ik versta da met de polar coordinats nu denk ik

experiments/test/main.frag

@@ -0,0 +1,31 @@
+#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 circleSDF(vec2 st) { return length(st-.5)*2.; }
+
+void main() {
+  vec2 st = gl_FragCoord.xy/u_resolution;
+  vec3 color = vec3(.0,.0,.0);
+  float alpha = 1.0;
+  float circle = length(st-.5)*2.;
+  float s = u_time/8.;
+  float f_circle = fract((circle-s)*5.);
+  
+  //color += f_circle;
+  color += step(.5,f_circle);
+  gl_FragColor = vec4(color, alpha);
+}