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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So I've been trying out GPTK with Elite Dangerous Horizons game and it looks like from what I can tell. The VRAM keeps going up until it goes over the limit where it drops the FPS to 1-3 FPS and then crashes the game. From the Performance HUD I can see that it looks like when using GPTK, the VRAM usage just keeps climbing and I never saw it drop down at all. I did some limited testing, and from that I think I can conclude that it is probably not a VRAM leak, but it might be caching it. The reason for this is because I noticed that if I went back to the area that I've been before. It won't increase the VRAM usage.
So either there is something wrong with the freeing VRAM memory part, or it could be that GPTK might not be reporting the right amount of VRAM available to use? So maybe that's why it keeps allocating VRAM until it went out of memory and crashed the game.
Just to test, I did try running the game with DXVK+MoltenVK combo, and I can see that it works just fine. VRAM is being freed up when it's no longer used.
Is this a known issue in some games?
Hello,
I have noticed a performance drop on SpriteKit-based projects running on iOS 26.3.
The issue seems very similar to the issue reported on iOS 26.0, and later solved from iOS 26.2 beta 3:
https://developer.apple.com/forums/thread/800952?answerId=870617022#870617022
With 26.3, it seems a regression occured.
Below is the same SpriteKit scene used to test framerate on different devices:
import SpriteKit
import SwiftUI
class BareboneScene: SKScene {
override func didMove(to view: SKView) {
size = view.bounds.size
anchorPoint = CGPoint(x: 0.5, y: 0.5)
backgroundColor = .darkGray
let roundedSquare = SKShapeNode(rectOf: CGSize(width: 150, height: 75), cornerRadius: 12)
roundedSquare.fillColor = .systemRed
roundedSquare.strokeColor = .black
roundedSquare.lineWidth = 3
addChild(roundedSquare)
let action = SKAction.rotate(byAngle: .pi, duration: 1)
roundedSquare.run(.repeatForever(action))
}
}
struct BareboneSceneView: View {
var body: some View {
SpriteView(
scene: BareboneScene(),
debugOptions: [.showsFPS]
)
.ignoresSafeArea()
}
}
#Preview {
BareboneSceneView()
}
Running this very basic spritekit scene on my device and I can not reach an FPS of 60. Instead, it stalls around 40.
I see the same in my AppStore published SpriteKit games.
As you can see in the discussion of the linked forum topic, the regression has been noticed by others as well. Can you please look into this, and let us know if there is an outstanding action to resolve it already?
It's very problematic for published games suddenly dropping to 40FPS on even the most modern iOS devices.
When previewing the recording of gameplay the buttons to exit or save are unclickable behind the top bar clock and Wi-Fi/5G status bar. Which means that you have to quit the game in order to continue.
Tested on multiple devices.
Does anyone have a solution to this? At the moment we have disabled it altogether for iOS 26 users.
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()
}
}
}
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?
What is the recommended way to attach SwiftUI views to RealityKit entities on macOS, iOS, etc?
All the APIs seem to be visionOS only:
https://developer.apple.com/documentation/realitykit/realityviewattachments
https://developer.apple.com/documentation/realitykit/viewattachmentcomponent
https://developer.apple.com/documentation/realitykit/presentationcomponent
https://developer.apple.com/documentation/realitykit/imagepresentationcomponent
My only idea is to do it "manually" with a ZStack and RealityView somehow?
I submitted this as a feedback since it seemed like an oversight: FB18034856.
As part of the WWDC25 Keynote, a technology was announced that can present 2D images as 3D spatial scenes. This announcement is supported by a Press Release.
...developers can use the Spatial Scene API to make their app experience even more immersive. Zillow is taking advantage of the API for their Zillow Immersive app, allowing users to see images of homes and apartments with the rich depth and dimension that spatial scenes offer.
The feature also appears in the Photos App on iOS 26 Developer Beta 1. Tapping "Spatial Scene" on any photo opens a view of that photo with a parallax effect. I've searched the WWDC sessions and new documentation and have come up short. Reaching out here for help.
Is there any documentation for Spatial Scene API? Or any guidance on how to implement the spatial scene in iOS?
I have an AR game using ARKit with SceneKit that works just fine in iOS 17.
In the iOS 18 betas, the AR background image shows black instead of showing the real world. As a result there's no tracking and obviously the whole game is useless.
I narrowed down the issue to showing the Game Center Access Point.
My app has ViewController 1 (VC1) showing the main menu and that's where I want to show the GC Access Point. From there you open VC2 which shows a list of levels. Selecting any level will open VC3 which has the ARScene.
