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RealityKit SIMD3<Float> precision decreases with distance?
The farther away the center of a large entity is, the less accurate the positioning is? For example I am changing only the y-axis position of an entity that is tens of meters long, but i notice x and z drifting slowly the farther away the center of the entity is. I would not expect the x and z to move. It might be compounding rounding errors somewhere, or maybe the RealityKit engine is deciding not to be super precise about distant objects? Otherwise I just have a bug somewhere.
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608
Mar ’25
Showing a MTLTexture on an Entity in RealityKit
Is there any standard way of efficiently showing a MTLTexture on a RealityKit Entity? I can't find anything proper on how to , for example, generate a LowLevelTexture out of a MTLTexture. Closest match was this two year old thread. In the old SceneKit app, we would just do guard let material = someNode.geometry?.materials.first else { return } material.diffuse.contents = mtlTexture Our flow is as follows (for visualizing the currently detected object): Camera-Stream -> CoreML Segmentation -> Send the relevant part of the MLShapedArray-Tensor to a MTLComputeShader that returns a MTLTexture -> Show the resulting texture on a 3D object to the user
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1.1k
Sep ’25
GameKit not working as expected in iOS 26.
I just upgraded my macOS, Xcode and Simulator all to the newest beta version 26. Then I found two issues when building my app with Xcode 26 and running it on simulator 26. The game center access point no longer shows up in the app. This is how it's configured in the past. And it still works on simulator 18.4 func authenticatePlayer() { GKAccessPoint.shared.location = .topTrailing self.localPlayer.authenticateHandler = { viewController, error in if let viewController = viewController { // can present Game Center login screen } else if self.localPlayer.isAuthenticated { // game can be started } else { // user didn't log in, continue the game without game center } } } After game ended, the leaderboard won't load. This is how it's implemented in the past. It's still working in simulator 18.4 struct GameCenterView: UIViewControllerRepresentable { @Environment(\.presentationMode) var presentationMode ... func makeUIViewController(context: Context) -> GKGameCenterViewController { let viewController = GKGameCenterViewController( leaderboardID: getLeaderBoardID(with: leaderBoardGameMode), playerScope: .global, timeScope: .allTime ) viewController.gameCenterDelegate = context.coordinator return viewController } func updateUIViewController(_ uiViewController: GKGameCenterViewController, context: Context) {} func makeCoordinator() -> Coordinator { Coordinator(self) } class Coordinator: NSObject, GKGameCenterControllerDelegate { let parent: GameCenterView init(_ parent: GameCenterView) { self.parent = parent } func gameCenterViewControllerDidFinish(_ gameCenterViewController: GKGameCenterViewController) { parent.presentationMode.wrappedValue.dismiss() } } }
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434
Sep ’25
RealityKit and USDZ: Winding Order Issue with Negatively Scaled Meshes
Hi all, I've encountered a potential issue with how the winding order of geometry is handled when their transformations involve negative scaling. I created a simple test asset, a single triangle, to demonstrate this. The triangle's vertices are defined in a counter-clockwise ("right-handed") winding order, and its transform has a negative scale on the X-axis. According to the OpenUSD specification, this negative determinant in the transformation matrix should effectively reverse the winding order of the geometry: However, any given gprim's local-to-world transformation can flip its effective orientation, when it contains an odd number of negative scales. This condition can be reliably detected using the (Jacobian) determinant of the local-to-world transform: if the determinant is less than zero, then the gprim's orientation has been flipped, and therefore one must apply the opposite handedness rule when computing its surface normals (or just flip the computed normals) for the purposes of hidden surface detection and lighting calculations. When I view the asset in tools like Blender or Preview on macOS, it behaves as expected. The triangle's effective orientation is flipped to CW. However, when the same asset is viewed in Reality Composer Pro or with QuickLook on iOS, its effective orientation remains CCW. In other words, the triangle faces the opposite direction. My questions for the community and Apple are: Is this behavior in RealityKit a known issue? If this is a known issue, is there official guidance for DCC tools on how to export USDZ assets to ensure they appear correctly in the Apple ecosystem? Any insights or recommendations would be greatly appreciated.
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963
Nov ’25
playSoundFileNamed not working on Tahoe?
