computershader.glsl

/* ported from humanshader.com; paste into shadertoy */
void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    float x = fragCoord.x / iResolution.x * 70.0;
    float y = (iResolution.y - fragCoord.y) / iResolution.y * 39.0;
    float u = x - 36.0;
    float v = 18.0 - y;
    float h = u*u+v*v;
    float R, G, B;
    if (h < 200.0) {
        R = 420.0;
        B = 520.0;
        float t = 5000.0 + 8.0 * h;
        float p = (t * u) / 100.0;
        float q = (t * v) / 100.0;
        float s = 2.0 * q;
        float w = (1000.0 + p - s) / 100.0 + 8.0;
        if (w > 0.0) R = R + w*w;
        float o = s + 2200.0;
        R = R * o / 10000.0;
        B = B * o / 10000.0;
        if (p > -q) {
            w = (p + q) / 10.0;
            R = R + w;
            B = B + w;
        }
    } else if (v < 0.0) {
        R = 150.0 + 2.0 * v;
        B = 50.0;
        float p = h + 8.0 * v * v;
        float c = 240.0 * (-v) - p;
        if (c > 1200.0) {
            float o = (6.0 * c) / 10.0;
            o = c * (1500.0 - o);
            o = o / 100.0 - 8360.0;
            R = R * o / 1000.0;
            B = B * o / 1000.0;
        }
        float r = c + u * v;
        float d = 3200.0 - h - 2.0 * r;
        if (d > 0.0) R = R + d;
    } else {
        float c = x + 4.0 * y;
        R = 132.0 + c;
        B = 192.0 + c;
    }

    if (R > 255.0) R = 255.0;
    if (B > 255.0) B = 255.0;
    G = (7.0 * R + 3.0 * B) / 10.0;

    // Output to screen
    fragColor = vec4(R/255.0, G/255.0, B/255.0, 1.0);
}