Noise3.frag

#ifdef GL_ES
precision highp float;
#endif

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

//---------------------------------------------------------------------

#define SEED 43758.5453123

vec2 random2(vec2 st) {
  st = vec2(dot(st, vec2(127.1, 311.7)),
    dot(st, vec2(269.5, 183.3)));
    #ifdef GL_ES
 	return -1.0 + 2.0 * fract(sin(st));
    #else
        return -1.0 + 2.0 * fract(sin(st) * SEED);
    #endif
}

// Gradient Noise by Inigo Quilez - iq/2013
// https://www.shadertoy.com/view/XdXGW8
float noise(vec2 st) {
  vec2 i = floor(st);
  vec2 f = fract(st);

  vec2 u = f * f * (3.0 - 2.0 * f);

  return mix( mix( dot( random2(i + vec2(0.0, 0.0) ), f - vec2(0.0, 0.0) ),
                   dot( random2(i + vec2(1.0, 0.0) ), f - vec2(1.0, 0.0) ), u.x),
              mix( dot( random2(i + vec2(0.0, 1.0) ), f - vec2(0.0, 1.0) ),
                   dot( random2(i + vec2(1.0, 1.0) ), f - vec2(1.0, 1.0) ), u.x), u.y);
}

float circle(in vec2 _st, in float _radius) {
  vec2 dist = _st - vec2(0.5);
  return 1. - smoothstep(_radius - (_radius * 0.01),
   _radius + (_radius * 0.01),
   dot(dist, dist) * 4.0);
}

float shapeBorder(vec2 st, float radius, float width) {
  return circle(st, radius) - circle(st, radius - width);
}

//---------------------------------------------------------------------

void main() {
  vec2 st = gl_FragCoord.xy / u_resolution.xy;
  st.x *= u_resolution.x/u_resolution.y;
  st.y *= u_resolution.y/u_resolution.x;

  float t = 1.0;
  t *= abs(1.0 - sin(u_time * .35)) * 7.;

  st += noise(st * 1.7) * t;

  vec3 color = vec3(1.0) * shapeBorder(st, noise(st), 7.);
  color += vec3(.7, .7, .7) * smoothstep(.7, .2, noise(st));

  vec2 toCenter = vec2(0.5) - st;
  float angle = atan(toCenter.y, toCenter.x);
  float radius = length(toCenter) * 2.0;

  color.r *= radius;
  color.b *= angle;
  color.g /= toCenter.x;

  gl_FragColor = vec4(color, 1.0);
}