I have published a number of games that use SpriteKit for everything important. Since the release of macOS Tahoe, I've had a lot of end user reports saying that sound effects have stopped working in many (but not all) of my titles. I'm not doing anything unusual here – typical code is: sndGameOver = [SKAction playSoundFileNamed:@"Audio/GameOver.wav" waitForCompletion:YES]; Then at the appropriate time: [self runAction:sndGameOver]; Has anyone else encountered this? The code still works fine on previous operating systems, and appears to be fine on iOS too. Has something changed in macOS Tahoe? I'm at a bit of a loss. There's nothing obviously different between the titles that do work and the titles that don't. Suggestions welcomed! Thanks
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1.2k
Nov ’25
How to use MTKTextureLoader to load png data
I am trying to load some PNG data with MTKTextureLoader newTextureWithData,but the result shows wrong at the alpha area. Here is the code. I have an image URL, after it downloads successfully, I try to use the data or UIImagePNGRepresentation (image), they all show wrong. UIImage *tempImg = [UIImage imageWithData:data]; CGImageRef cgRef = tempImg.CGImage; MTKTextureLoader *loader = [[MTKTextureLoader alloc] initWithDevice:device]; id<MTLTexture> temp1 = [loader newTextureWithData:data options:@{MTKTextureLoaderOptionSRGB: @(NO), MTKTextureLoaderOptionTextureUsage: @(MTLTextureUsageShaderRead), MTKTextureLoaderOptionTextureCPUCacheMode: @(MTLCPUCacheModeWriteCombined)} error:nil]; NSData *tempData = UIImagePNGRepresentation(tempImg); id<MTLTexture> temp2 = [loader newTextureWithData:tempData options:@{MTKTextureLoaderOptionSRGB: @(NO), MTKTextureLoaderOptionTextureUsage: @(MTLTextureUsageShaderRead), MTKTextureLoaderOptionTextureCPUCacheMode: @(MTLCPUCacheModeWriteCombined)} error:nil]; id<MTLTexture> temp3 = [loader newTextureWithCGImage:cgRef options:@{MTKTextureLoaderOptionSRGB: @(NO), MTKTextureLoaderOptionTextureUsage: @(MTLTextureUsageShaderRead), MTKTextureLoaderOptionTextureCPUCacheMode: @(MTLCPUCacheModeWriteCombined)} error:nil]; }] resume];
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666
May ’25
Game Center challenges and activities issues for released game
We have a released game in the App Store with Game Center Challenges. The challenges were working well in testing of the final version before the Game Center challenges went live. After release the activity that should take the player to the challenge in game results in this printout and we do not get informed by GKGameActivityListener of the activity happening in our code as we did before the Game Center challenges went live. “Invalid game activity definition. Failed to kick activity notification to GameKit. Error: Error Domain=GKErrorDomain Code=17 "(null)"” Also, Game Center reports that the are no challenges in GKChallengeDefinition.all even though there are ongoing challenges. The leaderboard results do get reported to Game Center though and show up as challenge entries in the Games app. At the moment we are trying to figure out if this is a problem on our end or a Game Center server issue.
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646
Sep ’25
Performance Regression: In iOS 18.2 3D rotation in volume rendering is not smooth as compared to iOS 18.1
We as a team of engineers work on an app intended to visualize medical images. The type of situations where the app is used involves time critical decision making for acute clinical conditions. Stability of the app and performance are of utmost importance and can directly help timely treatment action. The app we are developing uses multiple libraries and tools like vtk, webgl, opengl, webkit, gl-matrix etc. The problem specifically can be described as follows, it has been observed that when 3D volume is rendered in the app and we try to rotate the volume the rotation is slow, unresposive and laggy. Specifically, we have noticed that iOS 18.1 the volume rotation is much smoother as compared to latest iOS 18.2. Eariler, we have faced somewhat similar issue with iOS 17 but it got improved in iOS 18.1. This performance regression is affecting the user experience in our healthcare application. We have taken reference from the cornerstone.js code and you can reproduce the issue using the following example: https://www.cornerstonejs.org/live-examples/volumeviewport3d Steps to Reproduce: Load the above mentioned test example on an iPhone running version 18.2 using safari. Perform volume rendering using the provided dataset. Measure the time taken by volume for each rotate or drag action. Repeat the same steps on an iPhone running version 18.1 for comparison. Additional Information: Device Model Tested: iPhone12, iPhone13, iPhone14 iOS Version With Issue: 18.2 18.3(Beta) I would appreciate any insights or suggestions on how to address this performance regression. If additional information is needed, please let me know. Thank you.
