Hey, I've been struggling with this for some days now. I am trying to write to a sparse texture in a compute shader. I'm performing the following steps: Set up a sparse heap and create a texture from it Map the whole area of the sparse texture using updateTextureMapping(..) Overwrite every value with the value "4" in a compute shader Blit the texture to a shared buffer Assert that the values in the buffer are "4". I have a minimal example (which is still pretty long unfortunately). It works perfectly when removing the line heapDesc.type = .sparse. What am I missing? I could not find any information that writes to sparse textures are unsupported. Any help would be greatly appreciated. import Metal func sparseTexture64x64Demo() throws { // ── Metal objects guard let device = MTLCreateSystemDefaultDevice() else { throw NSError(domain: "SparseNotSupported", code: -1) } let queue = device.makeCommandQueue()! let lib = device.makeDefaultLibrary()! let pipeline = try device.makeComputePipelineState(function: lib.makeFunction(name: "addOne")!) // ── Texture descriptor let width = 64, height = 64 let format: MTLPixelFormat = .r32Uint // 4 B per texel let desc = MTLTextureDescriptor() desc.textureType = .type2D desc.pixelFormat = format desc.width = width desc.height = height desc.storageMode = .private desc.usage = [.shaderWrite, .shaderRead] // ── Sparse heap let bytesPerTile = device.sparseTileSizeInBytes let meta = device.heapTextureSizeAndAlign(descriptor: desc) let heapBytes = ((bytesPerTile + meta.size + bytesPerTile - 1) / bytesPerTile) * bytesPerTile let heapDesc = MTLHeapDescriptor() heapDesc.type = .sparse heapDesc.storageMode = .private heapDesc.size = heapBytes let heap = device.makeHeap(descriptor: heapDesc)! let tex = heap.makeTexture(descriptor: desc)! // ── CPU buffers let bytesPerPixel = MemoryLayout<UInt32>.stride let rowStride = width * bytesPerPixel let totalBytes = rowStride * height let dstBuf = device.makeBuffer(length: totalBytes, options: .storageModeShared)! let cb = queue.makeCommandBuffer()! let fence = device.makeFence()! // 2. Map the sparse tile, then signal the fence let rse = cb.makeResourceStateCommandEncoder()! rse.updateTextureMapping( tex, mode: .map, region: MTLRegionMake2D(0, 0, width, height), mipLevel: 0, slice: 0) rse.update(fence) // ← capture all work so far rse.endEncoding() let ce = cb.makeComputeCommandEncoder()! ce.waitForFence(fence) ce.setComputePipelineState(pipeline) ce.setTexture(tex, index: 0) let threadsPerTG = MTLSize(width: 8, height: 8, depth: 1) let tgCount = MTLSize(width: (width + 7) / 8, height: (height + 7) / 8, depth: 1) ce.dispatchThreadgroups(tgCount, threadsPerThreadgroup: threadsPerTG) ce.updateFence(fence) ce.endEncoding() // Blit texture into shared buffer let blit = cb.makeBlitCommandEncoder()! blit.waitForFence(fence) blit.copy( from: tex, sourceSlice: 0, sourceLevel: 0, sourceOrigin: MTLOrigin(x: 0, y: 0, z: 0), sourceSize: MTLSize(width: width, height: height, depth: 1), to: dstBuf, destinationOffset: 0, destinationBytesPerRow: rowStride, destinationBytesPerImage: totalBytes) blit.endEncoding() cb.commit() cb.waitUntilCompleted() assert(cb.error == nil, "GPU error: \(String(describing: cb.error))") // ── Verify a few texels let out = dstBuf.contents().bindMemory(to: UInt32.self, capacity: width * height) print("first three texels:", out[0], out[1], out[width]) // 0 1 64 assert(out[0] == 4 && out[1] == 4 && out[width] == 4) } Metal shader: #include <metal_stdlib> using namespace metal; kernel void addOne(texture2d<uint, access::write> tex [[texture(0)]], uint2 gid [[thread_position_in_grid]]) { tex.write(4, gid); }

