4 Cb = texture2D(tSec, vUv);
                c = Ca.rgb * Ca.a + Cb.rgb * Cb.a * (1.0 - Ca.a);
                gl_FragColor= vec4(c, 1.0);

            }
        </script>

		<script id="vertex_shader" type="x-shader/x-vertex">

            varying vec2 vUv;

            void main()
            {
                vUv = uv;
                vec4 mvPosition = modelViewMatrix * vec4( position, 1.0 );
                gl_Position = projectionMatrix * mvPosition;
            }

        </script>
