gistfile1.txt

#ifdef GL_ES
precision mediump float;
#endif
 
uniform float time;
uniform vec2 resolution;
 
const int k = 3;
const int stripes = 30;

vec3 hsvToRgb(float h, float s, float v) {
	float c = s * v;
	float hScaled = h / 60.0;
	int index = int(h);
	float x = c * (1.0 - abs(mod(hScaled, 2.0) - 1.0));
	float m = v - c;
	vec3 rgb = vec3(m);
	if (index == 0) {
		rgb += vec3(c, x, 0);
	} else if (index == 1) {
		rgb += vec3(x, c, 0);
	} else if (index == 2) {
		rgb += vec3(0, c, x);
	} else if (index == 3) {
		rgb += vec3(0, x, c);
	} else if (index == 4) {
		rgb += vec3(x, 0, c);
	} else if (index == 5) {
		rgb += vec3(c, 0, x);
	}
		
	return rgb;
}

void main( void ) {
	float PI = 4.0 * atan(1.0);
 
	vec2 res2 = resolution/2.0;
	float phase = 2.0*PI*time/3.0;
	vec2 xy = (gl_FragCoord.xy - res2);
	float theta = atan(xy.y, xy.x);
	float r = log(length(xy*xy));
	vec3 c = vec3(0.0);
	for (int t = 0; t < k; t++) {
		float tScaled = PI*float(t)/float(k);
		float ct = cos(tScaled);
		float st = sin(tScaled);
		//c+=cos((theta*ct-r*st)*float(stripes)+phase);
		// use the following line for cartesian crystals:  
		vec3 col = hsvToRgb(2.0*degrees(tScaled), 1.0, 1.0);
		col *= cos((xy.x*ct+xy.y*st)*2.0*PI*float(stripes)/resolution.x-phase);
		col += 1.0;
		col /= 2.0;
		c += col;  
	}
	c /= float(k);
	gl_FragColor = vec4(c, 1.0);
}