= texture2D(u_velocity_texture, vT).y;
        float B = texture2D(u_velocity_texture, vB).y;

        float div = .6 * (R - L + T - B);
        gl_FragColor = vec4(div, 0., 0., 1.);
    }
</script>

<script type="x-shader/x-fragment" id="fragShaderPressure">
    precision highp float;
    precision highp sampler2D;

    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D u_pressure_texture