              var matRight = new THREE.MeshPhongMaterial( { color: 0x00ff00, side:THREE.DoubleSide, opacity:0.3, transparent:true } );
                var planeRight = new THREE.Mesh( planeGeo, matRight );
                planeRight.name = "right";
                planeRight.position.x = 10;
                planeRight.position.y = 0;
                planeRight.rotateY( - Math.PI / 2 );
                walls.add(planeRight);

                var matLeft = new THREE.MeshPhongMaterial( { color: 0xff000