;
    uniform sampler2D u_divergence_texture;
    uniform sampler2D u_text_texture;

    void main () {

        float text = texture2D(u_text_texture, vec2(vUv.x, 1. - vUv.y)).r;

        float L = texture2D(u_pressure_texture, vL).x;
        float R = texture2D(u_pressure_texture, vR).x;
        float T = texture2D(u_pressure_texture, vT).x;
        float B = texture2D(u_pressure_texture, vB).x;
        float C = texture2D(u_pressure_texture, vUv).x;
        float divergence = texture2D(u_div