glsl vjaying experiment

test.glsl

$HEADER$

float PI = 3.1415926535;
uniform vec2 resolution;
uniform float time;

vec2 rotate(vec2 pos, float angle, vec2 center){
  pos -= center;
  pos *= mat2(cos(angle), sin(-angle), sin(angle), cos(angle));
  pos += center;
  return pos;
}

vec2 scale(vec2 pos, float scale, vec2 center){
  pos -= center;
  pos *= scale;
  pos += center;
  return pos;
}

float nsin(float f){
  return .5 + .5 * sin(f);
}

float ncos(float f){
  return .5 + .5 * cos(f);
}

vec3 f1(vec2 pos, float time) {
  vec2 center = scale(vec2(nsin(time), ncos(time)), .5, vec2(.5));
  vec3 c = vec3(1.0);

  float d = distance(pos, center);
  c *= step(.9, 1. - d);

  return c;
}

vec3 ab(vec2 pos, float time){
  vec2 offset_ = vec2(2. / resolution.x, 0.);
  return vec3(
    f1(pos - offset_, time) * vec3(2.0, 1.0, 0.0) +
    f1(pos,           time) * vec3(1.0, 1.0, 1.0) +
    f1(pos + offset_, time) * vec3(0.0, 1.0, 2.0)
  ) / 3.0;
}

vec3 blur(vec2 pos, float time){
  vec3 c = vec3(0., 0., 0.);
  float steps = 5.0;
  for (float t=0.0; t <= steps; t += 1.0){
    c += ab(pos, time+t/100.);
  }
  return c/ steps;
}

void main(void)
{
  vec2 pos = gl_FragCoord.xy / resolution;

  vec3 c = blur(pos, time);

  gl_FragColor = vec4(
      c.r,
      c.g,
      c.b,
      1.0
  );
}