I'm running into a persistent visual issue while deploying a floral corridor scene to Apple Vision Pro using Unity 6.0 with URP and Metal. The issue only appears on the Vision Pro device — everything looks fine in the Unity Editor. Issue Description When the frame rate drops to around 60–70 FPS, noticeable distortion artifacts appear around the edges of foliage models. It seems like the background meshes (behind the plants) get warped and leak through the edges of the foliage. Although this is most visible around the leaves, even solid objects like standard URP wall or box models show distorted edges when the issue occurs. All the foliage uses Opaque or Alpha Clipping materials. Things I've Tried Changing the foliage materials to Transparent mode —distortion around edges disappears, but using Transparent for a large number of foliage assets is not ideal for performance or sorting complexity. Reducing the number of foliage objects — with only a few plants in the scene and the frame rate staying around 100 FPS, the distortion disappears. However, this isn’t a practical solution for a full environment. Possible Cause? I came across this note in the Unity documentation: "Ensure depth-buffer for each pixel is non-zero - on visionOS, the depth buffer is used for reprojection. To ensure visual effects like skyboxes and shaders are displayed beautifully, ensure that some value is written to the depth for each pixel." Could this be related to the issue? Is it possible that Alpha Clipping with low pixel coverage leads to some pixels not writing to the depth buffer, which then causes problems during Vision Pro’s reprojection or foveated rendering? However, even when I disable Alpha Clipping entirely, the distortion issue still persists, so it may not be solely caused by clipping itself. Project Setup Unity 6.0 (URP) Depth Texture: Enable Using Metal as the graphics backend Running on real Vision Pro hardware (not simulator) Any advice on how to avoid these distortion issues on Vision Pro would be greatly appreciated. Thanks!

hi everyone, 我们发现了一个和Metal相关崩溃。应用中使用了Metal相关的接口，在进行性能测试时，打开了设置-开发者-显示HUD图形。运行应用后，正常展示HUD，但应用很快发生了崩溃，日志主要信息如下： Incident Identifier: 1F093635-2DB8-4B29-9DA5-488A6609277B CrashReporter Key: 233e54398e2a0266d95265cfb96c5a89eb3403fd Hardware Model: iPhone14,3 Process: waimai [16584] Path: /private/var/containers/Bundle/Application/CCCFC0AE-EFB8-4BD8-B674-ED089B776221/waimai.app/waimai Identifier: Version: 61488 (8.53.0) Code Type: ARM-64 Parent Process: ? [1] Date/Time: 2025-06-12 14:41:45.296 +0800 OS Version: iOS 18.0 (22A3354) Report Version: 104 Monitor Type: Mach Exception Exception Type: EXC_BAD_ACCESS (SIGBUS) Exception Codes: KERN_PROTECTION_FAILURE at 0x000000014fffae00 Crashed Thread: 57 Thread 57 Crashed: 0 libMTLHud.dylib esfm_GenerateTriangesForString + 408 1 libMTLHud.dylib esfm_GenerateTriangesForString + 92 2 libMTLHud.dylib Renderer::DrawText(char const*, int, unsigned int) + 204 3 libMTLHud.dylib Overlay::onPresent(id<CAMetalDrawable>) + 1656 4 libMTLHud.dylib CAMetalDrawable_present(void (*)(), objc_object*, objc_selector*) + 72 5 libMTLHud.dylib invocation function for block in void replaceMethod<void>(objc_class*, objc_selector*, void (*)(void (*)(), objc_object*, objc_selector*)) + 56 6 Metal __45-[_MTLCommandBuffer presentDrawable:options:]_block_invoke + 104 7 Metal MTLDispatchListApply + 52 8 Metal -[_MTLCommandBuffer didScheduleWithStartTime:endTime:error:] + 312 9 IOGPU IOGPUNotificationQueueDispatchAvailableCompletionNotifications + 136 10 IOGPU __IOGPUNotificationQueueSetDispatchQueue_block_invoke + 64 11 libdispatch.dylib _dispatch_client_callout4 + 20 12 libdispatch.dylib _dispatch_mach_msg_invoke + 464 13 libdispatch.dylib _dispatch_lane_serial_drain + 368 14 libdispatch.dylib _dispatch_mach_invoke + 456 15 libdispatch.dylib _dispatch_lane_serial_drain + 368 16 libdispatch.dylib _dispatch_lane_invoke + 432 17 libdispatch.dylib _dispatch_lane_serial_drain + 368 18 libdispatch.dylib _dispatch_lane_invoke + 380 19 libdispatch.dylib _dispatch_root_queue_drain_deferred_wlh + 288 20 libdispatch.dylib _dispatch_workloop_worker_thread + 540 21 libsystem_pthread.dylib _pthread_wqthread + 288 我们测试了几个不同的机型，只有iPhone 13 Pro Max会发生崩溃。 Q1：为什么会发生这个崩溃？ Q2：相同的逻辑，为什么仅在iPhone 13 Pro Max机型上出现崩溃？ 期待您的解答。

