7_2_varyDist

Code 7.3, Figure 7.9:

7_2_varyDist.frag

#version 300 es precision highp float; precision highp int; out vec4 fragColor; uniform float u_time; uniform vec2 u_resolution; const float PI = 3.14159265359; float length2(vec2 p){ float t = mod(u_time, 3.0); p = abs(p); return t < 1.0 ? length(p): t < 2.0 ? dot(p, vec2(1.0)): max(p.x, p.y); } float circle(vec2 p, vec2 c, float r){ return length2(p - c) - r; } vec3 contour(float v, float interval){ return abs(v) < 0.01 ? vec3(0.0): mod(v, interval) < 0.01 ? vec3(1.0): mix(vec3(0, 0, 1), vec3(1, 0, 0), atan(v) / PI + 0.5); } void main(){ vec2 pos = (2.0 * gl_FragCoord.xy -u_resolution.xy)/ min(u_resolution.x, u_resolution.y); fragColor.rgb = vec3(contour(circle(pos, vec2(0.0), 1.0), 0.1)); fragColor.a = 1.0; }

#version 300 es
precision highp float;
precision highp int;
out vec4 fragColor;
uniform float u_time;
uniform vec2 u_resolution;
const float PI = 3.14159265359;

float length2(vec2 p){
  float t = mod(u_time, 3.0);
  p = abs(p);
  return t < 1.0 ? length(p):
    t < 2.0 ? dot(p, vec2(1.0)):
    max(p.x, p.y);
}

float circle(vec2 p, vec2 c, float r){
  return length2(p - c) - r;
}

vec3 contour(float v, float interval){
  return abs(v) < 0.01 ? vec3(0.0):
  mod(v, interval) < 0.01 ? vec3(1.0):
  mix(vec3(0, 0, 1), vec3(1, 0, 0), atan(v) / PI + 0.5);
}

void main(){
  vec2 pos = (2.0 * gl_FragCoord.xy -u_resolution.xy)/ min(u_resolution.x, u_resolution.y);
  fragColor.rgb = vec3(contour(circle(pos, vec2(0.0), 1.0), 0.1));
  fragColor.a = 1.0;
}