Hello! I have a question about how thread groups work with tile shading. When running "traditional" compute, I get to choose both thread group size and the grid size. However, when using tile shading kernel I only have dispatchThreadsPerTile method - this controls how many threads will be ran in each tile. So far so good, but what about thread groups? The examples in video "Tile Shading on A11" seem to suggest that there will be only one thread group per tile. In the video, [[thread_index_in_threadgroup]] is called "local_id" and it is used to access the image block. I assume this is the default configuration. So when one does the following: Creates MTLRenderPassDescriptor with tileWidth set to W and tileHeight set to H Fires up the tile shading kernel using dispatchThreadsPerTile with MTLSize size = { W, H, 1 } I understand that the result is 1-to-1 mapping between the tile "pixels" and kernel threads. Now, what I would like to do is to have more than one thread group there. I want this for performance reasons: I have a certain compute kernel which I know executes very well with small thread group size. In fact, { 32, 1, 1 } seems to be the fastest. My understanding is that even if I set tile size to 16x16, and so I am executing 256 threads there, there will only be one SIMD group active in a thread group. Meaning that this SIMD group has to execute 8 times over the tile. Is it possible somehow? Or perhaps the limitations of the API are pointing at the limitations of hardware itself, and if I want to execute with SIMD group sized thread groups I have to use "traditional" compute encoder? Will be grateful for help. Michał

Anyone else unable to download the "Rendering a Scene with Deferred Lighting in C++" (https://developer.apple.com/documentation/metal/rendering-a-scene-with-deferred-lighting-in-c++?language=objc)? I just an error page: Is there another place to download this sample?

Hello I am trying to get thread group memory access in fragment shader. In essence, I would like to have all the fragments in a tile to bitwiseOR some value. My idea was to use simd_or across the SIMD group, then make each SIMD group thread 0 to atomic or the value into thread group memory. Finally very first thread of the tile would be tasked with writing the value down to texture with write access. Now, I can allocate the thread group memory argument to the fragment function all right. MTLRenderEncoder has setThreadgroupMemoryLength call, which I am using the following way [renderEncoder setThreagroupMemoryLength: 16 offset: 0 atIndex:0] Unfortunately, all I am getting is the following error (runtime assertion) -[MTLDebugRenderCommandEncoder setThreadgroupMemoryLength:offset:atIndex:]:3487: failed assertion Set Threadgroup Memory Length Validation offset + length(16) must be <= threadgroupMemoryLength(0).` What I am doing wrong? How I can get thread group memory in the fragment shader? I know I could use tile shading and compute function but the problem is that here I really like to use fragment stuff. Will be grateful for help.

View Layout Add the following views in a view controller: Label View A, with a subview of the same size: MTKView A View B, with a subview of the same size: MTKView B Refresh Rates of Each View The label view refreshes at 60fps (driven by CADisplayLink). MTKView A and B refresh at 15fps. MTKView Implementation Details The corresponding CAMetalLayer's maximumDrawableCount is set to 2, changed to double buffering. The scheduling mechanism is modified; drawing is not driven by the internal loop but is done manually. The draw call is triggered immediately upon receiving a frame. self.metalView.enableSetNeedsDisplay = NO; self.metalView.paused = YES; A new high-priority queue is created for drawing, instead of handling it on the main queue. MTKView Latency Tracking The GPU completion time T1 is observed through the addCompletedHandler callback of the CommandBuffer. The presentation time T2 of the frame is observed through the addPresentedHandler callback of the currentDrawable in MTKView. Testing shows that T2 - T1 > 16.6ms (the Vsync period at 60Hz). This means that after the GPU rendering in MTLView is finished, the frame is not actually displayed at the next Vsync instruction but only at the Vsync instruction after that. I believe there is an extra 16.6ms of latency here, which I want to eliminate by adjusting the rendering mechanism. Observation from Instruments From Instruments, the Surface presentation aligns with the above test results. After the Metal encoder finishes, the Surface in Display switches only after the next-next Vsync instruction. See the image in the link for details. Questions According to a beginner's understanding, after MTKView's GPU rendering is finished, the next Vsync instruction should officially display (make it visible). However, this is not what is observed. Does the subview MTKView need to wait for another Vsync cycle to be drawn to the actual display buffer? The label updates its text at 60fps, so the entire interface should be displayed at 60fps. Is the content of MTKView not synchronized when the display happens? Explanation of the Reasoning Behind Some MTKView Code Details Changing from the default triple buffering to double buffering helps reduce the latency introduced by rendering. Not using MTKView's own scheduling mechanism but using manual triggering of the draw method is because MTKView's own scheduling mechanism is driven by CADisplayLink. Therefore, if a frame falls within a Vsync window, it needs to wait for the next Vsync window to trigger the draw operation, which introduces waiting latency.

