Dispatch the Diamond-Square render pass onto a worker queue to keep the main thread free

Terrain2/Algorithms.swift

@@ -329,18 +329,24 @@ public class DiamondSquareGenerator: TerrainGenerator {
     }
 
     var algorithm: Algorithm
-    let texture: MTLTexture
+    let textures: [MTLTexture]
-    let textureSemaphore = DispatchSemaphore(value: 1)
+    private var activeTexture: Int = 0
 
     init?(device: MTLDevice) {
         let size = DiamondSquareGenerator.textureSize
-        let desc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat: .r32Float, width: size.width, height: size.height, mipmapped: false)
+        do {
-        desc.usage = [.shaderRead, .shaderWrite]
+            textures = try (0..<2).map { (i: Int) -> MTLTexture in
-        guard let tex = device.makeTexture(descriptor: desc) else {
+                let desc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat: .r32Float, width: size.width, height: size.height, mipmapped: false)
+                desc.usage = [.shaderRead, .shaderWrite]
+                guard let tex = device.makeTexture(descriptor: desc) else {
+                    throw KernelError.textureCreationFailed
+                }
+                return tex
+            }
+        } catch {
             print("Couldn't create texture for Diamond-Squares algorithm.")
             return nil
         }
-        texture = tex
 
         algorithm = Algorithm(grid: Box(origin: Point(), size: Size(w: DiamondSquareGenerator.textureSize.width, h: DiamondSquareGenerator.textureSize.height)))
     }
@@ -348,13 +354,15 @@ public class DiamondSquareGenerator: TerrainGenerator {
     func render() {
         let heightMap = algorithm.render()
         let region = MTLRegion(origin: MTLOrigin(), size: DiamondSquareGenerator.textureSize)
-        texture.replace(region: region, mipmapLevel: 0, withBytes: heightMap, bytesPerRow: MemoryLayout<Float>.stride * DiamondSquareGenerator.textureSize.width)
+        let newActiveTexture = (activeTexture + 1) % textures.count
+        textures[newActiveTexture].replace(region: region, mipmapLevel: 0, withBytes: heightMap, bytesPerRow: MemoryLayout<Float>.stride * DiamondSquareGenerator.textureSize.width)
+        activeTexture = newActiveTexture
     }
 
     // MARK: Algorithm
 
     var outTexture: MTLTexture {
-        return texture
+        return textures[activeTexture]
     }
 
     func encode(in encoder: MTLComputeCommandEncoder) {

Terrain2/Renderer.swift

@@ -34,14 +34,13 @@ class Renderer: NSObject, MTKViewDelegate {
     let inFlightSemaphore = DispatchSemaphore(value: maxBuffersInFlight)
     let regenerationSemaphore = DispatchSemaphore(value: 1)
 
+    let generatorQueue = DispatchQueue(label: "me.erynwells.Terrain.generatorQueue")
+
     var uniformBufferOffset = 0
-
     var uniformBufferIndex = 0
-
     var uniforms: UnsafeMutablePointer<Uniforms>
 
     var projectionMatrix: matrix_float4x4 = matrix_float4x4()
-
     var rotation: Float = 0
 
     var terrain: Terrain
@@ -142,7 +141,13 @@ class Renderer: NSObject, MTKViewDelegate {
 
     func scheduleAlgorithmIteration() {
         regenerationSemaphore.wait()
-        iterateTerrainAlgorithm = true
+        if !terrain.generator.needsGPU {
+            generatorQueue.async {
+                print("Rendering terrain...")
+                self.terrain.generator.render()
+                print("Rendering terrain...complete!")
+            }
+        }
         regenerationSemaphore.signal()
     }
 
@@ -161,9 +166,6 @@ class Renderer: NSObject, MTKViewDelegate {
         if iterateTerrainAlgorithm {
             if terrain.generator.needsGPU {
                 terrain.generator.updateUniforms()
-            } else {
-                print("Rendering terrain...")
-                terrain.generator.render()
             }
         }
 
@@ -198,7 +200,7 @@ class Renderer: NSObject, MTKViewDelegate {
             
             self.updateGameState()
 
-            if iterateTerrainAlgorithm && !terrain.generator.needsGPU, let computeEncoder = commandBuffer.makeComputeCommandEncoder() {
+            if iterateTerrainAlgorithm && terrain.generator.needsGPU, let computeEncoder = commandBuffer.makeComputeCommandEncoder() {
                 print("Scheduling terrain generator iteration with \(terrain.generator.name) algorithm")
                 computeEncoder.label = "Generator Encoder"
                 computeEncoder.pushDebugGroup("Generate Terrain: \(terrain.generator.name)")