7_0_circle

Figure 7.2, Code 7.1:

7_0_circle.frag

#version 300 es precision highp float; precision highp int; out vec4 fragColor; uniform float u_time; uniform vec2 u_resolution; uniform vec2 u_mouse; const float PI = 3.14159265359; float circle(vec2 p, vec2 c, float r){ float d = 0.5 + u_mouse.x / u_resolution.x; return pow(dot(p - c, p - c), d) - 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); float interval = 0.3; fragColor.rgb = vec3(contour(circle(pos, vec2(0.0), 1.0), interval)); fragColor.a = 1.0; }

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

float circle(vec2 p, vec2 c, float r){
  float d = 0.5 + u_mouse.x / u_resolution.x;
  return pow(dot(p - c, p - c), d) - 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);
  float interval = 0.3;
  fragColor.rgb = vec3(contour(circle(pos, vec2(0.0), 1.0), interval));
  fragColor.a = 1.0;
}