/*jshint bitwise:false */
/**
* https://gist.github.com/304522
* Ported from Stefan Gustavson's java implementation
* http://staffwww.itn.liu.se/~stegu/simplexnoise/simplexnoise.pdf
* Read Stefan's excellent paper for details on how this code works.
*
* @author Sean McCullough banksean@gmail.com
*
* You can pass in a random number generator object if you like.
* It is assumed to have a random() method.
*/

/**
 * @namespace
 */

var SimplexNoise = {};

SimplexNoise.grad3 = [[1,1,0],[-1,1,0],[1,-1,0],[-1,-1,0],[1,0,1],[-1,0,1],[1,0,-1],[-1,0,-1],[0,1,1],[0,-1,1],[0,1,-1],[0,-1,-1]];
SimplexNoise.p = [];
SimplexNoise.perm = [];
// A lookup table to traverse the simplex around a given point in 4D.
// Details can be found where this table is used, in the 4D noise method.
SimplexNoise.simplex = [
  [0,1,2,3],[0,1,3,2],[0,0,0,0],[0,2,3,1],[0,0,0,0],[0,0,0,0],[0,0,0,0],[1,2,3,0],
  [0,2,1,3],[0,0,0,0],[0,3,1,2],[0,3,2,1],[0,0,0,0],[0,0,0,0],[0,0,0,0],[1,3,2,0],
  [0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],
  [1,2,0,3],[0,0,0,0],[1,3,0,2],[0,0,0,0],[0,0,0,0],[0,0,0,0],[2,3,0,1],[2,3,1,0],
  [1,0,2,3],[1,0,3,2],[0,0,0,0],[0,0,0,0],[0,0,0,0],[2,0,3,1],[0,0,0,0],[2,1,3,0],
  [0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],[0,0,0,0],
  [2,0,1,3],[0,0,0,0],[0,0,0,0],[0,0,0,0],[3,0,1,2],[3,0,2,1],[0,0,0,0],[3,1,2,0],
  [2,1,0,3],[0,0,0,0],[0,0,0,0],[0,0,0,0],[3,1,0,2],[0,0,0,0],[3,2,0,1],[3,2,1,0]];

SimplexNoise.config = function(r) {

var i, p = SimplexNoise.p, perm = SimplexNoise.perm;

if (typeof r === 'undefined') {
    r = Math;
  }

for (i = 0; i < 256; i += 1) {
    SimplexNoise.p[i] = Math.floor(r.random() * 256);
  }
  // To remove the need for index wrapping, double the permutation table length
  for(i = 0; i < 512; i += 1) {
    perm[i] = p[i & 255];
  }
};

SimplexNoise.noise = function(xin, yin) {

var grad3 = SimplexNoise.grad3;
  var p = SimplexNoise.p;
  var perm = SimplexNoise.perm;
  var simplex = SimplexNoise.simplex;

if (!p.length) {
    SimplexNoise.config();
  }

var n0, n1, n2; // Noise contributions from the three corners

// Skew the input space to determine which simplex cell we're in
  var F2 = 0.5 * (Math.sqrt(3.0) - 1.0);
  var s = (xin + yin) * F2; // Hairy factor for 2D
  var i = Math.floor(xin + s);
  var j = Math.floor(yin + s);
  var G2 = (3.0 -Math.sqrt(3.0)) / 6.0;
  var t = (i + j) * G2;
  var X0 = i - t; // Unskew the cell origin back to (x,y) space
  var Y0 = j - t;
  var x0 = xin - X0; // The x,y distances from the cell origin
  var y0 = yin - Y0;

// For the 2D case, the simplex shape is an equilateral triangle.
  // Determine which simplex we are in.
  var i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
  if (x0 > y0) { i1 = 1; j1 = 0; } // lower triangle, XY order: (0,0)->(1,0)->(1,1)
  else { i1 = 0; j1 = 1; }      // upper triangle, YX order: (0,0)->(0,1)->(1,1)
  // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
  // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
  // c = (3-sqrt(3))/6
  var x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
  var y1 = y0 - j1 + G2;
  var x2 = x0 - 1.0 + 2.0 * G2; // Offsets for last corner in (x,y) unskewed coords
  var y2 = y0 - 1.0 + 2.0 * G2;

// Work out the hashed gradient indices of the three simplex corners
  var ii = i & 255;
  var jj = j & 255;
  var gi0 = this.perm[ii + this.perm[jj]] % 12;
  var gi1 = this.perm[ii + i1 + this.perm[jj + j1]] % 12;
  var gi2 = this.perm[ii + 1 + this.perm[jj + 1]] % 12;

// Calculate the contribution from the three corners
  var t0 = 0.5 - x0 * x0 - y0 * y0;
  if (t0 < 0) {
    n0 = 0.0;
  } else {
    t0 *= t0;
    n0 = t0 * t0 * this.dot(this.grad3[gi0], x0, y0);  // (x,y) of grad3 used for 2D gradient
  }
  var t1 = 0.5 - x1 * x1 - y1 * y1;
  if (t1 < 0) {
    n1 = 0.0;
  } else {
    t1 *= t1;
    n1 = t1 * t1 * this.dot(this.grad3[gi1], x1, y1);
  }
  var t2 = 0.5 - x2 * x2 - y2 * y2;
  if (t2 < 0) {
    n2 = 0.0;
  } else {
    t2 *= t2;
    n2 = t2 * t2 * this.dot(this.grad3[gi2], x2, y2);
  }
  // Add contributions from each corner to get the final noise value.
  // The result is scaled to return values in the interval [-1,1].
  return 70.0 * (n0 + n1 + n2);

};

SimplexNoise.dot = function(g, x, y) {
  return g[0] * x + g[1] * y;
};

module.exports = SimplexNoise;

src/quietriot.js

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