Add a Uniform object for RandomAlgorithm

This object contains several random numbers for the GPU kernel to use when generating random points. This isn't right yet (there are still patterns in the generated data) but it's time to move on...

Terrain.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		C019C8512191CE7100EAD5BB /* Uniforms.m in Sources */ = {isa = PBXBuildFile; fileRef = C019C8502191CE7100EAD5BB /* Uniforms.m */; };
 		C08C58A0218F46F000EAFC2D /* Algorithms.swift in Sources */ = {isa = PBXBuildFile; fileRef = C08C589F218F46F000EAFC2D /* Algorithms.swift */; };
 		C08C58A2218F474E00EAFC2D /* TerrainAlgorithms.metal in Sources */ = {isa = PBXBuildFile; fileRef = C08C58A1218F474E00EAFC2D /* TerrainAlgorithms.metal */; };
 		C0C15A8E218DDD85007494E2 /* AppDelegate.swift in Sources */ = {isa = PBXBuildFile; fileRef = C0C15A8D218DDD85007494E2 /* AppDelegate.swift */; };
@@ -29,6 +30,7 @@
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
+		C019C8502191CE7100EAD5BB /* Uniforms.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = Uniforms.m; sourceTree = "<group>"; };
 		C08C589F218F46F000EAFC2D /* Algorithms.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = Algorithms.swift; sourceTree = "<group>"; };
 		C08C58A1218F474E00EAFC2D /* TerrainAlgorithms.metal */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.metal; path = TerrainAlgorithms.metal; sourceTree = "<group>"; };
 		C0C15A8A218DDD85007494E2 /* Terrain.app */ = {isa = PBXFileReference; explicitFileType = wrapper.application; includeInIndex = 0; path = Terrain.app; sourceTree = BUILT_PRODUCTS_DIR; };
@@ -133,6 +135,7 @@
 				C0C15AB8218E2A90007494E2 /* Shaders.metal */,
 				C08C58A1218F474E00EAFC2D /* TerrainAlgorithms.metal */,
 				C0C15ABA218E2A90007494E2 /* ShaderTypes.h */,
+				C019C8502191CE7100EAD5BB /* Uniforms.m */,
 				C0C15ABB218E2A90007494E2 /* Assets.xcassets */,
 				C0C15ABD218E2A90007494E2 /* Main.storyboard */,
 				C0C15AC0218E2A90007494E2 /* Info.plist */,
@@ -260,6 +263,7 @@
 				C0C15AC6218E32B3007494E2 /* Terrain.swift in Sources */,
 				C0C15AB7218E2A90007494E2 /* Renderer.swift in Sources */,
 				C0C15AB3218E2A90007494E2 /* AppDelegate.swift in Sources */,
+				C019C8512191CE7100EAD5BB /* Uniforms.m in Sources */,
 				C08C58A0218F46F000EAFC2D /* Algorithms.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

Terrain2/Algorithms.swift

@@ -18,6 +18,7 @@ protocol Algorithm {
     var name: String { get }
     var outTexture: MTLTexture { get }
 
+    func updateUniforms()
     func encode(in encoder: MTLComputeCommandEncoder)
 }
 
@@ -33,6 +34,7 @@ class Kernel {
 
     let pipeline: MTLComputePipelineState
     let textures: [MTLTexture]
+    let uniformBuffer: MTLBuffer?
 
     var outTexture: MTLTexture {
         return textures[textureIndexes.out]
@@ -40,7 +42,7 @@ class Kernel {
 
     private(set) var textureIndexes: (`in`: Int, out: Int) = (in: 0, out: 1)
 
-    init(device: MTLDevice, library: MTLLibrary, functionName: String) throws {
+    init(device: MTLDevice, library: MTLLibrary, functionName: String, uniformBuffer: MTLBuffer? = nil) throws {
         guard let computeFunction = library.makeFunction(name: functionName) else {
             throw KernelError.badFunction
         }
@@ -56,12 +58,15 @@ class Kernel {
             textures.append(tex)
         }
         self.textures = textures
+
+        self.uniformBuffer = uniformBuffer
     }
 
     func encode(in encoder: MTLComputeCommandEncoder) {
         encoder.setComputePipelineState(pipeline)
         encoder.setTexture(textures[textureIndexes.in], index: textureIndexes.in)
         encoder.setTexture(textures[textureIndexes.out], index: textureIndexes.out)
+        encoder.setBuffer(uniformBuffer, offset: 0, index: 0)
         encoder.dispatchThreads(Kernel.textureSize, threadsPerThreadgroup: MTLSize(width: 8, height: 8, depth: 1))
     }
 }
@@ -78,19 +83,39 @@ class ZeroAlgorithm: Kernel, Algorithm {
             return nil
         }
     }
+
+    // MARK: Algorithm
+
+    func updateUniforms() { }
 }
 
