From e9a09fff3e981ec373beec3bea2bdae221d4310c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nicolas=20Ma=CC=88rki?= <maerki@ubique.ch>
Date: Mon, 4 Nov 2024 20:29:50 +0100
Subject: [PATCH] use global buffer index
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Nicolas Märki <maerki@ubique.ch>
---
 ios/graphics/Model/MultiBuffer.swift | 22 +++----
 ios/graphics/RenderingContext.swift  | 91 +++++++++++++++++-----------
 2 files changed, 62 insertions(+), 51 deletions(-)

diff --git a/ios/graphics/Model/MultiBuffer.swift b/ios/graphics/Model/MultiBuffer.swift
index 007599241..e05239ce5 100644
--- a/ios/graphics/Model/MultiBuffer.swift
+++ b/ios/graphics/Model/MultiBuffer.swift
@@ -8,14 +8,10 @@
 import Metal
 import simd
 
-private let bufferCount = 3  // Triple buffering
-
 public struct MultiBuffer<DataType> {
     // Warning: Seems like suited to be generic
     // But makeBuffer &reference does not like generic data
     var buffers: [MTLBuffer]
-    var currentBufferIndex = 0
-    var currentFrameId = -1
 
     fileprivate init(buffers: [MTLBuffer]) {
         self.buffers = buffers
@@ -24,21 +20,15 @@ public struct MultiBuffer<DataType> {
     public mutating func getNextBuffer(_ context: RenderingContext)
         -> MTLBuffer?
     {
-        if context.frameId != currentFrameId {
-            currentBufferIndex = (currentBufferIndex + 1) % bufferCount
-            currentFrameId = context.frameId
-        }
-        guard currentBufferIndex < buffers.count else {
-            return nil
-        }
-        return buffers[currentBufferIndex]
+        return buffers[context.currentBufferIndex]
     }
 }
 
 extension MultiBuffer<simd_float1> {
     public init(device: MTLDevice) {
         var initialMutable = simd_float1(1.0)
-        let buffers: [MTLBuffer] = (0..<bufferCount).compactMap { _ in
+        let buffers: [MTLBuffer] = (0..<RenderingContext.bufferCount).compactMap
+        { _ in
             device
                 .makeBuffer(
                     bytes: &initialMutable,
@@ -52,7 +42,8 @@ extension MultiBuffer<simd_float1> {
 extension MultiBuffer<simd_float4> {
     public init(device: MTLDevice) {
         var initialMutable = simd_float4(0.0, 0.0, 0.0, 0.0)
-        let buffers: [MTLBuffer] = (0..<bufferCount).compactMap { _ in
+        let buffers: [MTLBuffer] = (0..<RenderingContext.bufferCount).compactMap
+        { _ in
             device
                 .makeBuffer(
                     bytes: &initialMutable,
@@ -66,7 +57,8 @@ extension MultiBuffer<simd_float4> {
 extension MultiBuffer<simd_float4x4> {
     public init(device: MTLDevice) {
         var initialMutable = simd_float4x4(1.0)
-        let buffers: [MTLBuffer] = (0..<bufferCount).compactMap { _ in
+        let buffers: [MTLBuffer] = (0..<RenderingContext.bufferCount).compactMap
+        { _ in
             device
                 .makeBuffer(
                     bytes: &initialMutable,
diff --git a/ios/graphics/RenderingContext.swift b/ios/graphics/RenderingContext.swift
index 67c015fd5..603c73463 100644
--- a/ios/graphics/RenderingContext.swift
+++ b/ios/graphics/RenderingContext.swift
@@ -18,10 +18,13 @@ public class RenderingContext: NSObject, @unchecked Sendable {
     public weak var encoder: MTLRenderCommandEncoder?
     public weak var computeEncoder: MTLComputeCommandEncoder?
     public weak var sceneView: MCMapView?
-    private(set) var frameId: Int = 0
+
+    public static let bufferCount = 3  // Triple buffering
+    private(set) var currentBufferIndex = 0
 
     public func beginFrame() {
-        frameId = (frameId + 1) % 1000
+        currentBufferIndex =
+            (currentBufferIndex + 1) % RenderingContext.bufferCount
     }
 
     public var cullMode: MCRenderingCullMode?
@@ -36,7 +39,8 @@ public class RenderingContext: NSObject, @unchecked Sendable {
         let depthStencilDescriptor = MTLDepthStencilDescriptor()
         depthStencilDescriptor.frontFaceStencil = descriptor
         depthStencilDescriptor.backFaceStencil = descriptor
-        return MetalContext.current.device.makeDepthStencilState(descriptor: depthStencilDescriptor)
+        return MetalContext.current.device.makeDepthStencilState(
+            descriptor: depthStencilDescriptor)
     }()
 
     public lazy var polygonMask: MTLDepthStencilState? = {
@@ -49,7 +53,8 @@ public class RenderingContext: NSObject, @unchecked Sendable {
         let depthStencilDescriptor = MTLDepthStencilDescriptor()
         depthStencilDescriptor.frontFaceStencil = descriptor
         depthStencilDescriptor.backFaceStencil = descriptor
-        return MetalContext.current.device.makeDepthStencilState(descriptor: depthStencilDescriptor)
+        return MetalContext.current.device.makeDepthStencilState(
+            descriptor: depthStencilDescriptor)
     }()
 
     public lazy var defaultMask: MTLDepthStencilState? = {
@@ -59,7 +64,8 @@ public class RenderingContext: NSObject, @unchecked Sendable {
         let depthStencilDescriptor = MTLDepthStencilDescriptor()
         depthStencilDescriptor.frontFaceStencil = descriptor
         depthStencilDescriptor.backFaceStencil = descriptor
-        return MetalContext.current.device.makeDepthStencilState(descriptor: depthStencilDescriptor)
+        return MetalContext.current.device.makeDepthStencilState(
+            descriptor: depthStencilDescriptor)
     }()
 
     public var aspectRatio: Float {
@@ -72,7 +78,9 @@ public class RenderingContext: NSObject, @unchecked Sendable {
 
     var currentPipeline: MTLRenderPipelineState?
 
