WebGLRenderer: Reverted materialId sorting as it breaks transparent sorting. Requires deeper refactoring.

src/renderers/WebGLRenderer.js

@@ -3180,11 +3180,7 @@ THREE.WebGLRenderer = function ( parameters ) {
 
 	function painterSortStable ( a, b ) {
 
-		if ( a.materialId !== b.materialId ) {
-
-			return b.materialId - a.materialId;
-
-		} else if ( a.z !== b.z ) {
+		if ( a.z !== b.z ) {
 
 			return b.z - a.z;
 
@@ -3273,7 +3269,6 @@ THREE.WebGLRenderer = function ( parameters ) {
 			object = webglObject.object;
 
 			webglObject.id = i;
-			webglObject.materialId = object.material.id;
 			webglObject.render = false;
 
 			if ( object.visible ) {
@@ -3821,7 +3816,6 @@ THREE.WebGLRenderer = function ( parameters ) {
 				id: null,
 				buffer: buffer,
 				object: object,
-				materialId: null,
 				opaque: null,
 				transparent: null,
 				z: 0