1_5_polarRot

Code 1.9, Figure 1.11:

1_5_polarRot.frag

#version 300 es precision highp float; out vec4 fragColor; uniform float u_time; uniform vec2 u_resolution; const float PI = 3.14159265; float atan2(float y, float x){ if (x == 0.0){ return sign(y) * PI / 2.0; } else { return atan(y, x); } } vec2 xy2pol(vec2 xy){ return vec2(atan2(xy.y, xy.x), length(xy)); } vec2 pol2xy(vec2 pol){ return pol.y * vec2(cos(pol.x), sin(pol.x)); } vec3 tex(vec2 st){ float time = 0.2 * u_time; vec3 circ = vec3(pol2xy(vec2(time, 0.5)) + 0.5, 1.0); vec3[3] col3 = vec3[]( circ.rgb, circ.gbr, circ.brg ); st.s = st.s / PI + 1.0; st.s += time; int ind = int(st.s); vec3 col = mix(col3[ind % 2], col3[(ind + 1) % 2], fract(st.s)); return mix(col3[2], col, st.t); } void main(){ vec2 pos = gl_FragCoord.xy / u_resolution.xy; pos = 2.0 * pos - vec2(1.0); pos = xy2pol(pos); fragColor = vec4(tex(pos), 1.0); }

#version 300 es
precision highp float;
out vec4 fragColor;
uniform float u_time;
uniform vec2 u_resolution;
const float PI = 3.14159265;

float atan2(float y, float x){
  if (x == 0.0){
    return sign(y) * PI / 2.0;
  } else {
    return atan(y, x);
  }
}

vec2 xy2pol(vec2 xy){
  return vec2(atan2(xy.y, xy.x), length(xy));
}

vec2 pol2xy(vec2 pol){
  return pol.y * vec2(cos(pol.x), sin(pol.x));
}

vec3 tex(vec2 st){
  float time = 0.2 * u_time;
  vec3 circ = vec3(pol2xy(vec2(time, 0.5)) + 0.5, 1.0);
  vec3[3] col3 = vec3[](
    circ.rgb, circ.gbr, circ.brg
  );
  st.s = st.s / PI + 1.0;
  st.s += time;
  int ind = int(st.s);
  vec3 col = mix(col3[ind % 2], col3[(ind + 1) % 2], fract(st.s));
  return mix(col3[2], col, st.t);
}

void main(){
  vec2 pos = gl_FragCoord.xy / u_resolution.xy;
  pos = 2.0 * pos - vec2(1.0);
  pos = xy2pol(pos);    
  fragColor = vec4(tex(pos), 1.0);
}