ergence_texture, vUv).x;

        float pressure = (L + R + B + T - divergence) * 0.25;
        pressure += (.2 * text);

        gl_FragColor = vec4(pressure, 0., 0., 1.);
    }
</script>

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