Move shader files to Shaders group

Terrain2/Shaders/TerrainAlgorithms.metal

@@ -0,0 +1,62 @@
+//
+//  TerrainAlgorithms.metal
+//  Terrain2
+//
+//  Created by Eryn Wells on 11/4/18.
+//  Copyright © 2018 Eryn Wells. All rights reserved.
+//
+
+#include <metal_stdlib>
+#include <metal_types>
+#include "ShaderTypes.h"
+using namespace metal;
+
+/// 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;
+};
+
+kernel void zeroKernel(texture2d<float, access::write> outTexture [[texture(GeneratorTextureIndexOut)]],
+                       uint2 tid [[thread_position_in_grid]])
+{
+    outTexture.write(0, tid);
+}
+
+#pragma mark - RandomAlgorithm
+
+kernel void randomKernel(texture2d<float, access::write> outTexture [[texture(GeneratorTextureIndexOut)]],
+                         constant RandomAlgorithmUniforms &uniforms [[buffer(0)]],
+                         uint2 tid [[thread_position_in_grid]])
+{
+    PRNG rng(uniforms.randoms[(tid.x * tid.y) % kRandomAlgorithmUniforms_RandomCount]);
+    uint r = rng.xorShift();
+    float x = float(r * (1.0 / float(UINT_MAX))) * 0.5f;
+    outTexture.write(x, tid);
+}