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...

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)
     }
 }