_key(&scene->id,
+	                      NodeType::TRANSFORM,
+	                      OperationCode::RIGIDBODY_REBUILD);
+	OperationKey rb_simulate_key(&scene->id,
+	                             NodeType::TRANSFORM,
+	                             OperationCode::RIGIDBODY_SIM);
+	/* Simulation depends on time. */
+	TimeSourceKey time_src_key;
+	add_relation(time_src_key, rb_init_key, "TimeSrc -> Rigidbody Init");
+	/* Simulation should always be run after initialization. */
+	/* NOTE: It is possible in theory to have dependency cycle which involves
+	 * this relation. We never want it to be killed. */
+	add_relation(rb_init_key,
+	             rb_simulate_key,
+	             "Rigidbody [Init -> SimStep]",
+	             RELATION_FLAG_GODMODE);
+	/* Effectors should be evaluated at the time simulation is being
+	 * initialized.
+	 * TODO(sergey): Verify that it indeed goes to initialization and not to a
+	 * simulation. */
 	ListBase *relations = build_effector_relations(graph_, rbw->effector_weights->group);
 	LISTBASE_FOREACH (EffectorRelation *, relation, relations) {
-		ComponentKey eff_key(&relation->ob->id, NodeType::TRANSFORM);
-		add_relation(eff_key, init_key, "RigidBody Field");
-		// FIXME add relations so pointache is marked as outdated when effectors are modified
+		ComponentKey effector_transform_key(
+		        &relation->ob->id, NodeType::TRANSFORM);
+		add_relation(effector_transform_key, rb_init_key, "RigidBody Field");
 	}
-
-	/* time dependency */
-	TimeSourceKey time_src_key;
-	add_relation(time_src_key, init_key, "TimeSrc -> Rigidbody Reset/Rebuild (Optional)");
-
-	/* objects - simulation participants */
+	/* Objects. */
 	if (rbw->group != NULL) {
 		build_collection(NULL, NULL, rbw->group);
-
 		FOREACH_COLLECTION_OBJECT_RECURSIVE_BEGIN(rbw->group, object)
 		{
 			if (object->type != OB_MESH) {
 				continue;
 			}
-
-			/* hook up evaluation order...
-			 * 1) flushing rigidbody results follows base transforms being applied
-			 * 2) rigidbody flushing can only be performed after simulation has been run
-			 *
-			 * 3) simulation needs to know base transforms to figure out what to do
-			 *    XXX: there's probably a difference between passive and active
-			 *         - passive don't change, so may need to know full transform... */
-			OperationKey rbo_key(&object->id, NodeType::TRANSFORM, OperationCode::RIGIDBODY_TRANSFORM_COPY);
-
-			OperationCode trans_opcode = object->parent ? OperationCode::TRANSFORM_PARENT
-			                                            : OperationCode::TRANSFORM_LOCAL;
-			OperationKey trans_op(&object->id, NodeType::TRANSFORM, trans_opcode);
-
-			add_relation(sim_key, rbo_key, "Rigidbody Sim Eval -> RBO Sync");
-
-			/* Geometry must be known to create the rigid body. RBO_MESH_BASE uses the non-evaluated
-			 * mesh, so then the evaluation is unnecessary. */
-			if (object->rigidbody_object != NULL && object->rigidbody_object->mesh_source != RBO_MESH_BASE) {
-				ComponentKey geom_key(&object->id, NodeType::GEOMETRY);
-				add_relation(geom_key, init_key, "Object Geom Eval -> Rigidbody Rebuild");
-			}
-
-			/* if constraints exist, those depend on the result of the rigidbody sim
-			 * - This allows constraints to modify the result of the sim (i.e. clamping)
-			 *   while still allowing the sim to depend on some changes to the objects.
-			 *   Also, since constraints are hooked up to the final nodes, this link
-			 *   means that we can also fit in there too...
