precision mediump float;

#endif

​

varying vec2 pos;

​

const float colourVariance = 0.2;

​

uniform vec3 colourA;

uniform vec3 colourB;

​

uniform float seed;

​

// 2D Random with salt

float random (in vec2 st, in float salt) {

    return fract(sin(dot(st, vec2(12.9898, 78.233) + salt + seed)) * 43758.5453);

}

​

// 2D Noise based on Morgan McGuire @morgan3d

// https://www.shadertoy.com/view/4dS3Wd

float noise (in vec2 st, float scale, float salt) {

  st *= scale;

  vec2 i = floor(st);

  vec2 f = fract(st);

​

  // Four corners in 2D of a tile

  float a = random(i, salt);

  float b = random(i + vec2(1.0, 0.0), salt);

  float c = random(i + vec2(0.0, 1.0), salt);

  float d = random(i + vec2(1.0, 1.0), salt);

​

  // Smooth Interpolation

​

  // Cubic Hermine Curve.  Same as SmoothStep()

  vec2 u = f*f*(3.0-2.0*f);

  // u = smoothstep(0.,1.,f);

​

  // Mix 4 coorners percentages

  return mix(a, b, u.x) +

          (c - a)* u.y * (1.0 - u.x) +

          (d - b) * u.x * u.y;

}

​

void main() {

  // Figure out the colour of a circle. <0.5 = colourA, >=0.5 = colourB

  float n = noise(pos, 10., 0.) * 0.5;

  n += noise(pos, 20., 1.) * 0.25;

  n += noise(pos, 40., 2.) * 0.125;

  float colourToUse = step(0.5, n);

  vec3 colour = mix(colourA, colourB, n);

​

  float varyR = noise(pos, 1., 1.);

  float varyG = noise(pos, 2., 2.);

  float varyB = noise(pos, 3., 3.);

  colour.r += sin(varyR * 6.28) * colourVariance;

  colour.g += sin(varyG * 6.28) * colourVariance;

  colour.b += sin(varyB * 6.28) * colourVariance;

  colour.r += sin(random(pos, 0.0)) * colourVariance;

  colour.g += sin(random(pos, 1.0)) * colourVariance;

  colour.b += sin(random(pos, 2.0)) * colourVariance;

  gl_FragColor = vec4(colour, 1.0);

}

​

​