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varying vec4 v_position;
uniform vec2 u_resolution;
uniform float u_time;
uniform float u_mouse;
#define MAX_ITERATIONS 100
vec2 cmul(vec2 a, vec2 b) {
return vec2(a.x*b.x - a.y*b.y, a.x*b.y + a.y*b.x);
}
vec2 cdiv(vec2 a, vec2 b) {
float denominator = b.x*b.x + b.y*b.y;
if (denominator == 0.) return a;
return cmul(a, vec2(b.x, -b.y)) / denominator;
}
vec2 cpow(vec2 z, float n) {
float r = length(z);
float theta = atan(z.y, z.x);
return pow(r, n) * vec2(cos(n * theta), sin(n * theta));
}
float fabs(float a) { return a > 0. ? a : -a; }
void main() {
float time = mod(0.5 + mod(u_time * 1000.0, 100000.0) / 10000.0, 2.);
float ratio = u_resolution.x / u_resolution.y;
vec2 pos = v_position.xy/vec2(1.0, ratio);
vec2 prevZ;
vec2 z = 2.0 * (pos - vec2(0., 0.));
int iterations = 0;
for (int i = 0; i < MAX_ITERATIONS; i++) {
prevZ = z;
vec2 value = cpow(z, 3.0) + vec2(1., 0.);
vec2 value_der = 3.0 * cpow(z, 2.0);
z = z - time * cdiv(value, value_der);
iterations++;
if (fabs(z.x - prevZ.x) < 0.001) break;
}
float val = float(iterations) * 10.0 / float(MAX_ITERATIONS);
float g = val * 0.5;
float b = val * 0.8;
gl_FragColor = vec4(0.0, g, b, val);
}
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