Move PRNG to Random.hh

Terrain2/Shaders/Random.hh

@@ -0,0 +1,44 @@
+//
+//  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 */