9_1_boolOp2d

Figure 9.2:

9_1_boolOp2d.frag

#version 300 es precision highp float; out vec4 fragColor; uniform float u_time; uniform vec2 u_resolution; const float PI = 3.14159265359; float rectSDF(vec2 p, vec2 c, vec2 d){ p = abs(p - c); return length(max(p - d, vec2(0.0))) + min(max(p.x - d.x, p.y - d.y), 0.0); } float circleSDF(vec2 p, vec2 c, float r){ return length(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)/ u_resolution.yy; float v1 = circleSDF(pos, vec2(0.2), 0.4); float v2 = rectSDF(pos, vec2(-0.2), vec2(0.4)); float v = int(u_time) % 3 == 0 ? max(v1, v2): int(u_time)% 3 == 1 ? min(v1, v2): max(v1, -v2); fragColor = vec4(contour(v, 0.1), 1.0); }

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

float rectSDF(vec2 p, vec2 c, vec2 d){
  p = abs(p - c);
  return length(max(p - d, vec2(0.0))) + min(max(p.x - d.x, p.y - d.y), 0.0);
}

float circleSDF(vec2 p, vec2 c, float r){
  return length(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)/ u_resolution.yy;
  float v1 = circleSDF(pos, vec2(0.2), 0.4);
  float v2 = rectSDF(pos, vec2(-0.2), vec2(0.4));
  float v = int(u_time) % 3 == 0 ? max(v1, v2):
    int(u_time)% 3 == 1 ? min(v1, v2):
    max(v1, -v2);
  fragColor = vec4(contour(v, 0.1), 1.0);
}