宏、常量、循环与函数

#define PETALS 6
#define WARM 1
const float TAU = 6.283185;
float disk(vec2 p) {
  return 1.0 - smoothstep(0.1, 0.108, length(p));
}

void main() {
  vec2 p = (gl_FragCoord.xy - 0.5 * uResolution) / min(uResolution.x, uResolution.y);
  float flower = 0.0;
  for (int i = 0; i < PETALS; i++) {
    float a = float(i) * TAU / float(PETALS);
    vec2 center = vec2(cos(a), sin(a)) * 0.2;
    flower = max(flower, disk(p - center));
  }
  #if WARM
    vec3 ink = vec3(0.96, 0.43, 0.30);
  #else
    vec3 ink = vec3(0.48, 0.83, 0.69);
  #endif
  vec3 color = mix(vec3(0.06, 0.10, 0.14), ink, flower);
  gl_FragColor = vec4(color, 1.0);
}