 /// Randomly generate heights that are independent of all others.
 class RandomAlgorithm: Kernel, Algorithm {
     let name = "Random"
 
+    private var uniforms: UnsafeMutablePointer<RandomAlgorithmUniforms>
+
     init?(device: MTLDevice, library: MTLLibrary) {
+        let bufferSize = (MemoryLayout<RandomAlgorithmUniforms>.stride & ~0xFF) + 0x100;
+        guard let buffer = device.makeBuffer(length: bufferSize, options: [.storageModeShared]) else {
+            print("Couldn't create uniform buffer")
+            return nil
+        }
+
+        uniforms = UnsafeMutableRawPointer(buffer.contents()).bindMemory(to: RandomAlgorithmUniforms.self, capacity:1)
+
         do {
-            try super.init(device: device, library: library, functionName: "randomKernel")
+            try super.init(device: device, library: library, functionName: "randomKernel", uniformBuffer: buffer)
         } catch let e {
             print("Couldn't create compute kernel. Error: \(e)")
             return nil
         }
+
+        updateUniforms()
+    }
+
+    func updateUniforms() {
+        RandomAlgorithmUniforms_refreshRandoms(uniforms)
     }
 }
 

Terrain2/Renderer.swift

@@ -151,6 +151,9 @@ class Renderer: NSObject, MTKViewDelegate {
 
     private func updateGameState() {
         /// Update any game state before rendering
+        if iterateTerrainAlgorithm {
+            terrain.algorithm.updateUniforms()
+        }
 
         uniforms[0].projectionMatrix = projectionMatrix
 

Terrain2/ShaderTypes.h

@@ -53,5 +53,15 @@ typedef struct
     matrix_float4x4 modelViewMatrix;
 } Uniforms;
 
+#define kRandomAlgorithmUniforms_RandomCount (41)
+
+typedef struct {
+    uint randoms[kRandomAlgorithmUniforms_RandomCount];
+} RandomAlgorithmUniforms;
+
+#ifndef __METAL_VERSION__
+extern void RandomAlgorithmUniforms_refreshRandoms(RandomAlgorithmUniforms *uniforms);
+#endif
+
 #endif /* ShaderTypes_h */
 

Terrain2/TerrainAlgorithms.metal

@@ -49,12 +49,14 @@ kernel void zeroKernel(texture2d<float, access::write> outTexture [[texture(Gene
     outTexture.write(0, tid);
 }
 
+#pragma mark - RandomAlgorithm
+
 kernel void randomKernel(texture2d<float, access::write> outTexture [[texture(GeneratorTextureIndexOut)]],
-                         uint2 tid [[thread_position_in_grid]],
-                         uint2 tgid [[threadgroup_position_in_grid]])
+                         constant RandomAlgorithmUniforms &uniforms [[buffer(0)]],
+                         uint2 tid [[thread_position_in_grid]])
 {
-    PRNG rng(tid.x * tid.y);
-    uint r = rng.lcg();
+    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);
 }

Terrain2/Uniforms.m

@@ -0,0 +1,16 @@
+//
+//  Uniforms.c
+//  Terrain2
+//
+//  Created by Eryn Wells on 11/6/18.
+//  Copyright © 2018 Eryn Wells. All rights reserved.
+//
+
+#include <stdio.h>
+#include "ShaderTypes.h"
+
+void RandomAlgorithmUniforms_refreshRandoms(RandomAlgorithmUniforms *uniforms) {
+    for (int i = 0; i < kRandomAlgorithmUniforms_RandomCount; i++) {
+        uniforms->randoms[i] = arc4random();
+    }
+}