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1k
Feb ’25
SpriteKit scene used as SCNView.overlaySKScene crashes due to SKShapeNode
I recently published my first game on the App Store. It uses SceneKit with a SpriteKit overlay. All crashes Xcode downloaded for it so far are related to some SpriteKit/SceneKit internals. The most common crash is caused by SKCShapeNode::_NEW_copyRenderPathData. What could cause such a crash? crash.crash While developing this game (and the BoardGameKit framework that appears in the crash log) over the years I experienced many crashes presumably caused by the SpriteKit overlay (I opened a post SceneKit app randomly crashes with EXC_BAD_ACCESS in jet_context::set_fragment_texture about such a crash in September 2024), and other people on the internet also mention that they experience crashes when using SpriteKit as a SceneKit overlay. Should I use a separate SKView and lay it on top of SCNView rather than setting SCNView.overlaySKScene? That seemed to solve the crashes for a guy on stackoverflow, but is it also encouraged by Apple? I know SceneKit is deprecated, but according to Apple critical bugs would still be fixed. Could this be considered a critical bug?
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MetalFX FrameInterpolator assertion: `Color texture width mismatch from descriptor` even when all texture sizes match
I am integrating MetalFX FrameInterpolator into a custom Unity RenderGraph–based render pipeline (C++ native plugin + C# render passes), and I am hitting the following assertion at runtime: /MetalFXDebugError.h:29: failed assertion `Color texture width mismatch from descriptor' What makes this confusing is that all input/output textures have the correct width and height, and they exactly match the values specified in the MTLFXFrameInterpolatorDescriptor. Setup Input resolution: 1024 x 512 Output resolution: 2048 x 1024 MTLFXTemporalScaler is created first and then passed into MTLFXFrameInterpolator The TemporalScaler and FrameInterpolator descriptors use the same input/output sizes and formats All Metal textures: Have no parentTexture Are 2D textures Match the descriptor sizes exactly (verified via logging) Texture bindings at encode time frameInterpolator.colorTexture = mtlTexColor; // 1024 x 512 frameInterpolator.prevColorTexture = mtlTexPrevColor; // 1024 x 512 frameInterpolator.motionTexture = mtlTexMotion; // 1024 x 512 frameInterpolator.depthTexture = mtlTexDepth; // 1024 x 512 frameInterpolator.uiTexture = mtlTexUI; // 2048 x 1024 frameInterpolator.outputTexture = mtlTexOutput; // 2048 x 1024 All widths/heights are logged and match: Color : 1024 x 512 (input) PrevColor : 1024 x 512 (input) Motion : 1024 x 512 (input) Depth : 1024 x 512 (input) UI : 2048 x 1024 (output) Output : 2048 x 1024 (output) The TemporalScaler works correctly on its own. The assertion only occurs when using FrameInterpolator. Important detail about colorTexture Originally, colorTexture was copied from BuiltinRenderTextureType.CurrentActive. After reading that this might violate MetalFX semantics, I changed the pipeline so that: colorTexture now comes from a dedicated private RenderGraph texture It is not the backbuffer It is not a drawable It is not used as a final output It is created before UI rendering Despite this, the assertion still occurs. Question Can uiTexture for MTLFXFrameInterpolator legally come from a texture copied from BuiltinRenderTextureType.CurrentActive? More generally: Are there additional hidden constraints on colorTexture / prevColorTexture (such as Metal usage, storageMode, aliasing, or hazard tracking) that could cause this assertion, even when sizes match? Does FrameInterpolator require colorTexture and prevColorTexture to be created in a very specific way (e.g. non-aliased, ShaderRead usage, identical Metal resource properties)? Any clarification on the exact semantic requirements for colorTexture, prevColorTexture, or uiTexture in MetalFX FrameInterpolator would be greatly appreciated.
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Sample code for WWDC25 Session
Hi! I watched the WWDC25 session "Bring your SceneKit project to RealityKit" which seemed like a great resource for those of us transitioning from the now-deprecated SceneKit framework. The session mentioned that the full sample code for the project would be available to download, but I haven't been able to find it in the Code section of the video page or in the Sample Code Library. Has the sample code been released yet? Having the project code would make it much easier to follow along with the RealityKit changes shown in the video. Thanks again for the great session.