Hi there, I'm wondering if it's possible under iOS 28 developer beta to enable MetalFX scaling info with '{"MTL_HUD_ENABLED": "1" for my App. This information has been added to Mac, but looks to be absent on iPhone / iPad

Hello, I'm tracking down a bug where useResource doesn't seem to apply proper synchronization when a resource is produced by the render pass then consumed by the compute pass, but when I use MTLFence between the to signal and wait between the render/compute encoders, the artifact goes away. The resource is created with MTLHazardTrackingModeTracked and useResource is called on the compute encoder after the render pass. Metal API Validation doesn't report any warnings/errors. Am I misunderstanding the difference between the two APIs? I dug through the Metal documentation and it looks like useResource should handle synchronization given the resource has MTLHazardTrackingModeTracked but on the other hand, MTLFence should be used to ensure proper synchronization between command encoders. Can someone can clarify the difference between the two APIs and when to use them.

I have really enjoyed looking through the code and videos related to Metal 4. Currently, my interest is to update a ReSTIR Project and take advantage of more robust ways to refit acceleration Structures and more powerful ways to access resources. I am working in Swift and have encountered a couple of puzzles: What is the 'accepted' way to create a MTL4BufferRange to store indices and vertices? How do I properly rewrite Swift code to build and compact an Acceleration Structure? I do realize that this is all in Beta and will happily look through Code Samples this Fall. If other guidance is available earlier, that would be fabulous! Thank you

I am developing a macOS terminal app, running on an M4 Pro, and using Metal. I am not able use float8 or float16, both reporting Variable has incomplete type 'float16' (aka '__Reserved_Name__Do_not_use_float16'). Based on the system I should be able to use these. Either it is because it is also compiling to Intel, which they are not allowed, or something else. Either way I have not been able to figure out how to get past this. IIs there a compiler setting I need to set to make this work? if so which one and what setting do I need? I only want to run this on M processes, on the latest version of OS so not interested in Intel version or backward compatibility.

Hello, I am experiencing an issue with programmatically capturing a GPU trace using MTLCaptureManager. The .gputrace file that is generated appears to be corrupted, and I'm looking for guidance or a solution. Description of the Problem: I am using MTLCaptureManager.sharedCaptureManager to capture a Metal frame and save it to disk. The generated .gputrace file is consistently reported as 0 bytes in size by the file system. Crucially, when I compress this 0-byte .gputrace file into a .zip archive, the resulting archive contains the full, expected data. After unzipping, the file can be opened and viewed correctly in Xcode. However,When inspecting the file's contents using NSFileManager in Objective-C (treating it as a directory), the internal structure is different from a .gputrace file captured directly from Xcode's Metal Debugger. capture in xcode capture in file Finally,When capturing multiple frames programmatically, the first captured frame contains valid buffer data. However, for subsequent frames (starting from the second frame), the corresponding buffer contents are all zero-filled. Frame 1: All MTLBuffer data is correctly captured and populated. Frame 2 and onward: The same MTLBuffer objects are present in the trace, but their contents are entirely 0 (i.e., the data is not captured or is corrupted). In this case, the on-screen display is normal, but the captured frame is incorrect. The frame captured directly in Xcode is also correct. Only the frame captured to a file is abnormal.

I mean…I want to use defaults rather than launching apps via open with the saved environment variables. This is pretty easy on iOS and other platforms. So what about in macOS?

Now the examples of metal-cpp are target on desktop and using AppKit which is not supported on iOS. Is there any tips for developing with metal-cpp on mobile device?

I have a very simple Mac app with just a MTKView in it which shows a single color. I want to move the rendering code to C++. For this I created a C++ framework target which interoperates with the Swift code - main project target. I am trying to link metal-cpp library to the C++ framework target using these instructions. Approach described in this article works with simple C++ Mac console apps. But in my mixed Swift/C++ project Xcode cannot find Foundation/Foundation.hpp (and probably other headers) to include into the C++ header. I inserted metal-cpp folder into my project and added it to C++ target's header search paths, as written in the instructions.

