velipso

vec2 grad(ivec2 z) {
  int n = z.x+z.y*11111;
  n = (n<<13)^n;
  n = (n*(n*n*15731+789221)+1376312589)>>16;
  return vec2(cos(float(n)),sin(float(n)));
}

float noise(vec2 p, float seed) {
  p += vec2(cos(seed * 123.456) * 123.456, sin(seed * 456.789) * 456.789);
  ivec2 i = ivec2(floor(p));