text: // http://mrl.nyu.edu/~perlin/noise/
  
  var ImprovedNoise = function () {
  
  	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 ];
  
  	for (var i = 0; i < 256 ; i ++) {
  
  		p[256 + i] = p[i];
  
  	}
  
  	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) {
  
  		var h = hash & 15;
  		var 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);
  
  	}
  
  	return {
  
  		noise: function (x, y, z) {
  
  			var floorX = ~~x, floorY = ~~y, floorZ = ~~z;
  
  			var X = floorX & 255, Y = floorY & 255, Z = floorZ & 255;
  
  			x -= floorX;
  			y -= floorY;
  			z -= floorZ;
  
  			var xMinus1 = x - 1, yMinus1 = y - 1, zMinus1 = z - 1;
  
  			var u = fade(x), v = fade(y), w = fade(z);
  
  			var 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], xMinus1, y, z)),
  						lerp(u, grad(p[AB], x, yMinus1, z),
  							grad(p[BB], xMinus1, yMinus1, z))),
  					lerp(v, lerp(u, grad(p[AA + 1], x, y, zMinus1),
  							grad(p[BA + 1], xMinus1, y, z - 1)),
  						lerp(u, grad(p[AB + 1], x, yMinus1, zMinus1),
  							grad(p[BB + 1], xMinus1, yMinus1, zMinus1))));
  
  		}
  	}
  };
  