44 lines
1 KiB
C++
44 lines
1 KiB
C++
//
|
|
// Random.hh
|
|
// Terrain
|
|
//
|
|
// Created by Eryn Wells on 11/22/18.
|
|
// Copyright © 2018 Eryn Wells. All rights reserved.
|
|
//
|
|
|
|
#ifndef Random_hh
|
|
#define Random_hh
|
|
|
|
/// A pseudo-random number generator providing several algorithms.
|
|
/// - http://reedbeta.com/blog/quick-and-easy-gpu-random-numbers-in-d3d11/
|
|
struct PRNG {
|
|
PRNG(uint seed) : mSeed(wangHash(seed)) { }
|
|
|
|
/// Generate a random unsigned integer using a linear congruential generator.
|
|
uint lcg() {
|
|
mSeed = 1664525 * mSeed + 1013904223;
|
|
return mSeed;
|
|
}
|
|
|
|
/// Generate a random unsigned integer using the Xorshift algorithm from George Marsaglia's paper.
|
|
uint xorShift() {
|
|
mSeed ^= (mSeed << 13);
|
|
mSeed ^= (mSeed >> 17);
|
|
mSeed ^= (mSeed << 5);
|
|
return mSeed;
|
|
}
|
|
|
|
uint wangHash(uint seed) {
|
|
seed = (seed ^ 61) ^ (seed >> 16);
|
|
seed *= 9;
|
|
seed = seed ^ (seed >> 4);
|
|
seed *= 0x27d4eb2d;
|
|
seed = seed ^ (seed >> 15);
|
|
return seed;
|
|
}
|
|
|
|
private:
|
|
uint mSeed;
|
|
};
|
|
|
|
#endif /* Random_hh */
|