// IMPLEMENTATION OF IMPROVED NOISE - COPYRIGHT 2002 KEN PERLIN.

const p = [];

const permutation = [151,160,137,91,90,15,

131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,

190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,

88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,

77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,

102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,

135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,

5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,

223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,

129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,

251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,

49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,

138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180];

for (let i = 0; i < 256 ; i++) 

  p[256+i] = p[i] = permutation[i]; 

function noise(x, y, z) {

  const X = Math.floor(x) & 255,                  

        Y = Math.floor(y) & 255,                  

        Z = Math.floor(z) & 255;

  x -= Math.floor(x);                                

  y -= Math.floor(y);                               

  z -= Math.floor(z);

  const u = fade(x),                               

        v = fade(y),                                

        w = fade(z);

  const A = p[X  ]+Y, AA = p[A]+Z, AB = p[A+1]+Z,      

      B = p[X+1]+Y, BA = p[B]+Z, BB = p[B+1]+Z;      

  return lerp(w, lerp(v, lerp(u, grad(p[AA  ], x  , y  , z   ),  

                                  grad(p[BA  ], x-1, y  , z   )), 

                          lerp(u, grad(p[AB  ], x  , y-1, z   ),   

                                  grad(p[BB  ], x-1, y-1, z   ))), 

                  lerp(v, lerp(u, grad(p[AA+1], x  , y  , z-1 ),   

                                  grad(p[BA+1], x-1, y  , z-1 )),  

                          lerp(u, grad(p[AB+1], x  , y-1, z-1 ),

                                  grad(p[BB+1], x-1, y-1, z-1 ))));

}

function fade(t) { 

  return t * t * t * (t * (t * 6 - 15) + 10); 

}

function lerp(t, a, b) { 

  return a + t * (b - a); 

}

function grad(hash, x, y, z) {

  const h = hash & 15;                      

  const u = h<8 ? x : y,                 

        v = h<4 ? y : h==12||h==14 ? x : z;

  return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);

}

const canvas = document.body.appendChild(document.createElement('canvas'));

const c = canvas.getContext('2d');

canvas.width = canvas.height = 200;

c.fillStyle = 'black';

c.fillRect(0, 0, canvas.width, canvas.height);

const pix = c.createImageData(canvas.width, canvas.height);

const freq = 1 / 20;

let inc = 0;

let z = 0;

function loop() {

  z += 0.02;

  inc = 0;

  for (var y = 0; y < canvas.height; y++) {

    for (var x = 0; x < canvas.width; x++) {

      var col = parseInt(Math.abs(noise(x * freq, y * freq, z)) * 500);

      pix.data[inc++] = col;

      pix.data[inc++] = col;

      pix.data[inc++] = col;

      pix.data[inc++] = 255;

    }

  }

  c.putImageData(pix, 0, 0);

  window.requestAnimationFrame(loop);

}

loop();