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306
Jun ’25
Photogrammetry requiring lidar-capable phones, curious why
Hello! I'm currently building an app where I feed images into a Photogrammetry session to create a USDZ. Pretty straightforward, works great. We've recently started some testing on older devices, and have discovered that Photogrammetry is requiring devices that have LIDAR (we've seen some console logs referencing LIDAR if we stumble through a photogrammetry process without checking isSupported first) Judging from @swredcam's posting about ReefScan from November 24 (https://developer.apple.com/forums/thread/769221) it looks like Photogrammetry did work on those non-LIDAR devices. In my own testing on an iPhone 12 mini with iOS 17, PhotogrammetrySession says it's not supported. Since we're only feeding in a sequence of photos that have never had depth data, and they process fine on pro/max devices, we're curious why this would require a LIDAR sensor to work, when it seems like it did work without LIDAR in the past. Or is there some other limitation of non-pro devices that is causing photogrammetry to not be supported (especially on today's really powerful hardware) Thanks! ++md
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638
Mar ’25
Metal runtime shader library compilation and linking issue
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) } }
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933
Feb ’25
Xcode compile stucks(stops) when add new source files or add functions to previous files
Hello, we are working on a iOS game project, as progress, the project grows larger and larger. Because we are using other game dependencies and libraries, here larger and larger refers to the whole project, and our source files integrated and compiled by Xcode are not many. Now, it seems we hit a bottleneck, when I add new files or functions to the previous files to implement a new feature, Xcode compile stucks(stops), it's Indexing | Initializing datastore forever, cannot produce a final build. macOS 15.1, Xcode 16.2 Can you provide any solutions to solve this problem? Also submitted Feedback ID #FB18432749
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695
Aug ’25
RealityKit Instanced Rendering on visionOS
Hello, I've been trying to leverage instanced rendering in RealityKit on visionOS but have not had success. RealityKit states this is supported: https://developer.apple.com/documentation/realitykit/validating-usd-files https://developer.apple.com/videos/play/wwdc2021/10075/?time=1373 https://developer.apple.com/videos/play/wwdc2023/10099/?time=772 RealityKit Trace metrics Validating instancing is working: To test I made a base visionOS app with immersive space and the entity replaced with my test usdz file. I've been using the RealityKit Trace profiling template in xcode instruments in the immersive space and volume closed. This gets consistent draw call results. If I have a single sphere mesh with one material I get one draw call, but the number of draw calls grows linearly with mesh count no matter how my entity is configured. What I've tried Create a test scene in blender, export with instancing enabled Create a test scene in Reality Composer Pro using references Author usda files by hand based on the OpenUSD spec Programatically create a MeshResource with Contents at runtime References https://openusd.org/release/api/_usd__page__scenegraph_instancing.html https://developer.apple.com/documentation/realitykit/meshresource https://developer.apple.com/documentation/realitykit/meshresource/instance Thank you
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1.5k
Oct ’25
GKLocalPlayer save and fetch data to iCloud issue
Hi all I have two mystic issues with saving and fetching data to and from iCloud. Both repro only after first launch of an app. 1. [GKLocalPlayer fetchSavedGamesWithCompletionHandler:] After first attempt I can see 0 saved games (but i know that there is at least one saved game) and there is no any error. In case if I try fetch one more time (without any additional actions) even immediately after first attempt I receive saved games correctly (not 0) 2. [GKLocalPlayer saveGameData: withName: completionHandler:] After first attempt I can see error The requested operation could not be completed because local player has not been authenticated. In case if I try save one more time (without any additional actions) even immediately after first attempt I can save data successfully without any error I found the same issue in StackOverflow, but there are no fixes...
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1.5k
Feb ’25
Roblox freezing on MacOS 26.1 Beta
After updating to MacOS 26.1 I encountered an issue that Roblox tends to freeze quite often for 10 - 60 seconds at most, this is really annoying that it is doing this as i play the game a lot. My theory is that it is like a driver issue with metal or something, I have reinstalled MacOS, reinstalled the game and lowed the performance manually but nothing is working. Wondering if you could help, when it will be fixed and if others are having the same issue. Many thanks, William.
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825
Oct ’25