​

varying vec2 pos;

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const float maxJitter = 0.1;

const float maxMvmt = 0.05;

const float cellSize = 0.1;

const float noiseOffset = 10.0;

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uniform vec3 peakColour;

uniform vec3 troughColour;

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uniform float seconds;

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uniform float seed;

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float rand(vec2 co, float salt){

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

}

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vec2 pointPos(float i, float j) {

  float offX = cos(seconds + i * 3.14) * maxMvmt;

  float offY = sin(seconds + j * 3.14) * maxMvmt;

  float x = i + rand(vec2(i, j) + noiseOffset, 0.0) * maxJitter + offX;

  float y = j + rand(vec2(i, j) + noiseOffset, 1.0) * maxJitter + offY;

  return vec2(x, y);

}

​

void main() {

  float minDist = 2.0;

  vec2 currentCell = floor(pos/cellSize) * cellSize;

  // Find min dist to one of the surrounding grid points

  for(float i = -2.0; i <= 2.0; i ++) {

    for(float j = -2.0; j <= 2.0; j ++) {

      float cellX = currentCell.x + (i * cellSize);

      float cellY = currentCell.y + (j * cellSize);

      vec2 point = pointPos(cellX, cellY);

      float dist = distance(pos, point)/cellSize;

      minDist = min(dist, minDist);

    }

  }

  minDist = minDist * minDist;

  vec3 colour = mix(troughColour, peakColour, minDist);

  // colour = vec3(currentCell.xy, 1.0);

  gl_FragColor = vec4(colour, 0.5);

}

​

​