We have a production Metal app with a complex multithreaded Metal pipeline. When everything is operating smoothly, it works great. Even when extremely overloaded, it does not crash for days at a time. This isn't good enough for our users. Unfortunately, when I have zero visibility into id, I have no way of knowing when metal is "done" with an id. When overloaded, stale metal render passes need to be 'aborted', which results in metal callbacks not being called. for example, these callbacks may not be called after an aborted pass: id<MTLCommandBuffer> m_cmdbuf; [m_cmdbuf addScheduledHandler:^(id <MTLCommandBuffer> cb) { cpr->scheduled = MachAbsoluteTime(); }]; [m_cmdbuf addCompletedHandler:^(id <MTLCommandBuffer> cb) { cpr->completed = MachAbsoluteTime(); }]; For the moment, our workaround is a system which waits a few seconds after we "think" a rendering pass should be done with all its (aborted) resources before releasing buffers. This is not ideal, to say the least. So, in summary, my question is, it would be nice to be able to 'query' an id to know when metal is done with it, so that we know that its safe to release it along with our own internal resources. Is there any such (undocumented) mechanism? I have exhaustively read all existing Metal documentation many times. An idea that I've been toying with... it would be nice to have something akin to Zombie detection running all the time for id only. In OpenGL, it was OK to use a released texture... you may display a bad frame, but not CRASH!. Is there any similar option for id?

How many 32-bit variables can I use concurrently in a single thread of a Metal compute kernel without worrying about the variables getting spilled into the device memory? Alternatively: how many 32-bit registers does a single thread have available for itself? Let's say that each thread of my compute kernel needs to store and work with its own array of N float variables, where N can be 128, 256, 512 or more. To achieve maximum possible performance, I do not want to the local thread variables to get spilled into the slow device memory. I want all N variables to be stored "on-chip", in the thread memory space. To make my question more concrete, let's say there is an array thread float localArray[N]. Assuming an unrealistic hypothetical scenario where localArray is the only variable in the whole kernel, what is the maximum value of N for which no portion of localArray would get spilled into the device memory? I searched in the Metal feature set tables, but I could not find any details.

I'm trying to create a custom Metal-based visual effect as a UIView to be used inside an existing UIKit-based interface. (An example might be a view that applies a blur effect to what's behind it.) I need to capture the MTLTexture of what's behind the view so that I can feed it to MTLRenderCommandEncoder.setFragmentTexture(_:index:). Can someone show me how or point me to an example? Thanks!

Guten Tag, my project is simple, first I want draw wired Hexa,-Tetra- and Octahedrons. I draw a cube with Metal but I didn't found rotation, translation and scale. I have searched help , the examples I found are too complicated for me. Mit freundlichen Grüßen VanceRegnet

In my project I need to do the following: In runtime create metal Dynamic library from source. In runtime create metal Executable library from source and Link it with my previous created Dynamic library. Create compute pipeline using those two libraries created above. But I get the following error at the third step: Error Domain=AGXMetalG15X_M1 Code=2 "Undefined symbols: _Z5noisev, referenced from: OnTheFlyKernel " UserInfo={NSLocalizedDescription=Undefined symbols: _Z5noisev, referenced from: OnTheFlyKernel } import Foundation import Metal class MetalShaderCompiler { let device = MTLCreateSystemDefaultDevice()! var pipeline: MTLComputePipelineState! func compileDylib() -> MTLDynamicLibrary { let source = """ #include <metal_stdlib> using namespace metal; half3 noise() { return half3(1, 0, 1); } """ let option = MTLCompileOptions() option.libraryType = .dynamic option.installName = "@executable_path/libFoundation.metallib" let library = try! device.makeLibrary(source: source, options: option) let dylib = try! device.makeDynamicLibrary(library: library) return dylib } func compileExlib(dylib: MTLDynamicLibrary) -> MTLLibrary { let source = """ #include <metal_stdlib> using namespace metal; extern half3 noise(); kernel void OnTheFlyKernel(texture2d<half, access::read> src [[texture(0)]], texture2d<half, access::write> dst [[texture(1)]], ushort2 gid [[thread_position_in_grid]]) { half4 rgba = src.read(gid); rgba.rgb += noise(); dst.write(rgba, gid); } """ let option = MTLCompileOptions() option.libraryType = .executable option.libraries = [dylib] let library = try! self.device.makeLibrary(source: source, options: option) return library } func runtime() { let dylib = self.compileDylib() let exlib = self.compileExlib(dylib: dylib) let pipelineDescriptor = MTLComputePipelineDescriptor() pipelineDescriptor.computeFunction = exlib.makeFunction(name: "OnTheFlyKernel") pipelineDescriptor.preloadedLibraries = [dylib] pipeline = try! device.makeComputePipelineState(descriptor: pipelineDescriptor, options: .bindingInfo, reflection: nil) } }

