Fixed webgl_interactive_cubes_gpu example. Fixes #3707.

examples/webgl_interactive_cubes_gpu.html

@@ -112,7 +112,7 @@
 					position.y = Math.random() * 6000 - 3000;
 					position.z = Math.random() * 8000 - 4000;
 
-					var rotation = new THREE.Vector3();
+					var rotation = new THREE.Euler();
 
 					rotation.x = Math.random() * 2 * Math.PI;
 					rotation.y = Math.random() * 2 * Math.PI;