1_6_hsv2rgb

Code 1.10, Figure 1.12:

1_6_hsv2rgb.frag

#version 300 es precision highp float; out vec4 fragColor; uniform float u_time; uniform vec2 u_resolution; const float PI = 3.1415926; float atan2(float y, float x){ if (x == 0.0){ return sign(y) * PI / 2.0; } else { return atan(y, x); } } vec2 xy2pol(vec2 xy){ return vec2(atan2(xy.y, xy.x), length(xy)); } vec2 pol2xy(vec2 pol){ return pol.y * vec2(cos(pol.x), sin(pol.x)); } vec3 hsv2rgb(vec3 c){ // fork from https://www.shadertoy.com/view/MsS3Wc vec3 rgb = clamp(abs(mod(c.x * 6.0 + vec3(0.0, 4.0, 2.0), 6.0) - 3.0) - 1.0, 0.0, 1.0); return c.z * mix(vec3(1.0), rgb, c.y); } void main(){ vec2 pos = gl_FragCoord.xy / u_resolution.xy; pos = 2.0 * pos.xy - vec2(1.0); pos = xy2pol(pos); pos.x = mod(0.5 * pos.x / PI, 1.0); fragColor.rgb = hsv2rgb(vec3(pos, 1.0)); fragColor.a = 1.0; }

#version 300 es
precision highp float;
out vec4 fragColor;
uniform float u_time;
uniform vec2 u_resolution;
const float PI = 3.1415926;

float atan2(float y, float x){
  if (x == 0.0){
    return sign(y) * PI / 2.0;
  } else {
    return atan(y, x);
  }
}

vec2 xy2pol(vec2 xy){
  return vec2(atan2(xy.y, xy.x), length(xy));
}

vec2 pol2xy(vec2 pol){
  return pol.y * vec2(cos(pol.x), sin(pol.x));
}

vec3 hsv2rgb(vec3 c){ // fork from https://www.shadertoy.com/view/MsS3Wc
  vec3 rgb = clamp(abs(mod(c.x * 6.0 + vec3(0.0, 4.0, 2.0), 6.0) - 3.0) - 1.0, 0.0, 1.0);
  return c.z * mix(vec3(1.0), rgb, c.y);
}

void main(){
  vec2 pos = gl_FragCoord.xy / u_resolution.xy;
  pos = 2.0 * pos.xy - vec2(1.0);
  pos = xy2pol(pos);
  pos.x = mod(0.5 * pos.x / PI, 1.0);
  fragColor.rgb = hsv2rgb(vec3(pos, 1.0));
  fragColor.a = 1.0;
}