;
        gl_FragColor.a = 1.;
    }
</script>

<script type="x-shader/x-fragment" id="fragShaderDivergence">
    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_velocity_texture;

    void main () {
        float L = texture2D(u_velocity_texture, vL).x;
        float R = texture2D(u_velocity_texture, vR).x;
        float T 