## Monday, 26 May 2014

### A Public Domain C++11 1D/2D/3D Perlin Noise Generator

Recently I needed to generate some simple procedural textures for a game I'm working on - after a quick search I found that the top result was licensed under the GPL which is no good to me. After a while I did find an MIT licensed one, but as all these code snippets are just C++ ports of Ken Perlin's improved noise function written in Java, I figured I might as well write my own from scratch and license it under the public domain. So, here it is, in all its glory:

```#ifndef NOISE_H
#define NOISE_H

#include <random>
#include <array>

namespace noise {

class Perlin {
public:
Perlin(uint32_t seed=0);

double noise(double x) const { return noise(x, 0, 0); }
double noise(double x, double y) const { return noise(x, y, 0); }
double noise(double x, double y, double z) const;

private:
std::array<int, 512> p;
};

class PerlinOctave {
public:
PerlinOctave(int octaves, uint32_t seed=0);

double noise(double x) const { return noise(x, 0, 0); }
double noise(double x, double y) const { return noise(x, y, 0); }
double noise(double x, double y, double z) const;

private:
Perlin perlin_;
int octaves_;
};

}

#endif // NOISE_H
```
And the source file...
```#include <algorithm>

#include "noise.h"

namespace noise {

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) {
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);
}

Perlin::Perlin(uint32_t seed) {
if(!seed) {
seed = time(0);
}

auto mid_range = p.begin() + 256;

std::mt19937 engine(seed);

std::iota(p.begin(), mid_range, 0); //Generate sequential numbers in the lower half
std::shuffle(p.begin(), mid_range, engine); //Shuffle the lower half
std::copy(p.begin(), mid_range, mid_range); //Copy the lower half to the upper half
//p now has the numbers 0-255, shuffled, and duplicated
}

double Perlin::noise(double x, double y, double z) const {
//See here for algorithm: http://cs.nyu.edu/~perlin/noise/

const int32_t X = static_cast<int32_t>(std::floor(x)) & 255;
const int32_t Y = static_cast<int32_t>(std::floor(y)) & 255;
const int32_t Z = static_cast<int32_t>(std::floor(z)) & 255;

x -= std::floor(x);
y -= std::floor(y);
z -= std::floor(z);

const auto A = p[X] + Y;
const auto AA = p[A] + Z;
const auto AB = p[A + 1] + Z;
const auto B = p[X + 1] + Y;
const auto BA = p[B] + Z;
const auto BB = p[B + 1] + Z;

const auto PAA = p[AA];
const auto PBA = p[BA];
const auto PAB = p[AB];
const auto PBB = p[BB];
const auto PAA1 = p[AA + 1];
const auto PBA1 = p[BA + 1];
const auto PAB1 = p[AB + 1];
const auto PBB1 = p[BB + 1];

const auto a = lerp(v,
);

const auto b = lerp(v,
);

return lerp(w, a, b);
}

PerlinOctave::PerlinOctave(int octaves, uint32_t seed):
perlin_(seed),
octaves_(octaves) {

}

double PerlinOctave::noise(double x, double y, double z) const {
double result = 0.0;
double amp = 1.0;

int i = octaves_;
while(i--) {
result += perlin_.noise(x, y, z) * amp;
x *= 2.0;
y *= 2.0;
z *= 2.0;
amp *= 0.5;
}

return result;
}

}
```

It's pretty straightforward to use, just instantiate a Perlin, or PerlinOctave instance, and call noise(x, y, z); Simples.

To clarify, I'm unlicensing this code. Use it however you want for whatever you want.

1. Thanks for this! For those stuck with older compilers that don't support C++11, you can just add #include to the header, and replace the Perlin constructor with the following:

template
void my_random_shuffle(RandomIt first, RandomIt last)
{
typename std::iterator_traits::difference_type i, n;
n = last - first;
for (i = n-1; i > 0; --i) {
int tmp = first[i];
int dst = std::rand() % (i+1);
first[i] = first[dst];
first[dst] = tmp;
}
}

template
void my_iota (ForwardIterator first, ForwardIterator last, T val)
{
while (first!=last) {
*first = val;
++first;
++val;
}
}

Perlin::Perlin(uint32_t seed) {

auto mid_range = p.begin() + 256;

my_iota(p.begin(), mid_range, 0); //Generate sequential numbers in the lower half
my_random_shuffle(p.begin(), mid_range); //Shuffle the lower half
std::copy(p.begin(), mid_range, mid_range); //Copy the lower half to the upper half
//p now has the numbers 0-255, shuffled, and duplicated
}

2. Thanks for this. I needed something simple I could integrate into my project without adding library dependencies or GPL code and this was really helpful.

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