-    open func setRenderPipelineStateIfNeeded(_ pipelineState: MTLRenderPipelineState) {
+    open func setRenderPipelineStateIfNeeded(
+        _ pipelineState: MTLRenderPipelineState
+    ) {
         guard currentPipeline?.hash != pipelineState.hash else {
             return
         }
@@ -83,26 +91,32 @@ public class RenderingContext: NSObject, @unchecked Sendable {
     /// a Quad that fills the whole viewport
     /// this is needed to clear the stencilbuffer
     lazy var stencilClearQuad: Quad2d = {
-        let quad = Quad2d(shader: ClearStencilShader(), metalContext: .current, label: "ClearStencil")
-        quad.setFrame(.init(topLeft: .init(x: 1, y: -1, z: 0),
-                            topRight: .init(x: -1, y: -1, z: 0),
-                            bottomRight: .init(x: -1, y: 1, z: 0),
-                            bottomLeft: .init(x: 1, y: 1, z: 0)),
-                      textureCoordinates: .init(x: 0, y: 0, width: 0, height: 0), origin: .init(x: 0, y: 0, z: 0), is3d: false)
+        let quad = Quad2d(
+            shader: ClearStencilShader(), metalContext: .current,
+            label: "ClearStencil")
+        quad.setFrame(
+            .init(
+                topLeft: .init(x: 1, y: -1, z: 0),
+                topRight: .init(x: -1, y: -1, z: 0),
+                bottomRight: .init(x: -1, y: 1, z: 0),
+                bottomLeft: .init(x: 1, y: 1, z: 0)),
+            textureCoordinates: .init(x: 0, y: 0, width: 0, height: 0),
+            origin: .init(x: 0, y: 0, z: 0), is3d: false)
         quad.setup(self)
         return quad
     }()
 
     public func clearStencilBuffer() {
         guard let encoder else { return }
-        stencilClearQuad.render(encoder: encoder,
-                                context: self,
-                                renderPass: .init(renderPass: 0, isPassMasked: false),
-                                vpMatrix: 0,
-                                mMatrix: 0,
-                                origin: .init(x: 0, y: 0, z: 0),
-                                isMasked: false,
-                                screenPixelAsRealMeterFactor: 1)
+        stencilClearQuad.render(
+            encoder: encoder,
+            context: self,
+            renderPass: .init(renderPass: 0, isPassMasked: false),
+            vpMatrix: 0,
+            mMatrix: 0,
+            origin: .init(x: 0, y: 0, z: 0),
+            isMasked: false,
+            screenPixelAsRealMeterFactor: 1)
     }
 }
 
@@ -110,7 +124,7 @@ extension RenderingContext: MCRenderingContextInterface {
     public func setCulling(_ mode: MCRenderingCullMode) {
         self.cullMode = mode
     }
-    
+
     public func preRenderStencilMask() {
     }
 
@@ -125,14 +139,14 @@ extension RenderingContext: MCRenderingContextInterface {
              Set the cullMode inverse in order to be consistent with opengl
              */
             switch cullMode {
-                case .BACK:
-                    encoder?.setCullMode(.front)
-                case .FRONT:
-                    encoder?.setCullMode(.back)
-                case .NONE:
-                    encoder?.setCullMode(.none)
-                @unknown default:
-                    assertionFailure()
+            case .BACK:
+                encoder?.setCullMode(.front)
+            case .FRONT:
+                encoder?.setCullMode(.back)
+            case .NONE:
+                encoder?.setCullMode(.none)
+            @unknown default:
+                assertionFailure()
             }
         }
     }
@@ -160,13 +174,17 @@ extension RenderingContext: MCRenderingContextInterface {
             var s = CGSize(width: 1.0, height: 1.0)
             if Thread.isMainThread {
                 MainActor.assumeIsolated {
-                    s = self.sceneView?.frame.size ?? CGSize(width: 1.0, height: 1.0)
+                    s =
+                        self.sceneView?.frame.size
+                        ?? CGSize(width: 1.0, height: 1.0)
                     s.width = UIScreen.main.nativeScale * s.width
                     s.height = UIScreen.main.nativeScale * s.height
                 }
             } else {
                 DispatchQueue.main.sync {
-                    s = self.sceneView?.frame.size ?? CGSize(width: 1.0, height: 1.0)
+                    s =
+                        self.sceneView?.frame.size
+                        ?? CGSize(width: 1.0, height: 1.0)
                     s.width = UIScreen.main.nativeScale * s.width
                     s.height = UIScreen.main.nativeScale * s.height
                 }
@@ -182,14 +200,15 @@ extension RenderingContext: MCRenderingContextInterface {
     }
 }
 
-private extension MCRectI {
-    var scissorRect: MTLScissorRect {
-        MTLScissorRect(x: Int(x), y: Int(y), width: Int(width), height: Int(height))
+extension MCRectI {
+    fileprivate var scissorRect: MTLScissorRect {
+        MTLScissorRect(
+            x: Int(x), y: Int(y), width: Int(width), height: Int(height))
     }
 }
 
-private extension MCVec2I {
-    var scissorRect: MTLScissorRect {
+extension MCVec2I {
+    fileprivate var scissorRect: MTLScissorRect {
         MTLScissorRect(x: 0, y: 0, width: Int(x), height: Int(y))
     }
 }