Our app uses Metal for image processing. We have found that if our app (and its possible intensive image processing) is started quickly after user is logged in, then calls to Metal may be hanging/stuck for a good while. Example: it can take 1-2 minutes for something that usually takes 3-5 seconds! Metal threads are just hanging in a memmove... In Activity Monitor we see a lot of things are happening right after log-in. But why Metal calls are blocking for so long is unknown to us... The workaround is to wait a minute before we start our app and start intensive image processing using Metal. But hard to explain this workaround to end-users... It doesn't happen on all computers but fairly easy to reproduce on some computers. We are using macOS 15.3.1. M1/M3 Max. Any good ideas for how to proceed with this problem and possible reach out to Apple engineers? Thanks! :)

My app is running Compute Shaders that use non-uniform thread groups. When I run the app in the debugger with a simulator target the app crashes on encoder.dispatchThreads and the error message is: Dispatch Threads with Non-Uniform Threadgroup Size is not supported on this device. Previously the log output states that: Metal Shader Validation is unsupported for Simulator. However: When I stop the debugger and just run the app in the simulator without the debugger attached, the app just runs fine and does not crash. The SwiftUI Preview that also triggers the Compute Shader when preparing data also just runs fine without a crash. I can run and debug on a real device no problem - I just don't have all sizes available. Is there anything I need to check in my lldb/simulator configuration? It obviously does work, just the debugger cannot really deal with it? Any input would be nice as this really slows my down as I have to be extremely careful when debugging on the simulator.

After following the instructions here: https://developer.apple.com/metal/cpp/ I attempted building my project and Xcode presented several errors. In essence it's complaining about some redeclarations in the Metal-CPP headers. NSBundle.hpp and NSError.hpp are included in the metal-cpp/foundation directory from the metal-cpp download. Any help in getting these issues resolved is appreciated. Thanks!

I notice some metal-cpp classes have static funtion like static URL* fileURLWithPath(const class String* pPath); static class ComputePassDescriptor* computePassDescriptor(); static class AccelerationStructurePassDescriptor* accelerationStructurePassDescriptor(); which return a new object. these classes also provide 'alloc' and 'init' function to create object by default. for object created by 'alloc' and 'init', I use something like NS::Shaderd_Ptr or call release directly to free memory. Because 'alloc' and 'init' not explicit call on these static function. I wonder how to correctly free object created by these static function? did they managed by autorelease pool?

I'm implementing optimized matmul on metal: https://github.com/crynux-ai/metal-matmul/blob/main/metal/1_shared_mem.metal I notice that performance is significantly different with different threadgroup memory set in [computeEncoder setThreadgroupMemoryLength] All other lines are exactly same, the only difference is this parameter. Matmul performance is roughly 250 GFLops if I set 32768 (max bytes allowed on this M1 Max), but 400 GFLops if I set 8192. Why does this happen? How can I optimize it?

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.

Hello, Thank you for attending today’s Metal & game technologies group lab at WWDC25! We were delighted to answer many questions from developers and energized by the community engagement. We hope you enjoyed it and welcome your feedback. We invite you to carry on the conversation here, particularly if your question appeared in Slido and we were unable to answer it during the lab. If your question received feedback let us know if you need clarification. You may want to ask your question again in a different lab e.g. visionOS tomorrow. (We realize that this can be confusing when frameworks interoperate) We have a lot to learn from each other so let’s get to Q&A and make the best of WWDC25! 😃 Looking forward to your questions posted in new threads.

Hi, What's the best way to handle drastic changes in scene charateristics with the new MTLFXTemporalDenoisedScaler? Let's say a visible object of the scene radically changes its material properties. I can modify the albedo and roughness textures consequently. But I suspect the history will be corrupted. Blending visual information between the new frame and the previous ones might be a nonsense. I guess the problem should be the same when objects appear or disappear instantly. Is the upsacler manage these events for us (by lowering blending), or should we use the reactive or the denoise strength mask or something like that to handle them?