The code is pretty simple kernel void naive( constant RunParams *param [[ buffer(0) ]], const device float *A [[ buffer(1) ]], // [N, K] device float *output [[ buffer(2) ]], uint2 gid [[ thread_position_in_grid ]]) { uint a_ptr = gid.x * param->K; for (uint i = 0; i < param->K; i++, a_ptr++) { val += A[b_ptr]; } output[ptr] = val; } when uint a_ptr = gid.x * param->K, the code got 150 GFLops when uint a_ptr = gid.y * param->K, the code got 860 GFLops param->K = 256; thread per group: [16, 16] I'd like to understand why the performance is so different, and how can I profile/diagnose this to help with further optimization.

The game physics work as expected using GTPK 2.0 using Crossover 24 or Whisky. However, using GPTK 2.1 with Crossover 25, the player and camera physics misbehave. See https://www.reddit.com/r/WWEGames/comments/1jx9mph/the_siamese_elbow/ and https://www.reddit.com/r/WWEGames/comments/1jx9ow4/camera_glitch/ Full video also linked in the Reddit post. I have also submitted this bug via the feedback assistant.

Hi, seems MSL is missing support for a clock() shader instruction available in other graphics APIs like Vulkan or OpenGL for example.. useful for counting cost in number of clock cycles of some code insider shader with much finer granularity than launching a micro kernel with same instructions and measuring cycles cost from CPU.. also useful for MoltenVK to support that extensions.. thanks..

I have run into an issue where I am trying to use atomic_float in a swift package but I cannot get things to compile because it appears that the Swift Package Manager doesn't support Metal 3 (atomic_float is Metal 3 functionality). Is there any way around this? I am using // swift-tools-version: 6.1 and my Metal code includes: #include <metal_stdlib> #include <metal_geometric> #include <metal_math> #include <metal_atomic> using namespace metal; kernel void test(device atomic_float* imageBuffer [[buffer(1)]], uint id [[ thread_position_in_grid ]]) { } But I get an error on the definition of atomic_float . Any help, one more importantly, where I could have found this information about this limitation, would be helpful. -RadBobby

In the Creating A 3D Application With Hydra Rendering tutorial on the Apple Developer website, on the last step where I execute this command: cmake -S ~/Users/macuser/CreatingA3DApplicationWithHydraRendering/ -B ~/Users/macuser/CreatingA3DApplicationWithHydraRendering/ I keep getting an error: CMake Error at CMakeLists.txt:5 (include): include could not find requested file: /Users/macuser/USDInstall/bin/pxrConfig.cmake I've tried to follow the instructions as mentioned in the README.md file included in the project files at least 5 times as well as moving the pxrConfig.cmake file around and copying it in different folders, then executed the command and was still unsuccessful into generating the proper file expected to compile and render the HydraPlayer renderer. How do I get cmake to generate the Xcode file to create the HydraPlayer renderer?

Hello! I'm a developer working on a plugin for the Elgato Stream Deck, called GPU Metrics. The plugin currently only works on Windows but I'd like to bring it to macOS. However, based on forum posts I've read (and StackOverflow) there isn't a very clear path to query GPU metrics like usage, temperature, used GPU memory, and power consumption. There are some tools out there that do similar things, but I wanted to see what would be the recommendation from Apple's engineering team to get this data via a public API. Requirements: Access GPU utilization, temperature, memory usage, power usage C/C++ based API for querying the metrics so I can expose the data to JavaScript via Node Addon No need to compatibile with Intel-based Macs, as Apple silicon will be fine for now Plugin GitHub Thank you! Noah

hi When analyzing our game using Instruments, I've always been confused about the two items "Drawable Present" and "Drawable Presented" in the GPU column. The timing of Drawable Present seems to be when the CPU layer calls commandbuffer:present, rather than when the actual encoding is completed on the GPU. Also, what does drawable presented specifically mean? In our case, when a CPU stall occurs, it appears that the vsync interval changes in the next frame, and a surface that has already been calculated is not displayed. Why is this happening?

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?