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Daily Creative Coding

元「30 min. Processing」。毎日、Creative Codingします。

【GLSL】多角形

See the Pen polygon by aadebdeb (@aadebdeb) on CodePen.

  #define PI 3.14159265359
  #define TWO_PI PI * 2.0

precision mediump float;

uniform float u_time;
uniform vec2 u_mouse;
uniform vec2 u_resolution;

float polygon(vec2 center, vec2 st, float radius, int n) {
  vec2 pos = st - center;
  float a = atan(pos.x, pos.y) + PI;
  float r = TWO_PI / float(n);

  float d = cos(floor(.5 + a / r) * r - a) * length(pos);

  return smoothstep(radius * 0.95, radius, d) - smoothstep(radius, radius * 1.05, d);
}

void main(void) {
  float m = min(u_resolution.x, u_resolution.y);
  vec2 st = gl_FragCoord.xy / m;
  st = st * 2.0 - u_resolution / m;

  vec3 v = vec3(0.82, 0.945, 0.8);
  v = mix(v, vec3(0.714, 0.098, 0.447),  polygon(vec2(-0.33, -0.33), st, 0.15, 3));
  v = mix(v, vec3(0.714, 0.098, 0.447),  polygon(vec2(0.33, -0.33), st, 0.15, 4));
  v = mix(v, vec3(0.714, 0.098, 0.447),  polygon(vec2(-0.33, 0.33), st, 0.15, 5));
  v = mix(v, vec3(0.714, 0.098, 0.447),  polygon(vec2(0.33, 0.33), st, 0.15, 6));

  gl_FragColor = vec4(v, 1.0);
}
f:id:aa_debdeb:20170418090627p:plain