Im new in the Mac area but for sure not UE. Windows is a long process to packaging but it could be done. All the documentation for Epic and from the internet is basically non existent with exactly how to package a project within UE. I have Xcode installed which makes sense, agreed to terms and install for MacOS, I've been able to make a project for several weeks now and want to package for a test run for my friends to play on Windows. Now I just get this in the log: UATHelper: Packaging (Mac): ERROR: Failed to finalize the .app with Xcode. Check the log for more information UATHelper: Packaging (Mac): Trace written to file /Users/rileysleger/Library/Logs/Unreal Engine/LocalBuildLogs/UBA-ProjectNightTerror-Mac-Development.uba with size 12.6kb UATHelper: Packaging (Mac): Total time in Unreal Build Accelerator local executor: 8.12 seconds UATHelper: Packaging (Mac): Result: Failed (OtherCompilationError) UATHelper: Packaging (Mac): Total execution time: 9.71 seconds PackagingResults: Error: Failed to finalize the .app with Xcode. Check the log for more information UATHelper: Packaging (Mac): Took 9.77s to run dotnet, ExitCode=6 UATHelper: Packaging (Mac): UnrealBuildTool failed. See log for more details. (/Users/rileysleger/Library/Logs/Unreal Engine/LocalBuildLogs/UBA-ProjectNightTerror-Mac-Development.txt) UATHelper: Packaging (Mac): AutomationTool executed for 0h 0m 10s UATHelper: Packaging (Mac): AutomationTool exiting with ExitCode=6 (6) UATHelper: Packaging (Mac): RunUAT ERROR: AutomationTool was unable to run successfully. Exited with code: 6 PackagingResults: Error: AutomationTool was unable to run successfully. Exited with code: 6 PackagingResults: Error: Unknown Error This absolutely makes no sense to me. Anyone have ideas?

The sample code here, has code like: // Create a display link capable of being used with all active displays cvReturn = CVDisplayLinkCreateWithActiveCGDisplays(&_displayLink); But that function's doc says it's deprecated and to use NSView/NSWindow/NSScreen displayLink instead. That returns CADisplayLink, not CVDisplayLink. Also the documentation for that displayLink method is completely empty. I'm not sure if I'm supposed to add it to run loop, or what, after I get it. It would be nice to get an updated version of this sample project and/or have some documentation in NSView.displayLink

I am using Unreal Engine 5.6 on a MacBook Pro with an M3 chip and macOS 15.5. I’ve installed Xcode and accepted the license, but Unreal is not detecting the latest Metal Shader Standard (Metal v3.0). The maximum version Unreal sees is Metal v2.4, even though the hardware and OS should support Metal 3.0. I’ve also run sudo xcode-select -s /Applications/Xcode.app and accepted the license via Terminal. Is there anything in Xcode settings, SDK availability, or system permissions that could be preventing access to Metal 3.0 features?"

Hello! I'm developing a GPU (shader) language, where I aim to target multiple backends with a common frontend. I wanted to avoid having to round trip through Metal, and go straight to IR just like I have with SPIRV, in order to have a fast and efficient compilation process. I've been looking for a reference page where I can read about Metals IR, and as far as I'm aware, it exists, but I can't seem to find it anywhere. Furthermore, if such a reference is available, is there also a toolkit where I can run validation on the output IR, and perhaps even run optimizations, much like spv-tools for SPIRV? Any help would be appreciated! Thanks, Gustav

Our APP has integrated 3D function, in order to reduce the memory occupation of the APP in the background, we will uninstall the 3D after the APP enters the background. However, the uninstall also causes problems. When the uninstall process is executed in the background, the app will briefly trigger the background GPU rendering error warning with the error warning code: OGPUMetalError: Insufficient Permission (to submit GPU work from background) (00000006:kIOGPUCommandBufferCallbackErrorBackgroundExecutionNotPermitted) Execution of the command buffer was aborted due to an error during execution. Insufficient Permission (to submit GPU Work from background) (00000006: kIOGPUCommandBufferCallbackErrorBackgroundExecutionNotPermitted) excuse me this warning system will tighten APP permissions background?​ For example, limit or shorten the background survival time of the APP. In addition, will the background refresh function fail, resulting in the failure of Bluetooth Ibeacon activation?

