PerlinNoise3D.h

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#ifndef PERLINNOISE_H
#define PERLINNOISE_H PERLINNOISE_H

#include "StdDefs.h"

class PerlinNoise3D {
    public:
        double noise (double x, double y, double z);

    private:
        double fade (double t) { return t*t*t*(t*(t*6-15)+10); }
        double lerp (double t, double a, double b) { return a + t * (b-a); }
        double grad (int hash, double x, double y, double z) {
            // convert lo 4 bits of hash code into 12 gradient directions
            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);
        }
        int p[512];
    public:
        PerlinNoise3D () {
            int permutation[] = { 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 (int i = 0; i < 256; i++)
                p[256+i] = p[i] = permutation [i];
        }
};

double PerlinNoise3D::noise (double x, double y, double z) {
    // find unit cube that contains point
    int X = (int)floor(x) & 255;
    int Y = (int)floor(y) & 255;
    int Z = (int)floor(z) & 255;
    // find relative x,y,z of point in cube
    x -= floor(x);
    y -= floor(y);
    z -= floor(z);
    // compute fade curves for each of x,y,z
    double u = fade(x);
    double v = fade(y);
    double w = fade(z);
    // hash coordinates of the 8 cube corners
    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;
    // and add blended results from 8 corners of cube
    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))));
}

#endif

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