a = 0.0;
  }
  return alpha;
}

vec3 rgbcol(vec3 col) {
  return vec3(col.r/255.0,col.g/255.0,col.b/255.0);
}

vec2 rotate(vec2 v, float a) {
  float s = sin(a);
  float c = cos(a);
  mat2 m = mat2(c, -s, s, c);
  return m * v;
}

vec2 UnityPolarCoordinates (vec2 UV, vec2 Center, float RadialScale, float LengthScale){
  //https://twitter.com/Cyanilux/status/1123950519133908995/photo/1
  vec2 delta = UV - Center;
  float radius = length(delta) * 2. * RadialScale;
  float angle = atan(delta.x, delta.y) * 1.0/