implement parallel chunk mesh building

Sources/Voxelotl/CMakeLists.txt

@@ -54,6 +54,7 @@ add_executable(Voxelotl MACOSX_BUNDLE
   # Game logic classes
   Chunk.swift
   ChunkGeneration.swift
+  ChunkMeshGeneration.swift
   WorldGenerator.swift
   CubeMeshBuilder.swift
   ChunkMeshBuilder.swift

Sources/Voxelotl/ChunkMeshBuilder.swift

@@ -1,7 +1,5 @@
 struct ChunkMeshBuilder {
-  public static func build(world: World, chunkID: SIMD3<Int>) -> Mesh<VertexPositionNormalColorTexcoord, UInt16> {
+  public static func build(world: World, chunk: Chunk) -> Mesh<VertexPositionNormalColorTexcoord, UInt16> {
-    guard let chunk = world.getChunk(id: chunkID) else { return .empty }
-
     var vertices = [VertexPositionNormalColorTexcoord]()
     var indices = [UInt16]()
     chunk.forEach { block, position in

Sources/Voxelotl/ChunkMeshGeneration.swift

@@ -0,0 +1,47 @@
+import Foundation
+
+public struct ChunkMeshGeneration {
+  private let queue: OperationQueue
+  private let localReadyMeshes = ConcurrentDictionary<SIMD3<Int>, RendererMesh>()
+
+  weak var game: Game?
+  weak var renderer: Renderer?
+
+  init(queue: DispatchQueue) {
+    self.queue = OperationQueue()
+    self.queue.underlyingQueue = queue
+    self.queue.maxConcurrentOperationCount = 8
+    self.queue.qualityOfService = .userInitiated
+  }
+
+  public mutating func generate(chunkID: SIMD3<Int>, chunk: Chunk) {
+    self.queueGenerateJob(chunkID: chunkID, chunk: chunk)
+  }
+
+  func queueGenerateJob(chunkID: SIMD3<Int>, chunk: Chunk) {
+    self.queue.addOperation {
+      guard let game = self.game else {
+        return
+      }
+
+      guard let renderer = self.renderer else {
+        return
+      }
+
+      let mesh = ChunkMeshBuilder.build(world: game.world, chunk: chunk)
+      self.localReadyMeshes[chunkID] = renderer.createMesh(mesh)
+    }
+  }
+
+  public mutating func acceptReadyMeshes() {
+    guard let game = self.game else {
+      return
+    }
+
+    queue.waitUntilAllOperationsAreFinished()
+
+    for (chunkID, mesh) in self.localReadyMeshes.take() {
+      game.renderChunks.updateValue(mesh, forKey: chunkID)
+    }
+  }
+}

Sources/Voxelotl/Game.swift

@@ -27,6 +27,7 @@ class Game: GameDelegate {
   var world = World()
   var cubeMesh: RendererMesh?
   var renderChunks = [SIMD3<Int>: RendererMesh]()
+  var chunkMeshGeneration: ChunkMeshGeneration!
 
   func create(_ renderer: Renderer) {
     self.resetPlayer()
@@ -35,6 +36,9 @@ class Game: GameDelegate {
     self.cubeMesh = renderer.createMesh(CubeMeshBuilder.build(bound: .fromUnitCube(position: .zero, scale: .one)))
 
     renderer.clearColor = Color<Double>.black.mix(.white, 0.1).linear
+    self.chunkMeshGeneration = .init(queue: .global(qos: .userInitiated))
+    self.chunkMeshGeneration.game = self
+    self.chunkMeshGeneration.renderer = renderer
   }
 
   private func resetPlayer() {
@@ -110,13 +114,9 @@ class Game: GameDelegate {
 
     // Update chunk meshes if needed
     self.world.handleRenderDamagedChunks { id, chunk in
-      let mesh = ChunkMeshBuilder.build(world: self.world, chunkID: id)
+      self.chunkMeshGeneration.generate(chunkID: id, chunk: chunk)
-      if let renderMesh = renderer.createMesh(mesh) {
-        self.renderChunks[id] = renderMesh
-      } else {
-        self.renderChunks.removeValue(forKey: id)
-      }
     }
+    self.chunkMeshGeneration.acceptReadyMeshes()
 
     for (id, chunk) in self.renderChunks {
       let drawPos = SIMD3<Float>(id &<< Chunk.shift)