uniform sampler2D uSampler;
uniform vec4 inputPixel;
uniform float time;
varying vec2 vTextureCoord;

#define TAU 6.28318530718
#define MAX_ITER 3

float sine(float x, float t, float f, float a) {
    return a * sin(x * f + t);
}

float cosine(float x, float t, float f, float a) {
    return a * cos(x * f + t);
}

void main()
{
    // uv should be the 0-1 uv of texture...
    vec2 uv = gl_FragCoord.xy / inputPixel.xy;
    vec2 p = uv*7.0-250.0;

    vec2 i = vec2(p);
    float c = 1.0;
    float inten = .003;

    for (int n = 0; n < MAX_ITER; n++)
    {
        i = float(n + 2) * p + vec2(cos(time - i.x) + sin(time + i.y), sin(time - i.y) + cos(time + i.x));
        c += 1.0/length(vec2(p.x / (sin(i.x+time)/inten), p.y / (cos(i.y+time)/inten)));
    }
    c /= float(MAX_ITER);
    c = 1.17-pow(c, 1.4);
    vec3 colour = vec3(pow(abs(c), 8.0));
    colour = clamp(colour, 0.0, clamp(c, 0.3, 0.8));

    colour = colour*0.3;
    vec4 originalColor = texture2D(uSampler, vTextureCoord);
    gl_FragColor = originalColor + vec4(colour, 1.0);
}