Hi everyone, This project uses PyTorch on an Apple Silicon Mac (M1/M2/etc.), and the goal is to use the MPS backend for GPU acceleration, notes Apple Developer. However, the workflow depends on Float64 (double-precision) floating-point numbers for certain computations, notes PyTorch Forums. The error "Cannot convert a MPS Tensor to float64 dtype as the MPS framework doesn't support float64. Please use float32 instead" has been encountered, notes GitHub. It seems that the MPS backend doesn't currently support Float64 for direct GPU computation. Questions for the community: Are there any known workarounds or best practices for handling Float64-dependent operations when using the MPS backend with PyTorch? For those working with high-precision tasks on Apple Silicon, what strategies are being used to balance performance with the need for Float64? Offloading to the CPU is an option, and it's of interest to know if there are any specific techniques or libraries within the Apple ecosystem that could streamline this process while aiming for optimal performance. Any insights, tips, or experiences would be appreciated. Thanks in advance, Jonaid MacBook Pro M3 Max

Just wondering if anyone knows what it will take to hit greater than 60hz when targeting iPhone. If I set the preferredFramesPerSecond of an MTKView to 120, it works on the iPad, but on iPhone it never goes over 60hz, even with a simple hello triangle sample app... is this a limitation of targeting iPhone?

Can't seem to get the Metal HUD to display value range's (pre 26 Tahoe). The documented environment variable MTL_HUD_SHOW_VALUE_RANGE doesn't seem to work. https://developer.apple.com/documentation/xcode/monitoring-your-metal-apps-graphics-performance#Display-the-value-range-of-metrics Anyone having any luck?

I rewrote my graphics pipeline to use Load/Store better for clearing and don't care cases. All my tests pass, and in the Metal debugger, all the draw calls succeed. But when I present drawables (before [commandBuffer commit]) I only get a pink screen. I've tried everything I can think of: making sure the pixel formats are the same for the back buffer as my render targets, etc. But it's still pink. Could you point me in the right direction so I can fix this, or help describe why it's pink. That would be really helpful. Thank you, Brian Hapgood

I have a very basic usdz file from this repo I call loadTextures() after loading the usdz via MDLAsset. Inspecting the MDLTexture object I can tell it is assigning a colorspace of linear rgb instead of srgb although the image file in the usdz is srgb. This causes the textures to ultimately render as over saturated. In the code I later convert the MDLTexture to MTLTexture via MTKTextureLoader but if I set the srgb option it seems to ignore it. This significantly impacts the usefulness of Model I/O if it can't load a simple usdz texture correctly. Am I missing something? Thanks!

I have a bare-bones Metal app setup where I attach a CAMetalLayer to a window that inherits from a NSWindow with a custom delegate. Everything else is vanilla. I'm also using metal-cpp and metal shader converter. I'm running into a issue where the application runs fine in the beginning, but once I resize the window, it starts hitching. It turns out that [CAMetalLayer nextDrawable:] frequently (but not always) takes around a full second (plus or minus a few milliseconds) to return once drawableSize has been updated. I've tried setting allowsNextDrawableTimeout to false which doesn't work; it returns a valid drawable after a second instead of nil. Setting displaySyncEnabled to false reduces the likelihood of this happening to around 50% from 90%+ but does not eliminate it. Setting maximumDrawableCount to 2 or 3 does not seem to make a difference. By dumping the resource IDs of the returned textures I've noticed something interesting: Before resizing, the layer seems to shuffle between 2 textures or at least 2 resource IDs, but after resizing it starts to create new textures for each returned drawable. Occasionally it seems to reuse a previous resource ID, but it does not seem to have anything to do with whether the method returns quickly or not. Why does this happen, and how can I fix it? Should I create a new CAMetalLayer when resizing the window instead of updating drawableSize?

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[NSBundle allFrameworks]: unrecognized selector sent to instance NS::Bundle* Bundle = NS::Bundle::mainBundle(); Bundle->allFrameworks(); call to allFrameworks() and allBundles() will throw exception, but other functions work well.