three.js/examples/js/ImprovedNoise.js

// 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 ) ) ) );

		}
	}

};