noise.c

int p[512] = { 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
               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 };

double lerp(double t, double a, double b) 
{
    return a + t * (b - a); 
} 
       
double fade(double t) 
{
    return t * t * t * (t * (t * 6 - 15) + 10); 
}
       
double grad(int hash, double x, double y, double z) 
{
    int    h = hash & 15;  
    double u = h<8 ? x : y;
    double v = h<4 ? y : h==12||h==14 ? x : z;
    return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
}       

double noise1(double x)
{
    return noise3(x, 0.0, 0.0);
}
       
double noise2(double x, double y)
{
    return noise3(x, y, 0.0);
}
       
double noise3(double x, double y, double z) 
{
    int X = (int)floor(x) & 255;
    int Y = (int)floor(y) & 255;
    int Z = (int)floor(z) & 255;
    
    x -= floor(x);
    y -= floor(y);
    z -= floor(z);
    
    double u = fade(x);
    double v = fade(y);
    double w = fade(z);
    
    int A  = p[X  ]+Y;
    int AA = p[A]  +Z;
    int AB = p[A+1]+Z;
    int B  = p[X+1]+Y;
    int BA = p[B]  +Z;
    int BB = p[B+1]+Z;

    return lerp(w, lerp(v, lerp(u, grad(p[AA  ], x  , y  , z   ), 
                                   grad(p[BA  ], x-1, y  , z   )), 
                           lerp(u, grad(p[AB  ], x  , y-1, z   ),  
                                   grad(p[BB  ], x-1, y-1, z   ))),
                   lerp(v, lerp(u, grad(p[AA+1], x  , y  , z-1 ),  
                                   grad(p[BA+1], x-1, y  , z-1 )), 
                           lerp(u, grad(p[AB+1], x  , y-1, z-1 ),
                                   grad(p[BB+1], x-1, y-1, z-1 ))));
}