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July 24, 2012 18:43
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Simplex Noise
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/* | |
* A speed-improved simplex noise algorithm for 2D, 3D and 4D in Java. | |
* | |
* Based on example code by Stefan Gustavson (stegu@itn.liu.se). | |
* Optimisations by Peter Eastman (peastman@drizzle.stanford.edu). | |
* Better rank ordering method by Stefan Gustavson in 2012. | |
* | |
* This could be speeded up even further, but it's useful as it is. | |
* | |
* Version 2012-03-09 | |
* | |
* This code was placed in the public domain by its original author, | |
* Stefan Gustavson. You may use it as you see fit, but | |
* attribution is appreciated. | |
* | |
* 2D version ported to Javascript by Arme138 | |
* original at: http://staffwww.itn.liu.se/~stegu/simplexnoise/SimplexNoise.java | |
*/ | |
// Inner class to speed upp gradient computations | |
// (array access is a lot slower than member access) | |
function Grad(x, y, z, w) | |
{ | |
this.x = x; | |
this.y = y; | |
this.z = z || 0; | |
this.w = w || 0; | |
} | |
var SimplexNoise = function() { | |
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, | |
5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42, | |
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]; | |
// To remove the need for index wrapping, double the permutation table length | |
var perm = []; | |
var permMod12 = []; | |
for(var i = 0; i < 512; i++) { | |
perm.push(p[i & 255]); | |
permMod12.push(perm[i] % 12); | |
} | |
// Skewing and unskewing factors for 2, 3, and 4 dimensions | |
var F2 = 0.5*(Math.sqrt(3.0)-1.0); | |
var G2 = (3.0-Math.sqrt(3.0))/6.0; | |
var F3 = 1.0/3.0; | |
var G3 = 1.0/6.0; | |
var F4 = (Math.sqrt(5.0)-1.0)/4.0; | |
var G4 = (5.0-Math.sqrt(5.0))/20.0; | |
// This method is a *lot* faster than using (int)Math.floor(x) | |
function fastfloor(x) { | |
return x | 0; | |
} | |
function dot(g, x, y, z, w) { | |
var optionalZ = z || 0, | |
optionalW = w || 0; | |
return g.x*x + g.y*y + g.z*optionalZ + g.w*optionalW; | |
} | |
this.noise2 = function(x, y) { | |
return Math.random() * 2.0 - 1.0; | |
}; | |
// 2D simplex noise | |
this.noise = function(xin, yin) { | |
var n0, n1, n2; // Noise contributions from the three corners | |
// Skew the input space to determine which simplex cell we're in | |
var s = (xin+yin)*F2; // Hairy factor for 2D | |
var i = fastfloor(xin+s); | |
var j = fastfloor(yin+s); | |
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 = permMod12[ii+perm[jj]]; | |
var gi1 = permMod12[ii+i1+perm[jj+j1]]; | |
var gi2 = permMod12[ii+1+perm[jj+1]]; | |
// 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 * dot(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 * dot(grad3[gi1], x1, y1); | |
} | |
var t2 = 0.5 - x2*x2-y2*y2; | |
if(t2<0) n2 = 0.0; | |
else { | |
t2 *= t2; | |
n2 = t2 * t2 * dot(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); | |
}; | |
} |
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