        planeBack.position.y = 0;
                walls.add(planeBack);

                var matFront = new THREE.MeshPhongMaterial( { color: 0xffffff, side:THREE.DoubleSide, opacity:0.3, transparent:true  } );
                var planeFront = new THREE.Mesh( planeGeo, matFront );
                planeFront.name = "front";
                planeFront.position.z = 10;
                planeFront.position.y = 0;
                planeFront.rotateY( Math.PI );
                walls.add(planeFront);

  