There is a sample project from Apple here. It has a scene of a city at night and you can move in it. It basically has 2 parts: application code written in what looks like Objective-C (I am more familiar with C++), which inherits from things like NSObject, MTKView, NSViewController and so on - it processes input and all app-related and window-related stuff. rendering code that also looks like Objective-C. Btw both parts are mostly in .mm files (Obj-C++ AFAIK). The application part directly uses only one class from the rendering part - AAPLRenderer. I want to move the rendering part to C++ using metal-cpp. For that I need to link metal-cpp to the project. I did it successfully with blank projects several times before using this tutorial. But with this sample project Xcode can't find Foundation/Foundation.hpp (and other metal-cpp headers). The error says this: Did not find header 'Foundation.hpp' in framework 'Foundation' (loaded from '/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX15.0.sdk/System/Library/Frameworks') Pls help

Hello Everyone, within the renderEncoder?.drawIndexedPrimitives(type: .line…. function, I can't render all the lines of the object. I can see approx. 80%. Do you know what could be causing this? Other game engines, like those in C++, handle this just fine. import MetalKit class Renderer: NSObject, MTKViewDelegate { var parent: ContentView var metalDevice: MTLDevice! var metalCommandQueue: MTLCommandQueue! let allocator: MTKMeshBufferAllocator let pipelineState: MTLRenderPipelineState var scene: RenderScene let mesh: ObjMesh init(_ parent: ContentView) { self.parent = parent if let metalDevice = MTLCreateSystemDefaultDevice() { self.metalDevice = metalDevice } self.metalCommandQueue = metalDevice.makeCommandQueue() self.allocator = MTKMeshBufferAllocator(device: metalDevice) mesh = ObjMesh(device: metalDevice, allocator: allocator, filename: "cube") let pipelineDescriptor = MTLRenderPipelineDescriptor() let library = metalDevice.makeDefaultLibrary() pipelineDescriptor.vertexFunction = library?.makeFunction(name: "vertexShader") pipelineDescriptor.fragmentFunction = library?.makeFunction(name: "fragmentShader") pipelineDescriptor.colorAttachments[0].pixelFormat = .bgra8Unorm pipelineDescriptor.vertexDescriptor = MTKMetalVertexDescriptorFromModelIO(mesh.metalMesh.vertexDescriptor) do { try pipelineState = metalDevice.makeRenderPipelineState(descriptor: pipelineDescriptor) } catch { fatalError() } scene = RenderScene() super.init() } func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) { } func draw(in view: MTKView) { //update scene.update() guard let drawable = view.currentDrawable else { return } let commandBuffer = metalCommandQueue.makeCommandBuffer() let renderPassDescriptor = view.currentRenderPassDescriptor renderPassDescriptor?.colorAttachments[0].clearColor = MTLClearColorMake(0, 0.5, 0.5, 1.0) renderPassDescriptor?.colorAttachments[0].loadAction = .clear renderPassDescriptor?.colorAttachments[0].storeAction = .store let renderEncoder = commandBuffer?.makeRenderCommandEncoder(descriptor: renderPassDescriptor!) renderEncoder?.setRenderPipelineState(pipelineState) var