PerlinNoise.cpp

#include <PerlinNoise.hpp>
#include <cmath>
#include <random>
#include <algorithm>
#include <numeric>

// THIS IS A DIRECT TRANSLATION TO C++11 FROM THE REFERENCE
// JAVA IMPLEMENTATION OF THE IMPROVED PERLIN FUNCTION (see http://mrl.nyu.edu/~perlin/noise/)
// THE ORIGINAL JAVA IMPLEMENTATION IS COPYRIGHT 2002 KEN PERLIN

// I ADDED AN EXTRA METHOD THAT GENERATES A NEW PERMUTATION VECTOR (THIS IS NOT PRESENT IN THE ORIGINAL IMPLEMENTATION)

// Initialize with the reference values for the permutation vector
PerlinNoise::PerlinNoise() {

    // Initialize the permutation vector with the reference values
    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 };
    // Duplicate the permutation vector
    p.insert(p.end(), p.begin(), p.end());
}

// Generate a new permutation vector based on the value of seed
PerlinNoise::PerlinNoise(unsigned int seed) {
    p.resize(256);

    // Fill p with values from 0 to 255
    std::iota(p.begin(), p.end(), 0);

    // Initialize a random engine with seed
    std::default_random_engine engine(seed);

    // Suffle  using the above random engine
    std::shuffle(p.begin(), p.end(), engine);

    // Duplicate the permutation vector
    p.insert(p.end(), p.begin(), p.end());
}

double PerlinNoise::noise(double x, double y, double z) {
    // Find the unit cube that contains the 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;

    // Add blended results from 8 corners of cube
    double res = 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))));
    return (res + 1.0)/2.0;
}

double PerlinNoise::fade(double t) { 
    return t * t * t * (t * (t * 6 - 15) + 10);
}

double PerlinNoise::lerp(double t, double a, double b) { 
    return a + t * (b - a);
}

double PerlinNoise::grad(int hash, double x, double y, double z) {
    int h = hash & 15;
    // Convert lower 4 bits of hash into 12 gradient directions
    double 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);
}