perlin.js

(function(global){
  var module = global.noise = {};

  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;
  };

  Grad.prototype.dot3 = function(x, y, z) {
    return this.x*x + this.y*y + this.z*z;
  };

  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,
  5,202,38,147,118,126,255,89,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
  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];
  // Dobra a tabela de permutação
  var perm = new Array(512);
  var gradP = new Array(512);

  // Função de seed
  module.seed = function(seed) {
    if(seed > 0 && seed < 1) {
      // Limita a seed a 2^16 (acredito que nao precise mais que isso)
      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];
    }
  };

  module.seed(0);

  // Constantes da fórmula Simplex
  var F3 = 1/3;
  var G3 = 1/6;

  module.simplex3 = function(xin, yin, zin) {
    var n0, n1, n2, n3; // Quatro pontos do tetraedo

    // Vasculha o espaço determinando em qual parte do simplex esta o cursor
    var s = (xin+yin+zin)*F3;
    var i = Math.floor(xin+s);
    var j = Math.floor(yin+s);
    var k = Math.floor(zin+s);

    // Distâncias x,y iniciais
    var t = (i+j+k)*G3;
    var x0 = xin-i+t;
    var y0 = yin-j+t;
    var z0 = zin-k+t;

    var i1, j1, k1; // Offset do segundo canto do simplex em coordenada x,i,z
    var i2, j2, k2; // Offset do terceiro canto do simplex em coordenada x,i,z

    // Coordenadas do tetraedo para a formula
    if(x0 >= y0) {
      if(y0 >= z0){ 
        i1=1; 
        j1=0; 
        k1=0; 
        i2=1; 
        j2=1; 
        k2=0; 
      }else if(x0 >= z0){ 
        i1=1; 
        j1=0; 
        k1=0; 
        i2=1; 
        j2=0; 
        k2=1; 
      }else{ 
        i1=0; 
        j1=0; 
        k1=1; 
        i2=1; 
        j2=0; 
        k2=1; 
      }
    }else{
      if(y0 < z0){ 
        i1=0; 
        j1=0; 
        k1=1; 
        i2=0; 
        j2=1; 
        k2=1; 
      }else if(x0 < z0){ 
        i1=0; 
        j1=1;
        k1=0; 
        i2=0; 
        j2=1; 
        k2=1; 
      }else{ 
        i1=0; 
        j1=1; 
        k1=0; 
        i2=1; 
        j2=1; 
        k2=0; 
      }
    }

    var x1 = x0 - i1 + G3; // Offset do segundo canto
    var y1 = y0 - j1 + G3;
    var z1 = z0 - k1 + G3;

    var x2 = x0 - i2 + 2 * G3; // Offset do terceiro canto
    var y2 = y0 - j2 + 2 * G3;
    var z2 = z0 - k2 + 2 * G3;

    var x3 = x0 - 1 + 3 * G3; // Offset do quarto ponto
    var y3 = y0 - 1 + 3 * G3;
    var z3 = z0 - 1 + 3 * G3;

    // Trabalha no hash dos indices do gradiente dos 4 cantos do simplex
    i &= 255;
    j &= 255;
    k &= 255;
    var gi0 = gradP[i+   perm[j+   perm[k   ]]];
    var gi1 = gradP[i+i1+perm[j+j1+perm[k+k1]]];
    var gi2 = gradP[i+i2+perm[j+j2+perm[k+k2]]];
    var gi3 = gradP[i+ 1+perm[j+ 1+perm[k+ 1]]];

    // Calcula a contribuição dos 4 Cantos
    var t0 = 0.6 - x0*x0 - y0*y0 - z0*z0;
    if(t0<0) {
      n0 = 0;
    } else {
      t0 *= t0;
      n0 = t0 * t0 * gi0.dot3(x0, y0, z0);
    }
    var t1 = 0.6 - x1*x1 - y1*y1 - z1*z1;
    if(t1<0) {
      n1 = 0;
    } else {
      t1 *= t1;
      n1 = t1 * t1 * gi1.dot3(x1, y1, z1);
    }
    var t2 = 0.6 - x2*x2 - y2*y2 - z2*z2;
    if(t2<0) {
      n2 = 0;
    } else {
      t2 *= t2;
      n2 = t2 * t2 * gi2.dot3(x2, y2, z2);
    }
    var t3 = 0.6 - x3*x3 - y3*y3 - z3*z3;
    if(t3<0) {
      n3 = 0;
    } else {
      t3 *= t3;
      n3 = t3 * t3 * gi3.dot3(x3, y3, z3);
    }
    
    // O retorno é calculado para que retorne valores entre -1 e 1
    return 32 * (n0 + n1 + n2 + n3);

  };
})(this);