Fix transforms involved into navmesh baking

Within the context of parsing navigation geometry, this commit:
- added missing transform of `MultiMeshInstance`
- changed all transforms to global ones so that they don't need to be
  calculated by hand

modules/navigation/navigation_mesh_generator.cpp

@@ -140,12 +140,12 @@ void NavigationMeshGenerator::_add_faces(const PackedVector3Array &p_faces, cons
 	}
 }
 
-void NavigationMeshGenerator::_parse_geometry(Transform3D p_accumulated_transform, Node *p_node, Vector<float> &p_vertices, Vector<int> &p_indices, NavigationMesh::ParsedGeometryType p_generate_from, uint32_t p_collision_mask, bool p_recurse_children) {
+void NavigationMeshGenerator::_parse_geometry(const Transform3D &p_navmesh_transform, Node *p_node, Vector<float> &p_vertices, Vector<int> &p_indices, NavigationMesh::ParsedGeometryType p_generate_from, uint32_t p_collision_mask, bool p_recurse_children) {
 	if (Object::cast_to<MeshInstance3D>(p_node) && p_generate_from != NavigationMesh::PARSED_GEOMETRY_STATIC_COLLIDERS) {
 		MeshInstance3D *mesh_instance = Object::cast_to<MeshInstance3D>(p_node);
 		Ref<Mesh> mesh = mesh_instance->get_mesh();
 		if (mesh.is_valid()) {
-			_add_mesh(mesh, p_accumulated_transform * mesh_instance->get_transform(), p_vertices, p_indices);
+			_add_mesh(mesh, p_navmesh_transform * mesh_instance->get_global_transform(), p_vertices, p_indices);
 		}
 	}
 
@@ -159,7 +159,7 @@ void NavigationMeshGenerator::_parse_geometry(Transform3D p_accumulated_transfor
 				n = multimesh->get_instance_count();
 			}
 			for (int i = 0; i < n; i++) {
-				_add_mesh(mesh, p_accumulated_transform * multimesh->get_instance_transform(i), p_vertices, p_indices);
+				_add_mesh(mesh, p_navmesh_transform * multimesh_instance->get_global_transform() * multimesh->get_instance_transform(i), p_vertices, p_indices);
 			}
 		}
 	}
@@ -171,7 +171,7 @@ void NavigationMeshGenerator::_parse_geometry(Transform3D p_accumulated_transfor
 		if (!meshes.is_empty()) {
 			Ref<Mesh> mesh = meshes[1];
 			if (mesh.is_valid()) {
-				_add_mesh(mesh, p_accumulated_transform * csg_shape->get_transform(), p_vertices, p_indices);
+				_add_mesh(mesh, p_navmesh_transform * csg_shape->get_global_transform(), p_vertices, p_indices);
 			}
 		}
 	}
@@ -186,7 +186,7 @@ void NavigationMeshGenerator::_parse_geometry(Transform3D p_accumulated_transfor
 				if (Object::cast_to<CollisionShape3D>(child)) {
 					CollisionShape3D *col_shape = Object::cast_to<CollisionShape3D>(child);
 
-					Transform3D transform = p_accumulated_transform * static_body->get_transform() * col_shape->get_transform();
+					Transform3D transform = p_navmesh_transform * static_body->get_global_transform() * col_shape->get_transform();
 
 					Ref<Mesh> mesh;
 					Ref<Shape3D> s = col_shape->get_shape();
@@ -270,11 +270,11 @@ void NavigationMeshGenerator::_parse_geometry(Transform3D p_accumulated_transfor
 	if (gridmap) {
 		if (p_generate_from != NavigationMesh::PARSED_GEOMETRY_STATIC_COLLIDERS) {
 			Array meshes = gridmap->get_meshes();
-			Transform3D xform = gridmap->get_transform();
+			Transform3D xform = gridmap->get_global_transform();
 			for (int i = 0; i < meshes.size(); i += 2) {
 				Ref<Mesh> mesh = meshes[i + 1];
 				if (mesh.is_valid()) {
-					_add_mesh(mesh, p_accumulated_transform * xform * (Transform3D)meshes[i], p_vertices, p_indices);
+					_add_mesh(mesh, p_navmesh_transform * xform * (Transform3D)meshes[i], p_vertices, p_indices);
 				}
 			}
 		}
@@ -364,14 +364,9 @@ void NavigationMeshGenerator::_parse_geometry(Transform3D p_accumulated_transfor
 	}
 #endif
 
-	if (Object::cast_to<Node3D>(p_node)) {
-		Node3D *spatial = Object::cast_to<Node3D>(p_node);
-		p_accumulated_transform = p_accumulated_transform * spatial->get_transform();
-	}
-
 	if (p_recurse_children) {
 		for (int i = 0; i < p_node->get_child_count(); i++) {
-			_parse_geometry(p_accumulated_transform, p_node->get_child(i), p_vertices, p_indices, p_generate_from, p_collision_mask, p_recurse_children);
+			_parse_geometry(p_navmesh_transform, p_node->get_child(i), p_vertices, p_indices, p_generate_from, p_collision_mask, p_recurse_children);
 		}
 	}
 }
@@ -616,7 +611,7 @@ void NavigationMeshGenerator::bake(Ref<NavigationMesh> p_nav_mesh, Node *p_node)
 		p_node->get_tree()->get_nodes_in_group(p_nav_mesh->get_source_group_name(), &parse_nodes);
 	}
 
-	Transform3D navmesh_xform = Object::cast_to<Node3D>(p_node)->get_transform().affine_inverse();
+	Transform3D navmesh_xform = Object::cast_to<Node3D>(p_node)->get_global_transform().affine_inverse();
 	for (Node *E : parse_nodes) {
 		NavigationMesh::ParsedGeometryType geometry_type = p_nav_mesh->get_parsed_geometry_type();
 		uint32_t collision_mask = p_nav_mesh->get_collision_mask();

modules/navigation/navigation_mesh_generator.h

@@ -52,7 +52,7 @@ protected:
 	static void _add_vertex(const Vector3 &p_vec3, Vector<float> &p_vertices);
 	static void _add_mesh(const Ref<Mesh> &p_mesh, const Transform3D &p_xform, Vector<float> &p_vertices, Vector<int> &p_indices);
 	static void _add_faces(const PackedVector3Array &p_faces, const Transform3D &p_xform, Vector<float> &p_vertices, Vector<int> &p_indices);
-	static void _parse_geometry(Transform3D p_accumulated_transform, Node *p_node, Vector<float> &p_vertices, Vector<int> &p_indices, NavigationMesh::ParsedGeometryType p_generate_from, uint32_t p_collision_mask, bool p_recurse_children);
+	static void _parse_geometry(const Transform3D &p_navmesh_transform, Node *p_node, Vector<float> &p_vertices, Vector<int> &p_indices, NavigationMesh::ParsedGeometryType p_generate_from, uint32_t p_collision_mask, bool p_recurse_children);
 
 	static void _convert_detail_mesh_to_native_navigation_mesh(const rcPolyMeshDetail *p_detail_mesh, Ref<NavigationMesh> p_nav_mesh);
 	static void _build_recast_navigation_mesh(