cameraData: CameraParameters = CameraParameters() cameraData.view = Matrix44.create_lookat( eye: scene.player.position, target: scene.player.position + scene.player.forwards, up: scene.player.up ) cameraData.projection = Matrix44.create_perspective_projection( fovy: 45, aspect: 800/600, near: 0.1, far: 10 ) renderEncoder?.setVertexBytes(&cameraData, length: MemoryLayout<CameraParameters>.stride, index: 2) renderEncoder?.setVertexBuffer(mesh.metalMesh.vertexBuffers[0].buffer, offset: 0, index: 0) for cube in scene.cubes { var model: matrix_float4x4 = Matrix44.create_from_rotation(eulers: cube.eulers) model = Matrix44.create_from_translation(translation: cube.position) * model renderEncoder?.setVertexBytes(&model, length: MemoryLayout<matrix_float4x4>.stride, index: 1) for submesh in mesh.metalMesh.submeshes { renderEncoder?.drawIndexedPrimitives( type: .line, indexCount: submesh.indexCount, indexType: submesh.indexType, indexBuffer: submesh.indexBuffer.buffer, indexBufferOffset: submesh.indexBuffer.offset ) } } renderEncoder?.endEncoding() commandBuffer?.present(drawable) commandBuffer?.commit() } } ==================== import MetalKit class ObjMesh { let modelIOMesh: MDLMesh let metalMesh: MTKMesh init(device: MTLDevice, allocator: MTKMeshBufferAllocator, filename: String) { guard let meshURL = Bundle.main.url(forResource: filename, withExtension: "obj") else { fatalError() } let vertexDescriptor = MTLVertexDescriptor() var offset: Int = 0 //position vertexDescriptor.attributes[0].format = .float3 vertexDescriptor.attributes[0].offset = offset vertexDescriptor.attributes[0].bufferIndex = 0 offset += MemoryLayout<SIMD3<Float>>.stride vertexDescriptor.layouts[0].stride = offset let meshDescriptor = MTKModelIOVertexDescriptorFromMetal(vertexDescriptor) (meshDescriptor.attributes[0] as! MDLVertexAttribute).name = MDLVertexAttributePosition let asset = MDLAsset(url: meshURL, vertexDescriptor: meshDescriptor, bufferAllocator: allocator) self.modelIOMesh = asset.childObjects(of: MDLMesh.self).first as! MDLMesh do { metalMesh = try MTKMesh(mesh: self.modelIOMesh, device: device) } catch { fatalError("couldn't load mesh") } } } =============== cube.obj Blender v2.91.0 OBJ File: '' www_blender_org mtllib piece.mtl o Cube_Cube.001 v -1.000000 1.000000 -1.000000 v -1.000000 1.000000 1.000000 v 1.000000 1.000000 -1.000000 v 1.000000 1.000000 1.000000 v -1.000000 -1.000000 -1.000000 v -1.000000 -1.000000 1.000000 v 1.000000 -1.000000 -1.000000 v 1.000000 -1.000000 1.000000 vt 0.375000 0.000000 vt 0.625000 0.000000 vt 0.625000 0.250000 vt 0.375000 0.250000 vt 0.625000 0.500000 vt 0.375000 0.500000 vt 0.625000 0.750000 vt 0.375000 0.750000 vt 0.625000 1.000000 vt 0.375000 1.000000 vt 0.125000 0.500000 vt 0.125000 0.750000 vt 0.875000 0.500000 vt 0.875000 0.750000 vn 0.0000 1.0000 0.0000 vn 1.0000 0.0000 0.0000 vn 0.0000 -1.0000 0.0000 vn -1.0000 0.0000 0.0000 vn 0.0000 0.0000 -1.0000 vn 0.0000 0.0000 1.0000 usemtl None s off f 1/1/1 2/2/1 4/3/1 3/4/1 f 3/4/2 4/3/2 8/5/2 7/6/2 f 7/6/3 8/5/3 6/7/3 5/8/3 f 5/8/4 6/7/4 2/9/4 1/10/4 f 3/11/5 7/6/5 5/8/5 1/12/5 f 8/5/6 4/13/6 2/14/6 6/7/6

