noise.js

/*
  This code was taken from here:
  https://github.com/josephg/noisejs
*/

function Grad(x,  y,  z) {
  this.x = x; this.y = y; this.z = z;
}

Grad.prototype.dot2 = function(x,  y) {
  return this.x * x + this.y * y;
};

var grad3 = [new Grad(1, 1, 0), new Grad(-1, 1, 0), new Grad(1, -1, 0), new Grad(-1, -1, 0),
             new Grad(1, 0, 1), new Grad(-1, 0, 1), new Grad(1, 0, -1), new Grad(-1, 0, -1),
             new Grad(0, 1, 1), new Grad(0, -1, 1), new Grad(0, 1, -1), new Grad(0, -1, -1)];

var p = [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];
// To remove the need for index wrapping,  double the permutation table length
var perm = new Array(512);
var gradP = new Array(512);

// This isn't a very good seeding function,  but it works ok. It supports 2^16
// different seed values. Write something better if you need more seeds.
seed = function(seed) {
  if(seed > 0 && seed < 1) {
    // Scale the seed out
    seed  *= 65536;
  }

  seed = Math.floor(seed);
  if(seed < 256) {
    seed |= seed << 8;
  }

  for(var i = 0; i < 256; i++) {
    var v;
    if (i & 1) {
      v = p[i] ^ (seed & 255);
    } else {
      v = p[i] ^ ((seed>>8) & 255);
    }

    perm[i] = perm[i + 256] = v;
    gradP[i] = gradP[i + 256] = grad3[v % 12];
  }
};

seed(0);

function fade(t) {
  // return t * t * t * (t * (t * 6-15)+10);
  return t
}

function lerp(a,  b,  t) {
  return (1-t) * a + t * b;
}

// 2D Perlin Noise
module.exports = function(x,  y) {
  // Find unit grid cell containing point
  var X = Math.floor(x),  Y = Math.floor(y);
  // Get relative xy coordinates of point within that cell
  x = x - X; y = y - Y;
  // Wrap the integer cells at 255 (smaller integer period can be introduced here)
  X = X & 255; Y = Y & 255;

  // Calculate noise contributions from each of the four corners
  var n00 = gradP[X+perm[Y]].dot2(x,  y);
  var n01 = gradP[X+perm[Y+1]].dot2(x,  y-1);
  var n10 = gradP[X+1+perm[Y]].dot2(x-1,  y);
  var n11 = gradP[X+1+perm[Y+1]].dot2(x-1,  y-1);

  // Compute the fade curve value for x
  var u = fade(x);

  // Interpolate the four results
  return lerp(
    lerp(n00,  n10,  u),
    lerp(n01,  n11,  u),
    fade(y));
};