ik versta da met de polar coordinats nu denk ik

learning/shapes/sdf.frag

@@ -0,0 +1,40 @@
+#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)); }
+
+
+void main() {
+  vec2 st = gl_FragCoord.xy/u_resolution;
+  st.x *= u_resolution.x/u_resolution.y;
+  vec3 color = vec3(0.0,0.0,0.0);
+  float alpha = 1.0;
+
+  float d = 0.;
+  //remaps to -1 - 1;
+  st = st*2.-1.;
+
+  d = length(abs(st)-.3);
+  d = length(min(abs(st)-.3,0.));
+  d = length(max(abs(st)-.3,0.));
+  //color += fract(d*10.);
+  //color += vec3(step(.3,d));
+  //color += vec3(step(.3,d)*step(d,.4));
+  color += vec3(smoothstep(.3,.4,d)*smoothstep(.6,.5,d));
+
+  
+
+  gl_FragColor = vec4(color, alpha);
+}