-			 * - Later, it might be good to include a constraint in the stack allowing us
-			 *   to control whether rigidbody eval gets interleaved into the constraint stack */
-			if (object->constraints.first) {
-				OperationKey constraint_key(&object->id,
-				                            NodeType::TRANSFORM,
-				                            OperationCode::TRANSFORM_CONSTRAINTS);
-				add_relation(rbo_key, constraint_key, "RBO Sync -> Ob Constraints");
-			}
-			else {
-				/* Transform evaluation depends on rigidbody. */
-				OperationKey transform_eval_key(&object->id,
-				                                NodeType::TRANSFORM,
-				                                OperationCode::TRANSFORM_EVAL);
-				add_relation(rbo_key,
-				             transform_eval_key,
-				             "RBO Sync -> Transform Eval");
+			OperationKey rb_transform_copy_key(
+			        &object->id,
+			        NodeType::TRANSFORM,
+			        OperationCode::RIGIDBODY_TRANSFORM_COPY);
+			/* Rigid body synchronization depends on the actual simulation. */
+			add_relation(rb_simulate_key,
+			             rb_transform_copy_key,
+			             "Rigidbody Sim Eval -> RBO Sync");
+			/* Simulation uses object transformation after parenting and solving
+			 * contraints. */
+			OperationKey object_transform_eval_key(
+			        &object->id,
+			        NodeType::TRANSFORM,
+			        OperationCode::TRANSFORM_EVAL);
+			add_relation(object_transform_eval_key,
+			             rb_simulate_key,
+			             "Object Transform -> Rigidbody Sim Eval");
+			/* Geometry must be known to create the rigid body. RBO_MESH_BASE
+			 * uses the non-evaluated mesh, so then the evaluation is
+			 * unnecessary. */
+			if (object->rigidbody_object != NULL &&
+			    object->rigidbody_object->mesh_source != RBO_MESH_BASE)
+			{
+				/* NOTE: We prefer this relation to be never killed, to avoid
+				 * access partially evaluated mesh from solver. */
+				ComponentKey object_geometry_key(
+				        &object->id, NodeType::GEOMETRY);
+				add_relation(object_geometry_key,
+				             rb_simulate_key,
+				             "Object Geom Eval -> Rigidbody Rebuild",
+				             RELATION_FLAG_GODMODE);
 			}
-
-			/* Needed to get correct base values. */
-			add_relation(trans_op, sim_key, "Base Ob Transform -> Rigidbody Sim Eval");
+			/* Final transform is whetever solver gave to us. */
+			OperationKey object_transform_final_key(
+			        &object->id,
+			        NodeType::TRANSFORM,
+			        OperationCode::TRANSFORM_FINAL);
+			add_relation(rb_transform_copy_key,
+			             object_transform_final_key,
+			             "Rigidbody Sync -> Transform Final");
 		}
 		FOREACH_COLLECTION_OBJECT_RECURSIVE_END;
 	}
@@ -1706,7 +1705,8 @@ void DepsgraphRelationBuilder::build_rigidbody(Scene *scene)
 		{
 			RigidBodyCon *rbc = object->rigidbody_constraint;
 			if (rbc == NULL || rbc->ob1 == NULL || rbc->ob2 == NULL) {
-				/* When either ob1 or ob2 is NULL, the constraint doesn't work. */
+				/* When either ob1 or ob2 is NULL, the constraint doesn't
+				 * work. */
 				continue;
 			}
 			/* Make sure indirectly linked objects are fully built. */
@@ -1716,13 +1716,21 @@ void DepsgraphRelationBuilder::build_rigidbody(Scene *scene)
 			/* final result of the constraint object's transform controls how
 			 * the constraint affects the physics sim for these objects. */
 			ComponentKey trans_key(&object->id, NodeType::TRANSFORM);
-			OperationKey ob1_key(&rbc->ob1->id, NodeType::TRANSFORM, OperationCode::RIGIDBODY_TRANSFORM_COPY);
-			OperationKey ob2_key(&rbc->ob2->id, NodeType::TRANSFORM, OperationCode::RIGIDBODY_TRANSFORM_COPY);
+			OperationKey ob1_key(&rbc->ob1->id,
+			                     NodeType::TRANSFORM,
+			                     OperationCode::RIGIDBODY_TRANSFORM_COPY);
+			OperationKey ob2_key(&rbc->ob2->id,
+			                     NodeType::TRANSFORM,
+			                     OperationCode::RIGIDBODY_TRANSFORM_COPY);
 			/* Constrained-objects sync depends on the constraint-holder. */
-			add_relation(trans_key, ob1_key, "RigidBodyConstraint -> RBC.Object_1");
-			add_relation(trans_key, ob2_key, "RigidBodyConstraint -> RBC.Object_2");
+			add_relation(
+			        trans_key, ob1_key, "RigidBodyConstraint -> RBC.Object_1");
+			add_relation(
+			        trans_key, ob2_key, "RigidBodyConstraint -> RBC.Object_2");
 			/* Ensure that sim depends on this constraint's transform. */
-			add_relation(trans_key, sim_key, "RigidBodyConstraint Transform -> RB Simulation");
+			add_relation(trans_key,
+			             rb_simulate_key,
+			             "RigidBodyConstraint Transform -> RB Simulation");
 		}
 		FOREACH_COLLECTION_OBJECT_RECURSIVE_END;
 	}