ik versta da met de polar coordinats nu denk ik

learning/shapes/polar_shapes.frag

@@ -0,0 +1,39 @@
+#ifdef GL_ES
+precision mediump float;
+#endif
+uniform vec2 u_resolution;
+uniform vec2 u_mouse;
+uniform float u_time;
+
+#define PI 3.14159265359
+
+const vec3 uAColor = vec3(.5,.5,.5);
+const vec3 uBColor = vec3(.5,.5,.5);
+const vec3 uCColor = vec3(1.,1.,1.);
+const vec3 uDColor = vec3(.0,.33,.67);
+
+//get colors from http://dev.thi.ng/gradients/
+vec3 cosPalette(float t) { return uAColor + uBColor*cos(6.28318*(uCColor*t+uDColor)); }
+
+float stroke(in float x_coor, float s, float width){
+  float d = step(s,x_coor+width*.5)-step(s,x_coor-width*.5);
+  return clamp(d, 0.,1.);
+}
+
+void main() {
+  vec2 st = gl_FragCoord.xy/u_resolution;
+  vec3 color = vec3(0.0,0.0,0.0);
+  float alpha = 1.0;
+  vec2 pos = vec2(.5)-st;
+  float r = length(pos)*2.;
+  float a = atan(pos.y,pos.x);
+  float f = sin(a*3.);
+  f = abs(cos(a*3.));
+  f = abs(cos(a*2.5))*.5+.3;
+  f = abs(cos(a*12.)*sin(a*3.))*.8+.1;
+  f = smoothstep(-.5,.8,cos(a*10.))*.2+.5;
+  color += 1.-stroke(f, 1.,.4);
+  
+
+  gl_FragColor = vec4(color, alpha);
+}