// Gold Noise ?2015 dcerisano@standard3d.com
// - based on the Golden Ratio
// - uniform normalized distribution
// - fastest static noise generator function (also runs at low precision)

float PHI = 1.61803398874989484820459;  // = Golden Ratio   

float gold_noise(in vec2 xy, in float seed){
       return fract(tan(distance(xy*PHI, xy)*seed)*xy.x);
}