Given I do not understand much at all about how to write shaders I do not understand the math associated with page-curl effects I am trying to: implement a page-curl shader for use on SwiftUI views. I've lifted a shader from HIROKI IKEUCHI that I believe they lifted from a non-metal shader resource online, and I'm trying to digest it. One thing I want to do is to paint the "underside" of the view with a given color and maintain the transparency of rounded corners when they are flipped over. So, if an underside pixel is "clear" then I want to sample the pixel at that position on the original layer instead of the "curl effect" pixel. There are two comments in the shader below where I check the alpha, and underside flags, and paint the color red as a debug test. The shader gives this result: The outside of those rounded corners is appropriately red and the white border pixels are detected as "not-clear". But the "inner" portion of the border is... mistakingly red? I don't get it. Any help would be appreciated. I feel tapped out and I don't have any IRL resources I can ask. // // PageCurl.metal // ShaderDemo3 // // Created by HIROKI IKEUCHI on 2023/10/17. // #include <metal_stdlib> #include <SwiftUI/SwiftUI_Metal.h> using namespace metal; #define pi float(3.14159265359) #define blue half4(0.0, 0.0, 1.0, 1.0) #define red half4(1.0, 0.0, 0.0, 1.0) #define radius float(0.4) // そのピクセルの色を返す [[ stitchable ]] half4 pageCurl ( float2 _position, SwiftUI::Layer layer, float4 bounds, float2 _clickedPoint, float2 _mouseCursor ) { half4 undersideColor = half4(0.5, 0.5, 1.0, 1.0); float2 originalPosition = _position; // y座標の補正 float2 position = float2(_position.x, bounds.w - _position.y); float2 clickedPoint = float2(_clickedPoint.x, bounds.w - _clickedPoint.y); float2 mouseCursor = float2(_mouseCursor.x, bounds.w - _mouseCursor.y); float aspect = bounds.z / bounds.w; float2 uv = position * float2(aspect, 1.) / bounds.zw; float2 mouse = mouseCursor.xy * float2(aspect, 1.) / bounds.zw; float2 mouseDir = normalize(abs(clickedPoint.xy) - mouseCursor.xy); float2 origin = clamp(mouse - mouseDir * mouse.x / mouseDir.x, 0., 1.); float mouseDist = clamp(length(mouse - origin) + (aspect - (abs(clickedPoint.x) / bounds.z) * aspect) / mouseDir.x, 0., aspect / mouseDir.x); if (mouseDir.x < 0.) { mouseDist = distance(mouse, origin); } float proj = dot(uv - origin, mouseDir); float dist = proj - mouseDist; float2 linePoint = uv - dist * mouseDir; half4 pixel = layer.sample(position); if (dist > radius) { pixel = half4(0.0, 0.0, 0.0, 0.0); // background behind curling layer (note: 0.0 opacity) pixel.rgb *= pow(clamp(dist - radius, 0., 1.) * 1.5, .2); } else if (dist >= 0.0) { // THIS PORTION HANDLES THE CURL SHADED PORTION OF THE RESULT // map to cylinder point float theta = asin(dist / radius); float2 p2 = linePoint + mouseDir * (pi - theta) * radius; float2 p1 = linePoint + mouseDir * theta * radius; bool underside = (p2.x <= aspect && p2.y <= 1. && p2.x > 0. && p2.y > 0.); uv = underside ? p2 : p1; uv = float2(uv.x, 1.0 - uv.y); // invert y pixel = layer.sample(uv * float2(1. / aspect, 1.) * float2(bounds[2], bounds[3])); // ME<---- if (underside && pixel.a == 0.0) { //<---- PIXEL.A IS 0.0 WHYYYYY pixel = red; } // Commented out while debugging alpha issues // if (underside && pixel.a == 0.0) { // pixel = layer.sample(originalPosition); // } else if (underside) { // pixel = undersideColor; // underside // } // Shadow the pixel being returned pixel.rgb *= pow(clamp((radius - dist) / radius, 0., 1.), .2); } else { // THIS PORTION HANDLES THE NON-CURL-SHADED PORTION OF THE SAMPLING. float2 p = linePoint + mouseDir * (abs(dist) + pi * radius); bool underside = (p.x <= aspect && p.y <= 1. && p.x > 0. && p.y > 0.); uv = underside ? p : uv; uv = float2(uv.x, 1.0 - uv.y); // invert y pixel = layer.sample(uv * float2(1. / aspect, 1.) * float2(bounds[2], bounds[3])); // ME if (underside && pixel.a == 0.0) { //<---- PIXEL.A IS 0.0 WHYYYYY pixel = red; } // Commented out while debugging alpha issues // if (underside && pixel.a == 0.0) { // // If the new underside pixel is clear, we should sample the original image's pixel. // pixel = layer.sample(originalPosition); // } else if (underside) { // pixel = undersideColor; // } } return pixel; }

I am looking to implement CAMetalDisplayLink on a separate thread on a macOS application. I am basing my implementation on the following example project: Achieving Smooth Frame Rates with Metal Display Link This project allows you to configure whether a separate thread is used for rendering by setting RENDER_ON_MAIN_THREAD in GameConfig to 0. However, when I set it to use a separate thread nothing is rendered. Stepping through the code shows that a separate thread is created, but a CAMetalDisplayLinkUpdate is never received. Does anyone know why this does not work?