feigenbaum

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    float lambda = fragCoord.x/iResolution.x * 4.0;

    float t = fragCoord.y/iResolution.y;

    for (int i = 0; i < 1000; i++) {
        t = lambda * t * (1.0 - t);
    }

    float col = 0.0;
    float lb = fragCoord.y/iResolution.y;
    float ub = (fragCoord.y + 1.0)/iResolution.y;
    for (int i = 0; i < 256; i++) {
        t = lambda * t * (1.0 - t);
        if (lb < t && t < ub) {
            col += 1.0 / 256.0;
        }
    }

    col = sqrt(col);
    col = sqrt(col);

    // Output to screen
    fragColor = vec4(col,col,col,1.0);
}