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  1.  
  2. /**********************************************************************************/
  3. /**********************************************************************************/
  4.  
  5. /*
  6.  * A speed-improved perlin and simplex noise algorithms for 2D.
  7.  *
  8.  * Based on example code by Stefan Gustavson (stegu@itn.liu.se).
  9.  * Optimisations by Peter Eastman (peastman@drizzle.stanford.edu).
  10.  * Better rank ordering method by Stefan Gustavson in 2012.
  11.  * Converted to Javascript by Joseph Gentle.
  12.  *
  13.  * Version 2012-03-09
  14.  *
  15.  * This code was placed in the public domain by its original author,
  16.  * Stefan Gustavson. You may use it as you see fit, but
  17.  * attribution is appreciated.
  18.  *
  19.  */
  20.  
  21. (function(global){
  22.   var module = global.Noise = {};
  23.  
  24.   function Grad(x, y, z) {
  25.     this.x = x; this.y = y; this.z = z;
  26.   }
  27.  
  28.   Grad.prototype.dot2 = function(x, y) {
  29.     return this.x*x + this.y*y;
  30.   };
  31.  
  32.   Grad.prototype.dot3 = function(x, y, z) {
  33.     return this.x*x + this.y*y + this.z*z;
  34.   };
  35.  
  36.   var grad3 = [new Grad(1,1,0),new Grad(-1,1,0),new Grad(1,-1,0),new Grad(-1,-1,0),
  37.                new Grad(1,0,1),new Grad(-1,0,1),new Grad(1,0,-1),new Grad(-1,0,-1),
  38.                new Grad(0,1,1),new Grad(0,-1,1),new Grad(0,1,-1),new Grad(0,-1,-1)];
  39.  
  40.   var p = [151,160,137,91,90,15,
  41.   131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
  42.   190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
  43.   88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
  44.   77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
  45.   102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
  46.   135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
  47.   5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
  48.   223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
  49.   129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
  50.   251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
  51.   49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
  52.   138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180];
  53.   // To remove the need for index wrapping, double the permutation table length
  54.   var perm = new Array(512);
  55.   var gradP = new Array(512);
  56.  
  57.   // This isn't a very good seeding function, but it works ok. It supports 2^16
  58.   // different seed values. Write something better if you need more seeds.
  59.   module.seed = function(seed) {
  60.     if(seed > 0 && seed < 1) {
  61.       // Scale the seed out
  62.       seed *= 65536;
  63.     }
  64.  
  65.     seed = Math.floor(seed);
  66.     if(seed < 256) {
  67.       seed |= seed << 8;
  68.     }
  69.  
  70.     for(var i = 0; i < 256; i++) {
  71.       var v;
  72.       if (i & 1) {
  73.         v = p[i] ^ (seed & 255);
  74.       } else {
  75.         v = p[i] ^ ((seed>>8) & 255);
  76.       }
  77.  
  78.       perm[i] = perm[i + 256] = v;
  79.       gradP[i] = gradP[i + 256] = grad3[v % 12];
  80.     }
  81.   };
  82.  
  83.   module.seed(Date.now());
  84.   //module.seed(0);
  85.  
  86.   /*
  87.   for(var i=0; i<256; i++) {
  88.     perm[i] = perm[i + 256] = p[i];
  89.     gradP[i] = gradP[i + 256] = grad3[perm[i] % 12];
  90.   }*/
  91.  
  92.   // Skewing and unskewing factors for 2, 3, and 4 dimensions
  93.   var F2 = 0.5*(Math.sqrt(3)-1);
  94.   var G2 = (3-Math.sqrt(3))/6;
  95.  
  96.   var F3 = 1/3;
  97.   var G3 = 1/6;
  98.  
  99.   // 2D simplex noise
  100.   module.simplex2 = function(xin, yin) {
  101.     var n0, n1, n2; // Noise contributions from the three corners
  102.     // Skew the input space to determine which simplex cell we're in
  103.     var s = (xin+yin)*F2; // Hairy factor for 2D
  104.     var i = Math.floor(xin+s);
  105.     var j = Math.floor(yin+s);
  106.     var t = (i+j)*G2;
  107.     var x0 = xin-i+t; // The x,y distances from the cell origin, unskewed.
  108.     var y0 = yin-j+t;
  109.     // For the 2D case, the simplex shape is an equilateral triangle.
  110.     // Determine which simplex we are in.
  111.     var i1, j1; // Offsets for second (middle) corner of simplex in (i,j) coords
  112.     if(x0>y0) { // lower triangle, XY order: (0,0)->(1,0)->(1,1)
  113.       i1=1; j1=0;
  114.     } else {    // upper triangle, YX order: (0,0)->(0,1)->(1,1)
  115.       i1=0; j1=1;
  116.     }
  117.     // A step of (1,0) in (i,j) means a step of (1-c,-c) in (x,y), and
  118.     // a step of (0,1) in (i,j) means a step of (-c,1-c) in (x,y), where
  119.     // c = (3-sqrt(3))/6
  120.     var x1 = x0 - i1 + G2; // Offsets for middle corner in (x,y) unskewed coords
  121.     var y1 = y0 - j1 + G2;
  122.     var x2 = x0 - 1 + 2 * G2; // Offsets for last corner in (x,y) unskewed coords
  123.     var y2 = y0 - 1 + 2 * G2;
  124.     // Work out the hashed gradient indices of the three simplex corners
  125.     i &= 255;
  126.     j &= 255;
  127.     var gi0 = gradP[i+perm[j]];
  128.     var gi1 = gradP[i+i1+perm[j+j1]];
  129.     var gi2 = gradP[i+1+perm[j+1]];
  130.     // Calculate the contribution from the three corners
  131.     var t0 = 0.5 - x0*x0-y0*y0;
  132.     if(t0<0) {
  133.       n0 = 0;
  134.     } else {
  135.       t0 *= t0;
  136.       n0 = t0 * t0 * gi0.dot2(x0, y0);  // (x,y) of grad3 used for 2D gradient
  137.     }
  138.     var t1 = 0.5 - x1*x1-y1*y1;
  139.     if(t1<0) {
  140.       n1 = 0;
  141.     } else {
  142.       t1 *= t1;
  143.       n1 = t1 * t1 * gi1.dot2(x1, y1);
  144.     }
  145.     var t2 = 0.5 - x2*x2-y2*y2;
  146.     if(t2<0) {
  147.       n2 = 0;
  148.     } else {
  149.       t2 *= t2;
  150.       n2 = t2 * t2 * gi2.dot2(x2, y2);
  151.     }
  152.     // Add contributions from each corner to get the final noise value.
  153.     // The result is scaled to return values in the interval [-1,1].
  154.     return 70 * (n0 + n1 + n2);
  155.   };
  156.  
  157.  
  158.  
  159. })(this);
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