mandelbrot.glsl

float flimit(float n, float low, float high)
{
    return max(min(n, high), low);
}

float fmap(float n, float start1, float stop1, float start2, float stop2)
{
    float newval = (n - start1) / (stop1 - start1) * (stop2 - start2) + start2;

    if (start2 < stop2)
    {
        return flimit(newval, start2, stop2);
    }
    else
    {
        return flimit(newval, stop2, start2);
    }
}

vec3 hsl2rgb( in vec3 c )
{
    vec3 rgb = clamp( abs(mod(c.x*6.0+vec3(0.0,4.0,2.0),6.0)-3.0)-1.0, 0.0, 1.0 );

    return c.z + c.y * (rgb-0.5)*(1.0-abs(2.0*c.z-1.0));
}

float deg2rad(float deg)
{
    return deg * 0.01745329;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
    vec2 uv = fragCoord/iResolution.xy;
    float x = fragCoord.x;
    float y = fragCoord.y;
    
    float time = 80.0;
    float now = abs(sin(iTime / 50.0) * 10.0) - 50.0;
    // float now = iTime;
    // if (now == round(now)) now += 0.25;
    float iter = ((now * now) * 6.0);
    
    float size = fmap(now, 0.0, time, 4.0, 4.0 + time * now) * (now * now * now);
    vec2 offset = vec2(0.23988, 0.510446);
    
    float a = fmap(x, 0.0, iResolution.x, -8.0 / size, 8.0 / size) + offset.x;
    float b = fmap(y, 0.0, iResolution.y, -4.5 / size, 4.5 / size) + offset.y;
    
    float n = 0.0;
    float ca = a;
    float cb = b;
    float z = 0.0;
    
    while (n < iter)
    {
        float aa = a * a - b * b;
        float bb = 2.0 * a * b;
        
        a = aa + ca;
        b = bb + cb;
        
        if (abs(a + b) > 16.0)
        {
            break;
        }
        
        n++;
    }
    
    float hue = sqrt(size / n) * 10.0;
    float bright = sqrt(fmap(n, 0.0, iter, 0.25, 0.75));
    float sat = sqrt(fmap(now, 0.0, now, 0.75, 1.0));
    
    if (n == iter)
    {
        bright = 0.0;
    }
    
    // if (bright >= 0.72) bright = 0.0;
    
    vec3 col = hsl2rgb(vec3(deg2rad(hue), sat, bright));
    
    fragColor = vec4(col, 1.0);
}