Following is the code I use to start Game Center in VC1:
GKLocalPlayer.local.authenticateHandler = { gcAuthVC, error in
let isGameCenterReady = (gcAuthVC == nil) && (error == nil)
if let viewController = gcAuthVC {
self.present (viewController, animated: true, completion: nil)
}
if error != nil {
print(error?.localizedDescription ?? "")
}
if isGameCenterReady {
GKAccessPoint.shared.location = .topLeading
GKAccessPoint.shared.showHighlights = true
GKAccessPoint.shared.isActive = true
}
}
When switching to VC2 I run GKAccessPoint.shared.isActive = false so that the Access Point will no longer show in any of the following VCs. I tried running it in VC1, VC2, and again in VC3 - it doesn't change anything. Once I reach VC3, the background is black.
If in VC1 I don't run GKAccessPoint.shared.isActive = true, so I don't activate the access point, the behavior is as follows:
If I wait until after the Game Center login animation completes and closes on its own and then I proceed to VC2 and VC3, the camera image will show correctly
If I quickly move to VC2 before the Game Center login animation has completed, so my code will close it by setting active = false, and then I continue to VC3, I will see the black background problem.
So it does look like activating the access point and then de-activating it causes the issue. BTW, if I activate the access point and leave it on in all VCs, the same black background issue persists.
Other than that, when I'm in VC3 with the black background and I switch to another app (so my game moves to the background), when it returns to the foreground, the camera suddenly shows the real world correctly!
I tried to manually reset the AR session by pausing and restarting it, but that didn't change anything. Also, when I check with the debugger, it looks like when the app comes back to the foreground it also doesn't run the session start code.
But something does seem to reset itself so I wonder what that is. Maybe I could trigger the same manually in my cdoe???
I repeat that everything works just fine in iOS 17 and below. This problem only started with the iOS 18 beta (currently on beta 5, but it started in some of the previous betas as well).
So could this be a bug in iOS 18?
As a workaround I could check the iOS version and if it's iOS18 not activate the access point, hoping that the user will not jump to VC2 too quickly, and show my own button which will open Game Center. But I'd rather give the users the full experience with their own avatar and the highlights showing up. Plus, certainly some users will move quickly to VC2 and that will be an awful experience.
Any help would be greatly appreciated. Thanks!
A bit of background on what our app is doing:
We have a RealityKit ARView session running.
During this period we place objects in RealityKit.
At some point user can "take photo" and we use session.captureHighResolutionFrame to capture a frame.
We then use captured frame and frame.camera.projectPoint to project my objects back to 2D
Issue we found is that on devices that have iOS26, first photo user takes and the first frame received from session.captureHighResolutionFrame gives incorrect CGPoint for frame.camera.projectPoint. If user takes the second photo with the same camera phostion, second frame received from session.captureHighResolutionFrame gives correct CGPoint for frame.camera.projectPoint
I notices some difference between first and subsequent frames that i believe is corresponding with the issue. Yaw value of camera (frame.camera.eulerAngles.y) on first frame is not correct ( inconsistent with any subsequent frame)
I also created a small example app and i followed Building an Immersive Experience with RealityKit example to create it. The issue exists in this app for iOS26, while iOS18.* has consistent values between first and subsequent captured frames.
Note:
The yaw value seems to differ more if we start session in portrait but take photo in landscape.
Example result for 3 captured frames:
Frame captured with yaw: 1.4855177402496338
Frame captured with yaw: -0.08803760260343552
Frame captured with yaw: -0.08179682493209839
Example code:
class CustomARView: ARView, ARSessionDelegate {
required init(frame: CGRect) { super.init(frame: frame) }
required init?(coder decoder: NSCoder) { fatalError("init(coder:) has not been implemented")}
func setup() {
let singleTap = UITapGestureRecognizer(target: self, action: #selector(handleTap))
addGestureRecognizer(singleTap)
}
@objc
func handleTap(_ gestureRecognizer: UIGestureRecognizer) {
Task {
do {
let frame = try await session.captureHighResolutionFrame()
print("Frame captured with yaw: \(Double(frame.camera.eulerAngles.y))")
} catch { }
}
}
}
struct CustomARViewUIViewRepresentable: UIViewRepresentable {
func makeUIView(context: Context) -> some UIView {
let arView = CustomARView(frame: .zero)
arView.setup()
return arView
}
func updateUIView(_ uiView: UIViewType, context: Context) { }
}
struct ContentView: View {
var body: some View {
CustomARViewUIViewRepresentable()
.frame(maxWidth: .infinity, maxHeight: .infinity)
.ignoresSafeArea()
}
}
Hello,
I recently watched the WWDC2025 session titled “Combine Metal 4 machine learning and graphics” (https://developer.apple.com/videos/play/wwdc2025/262/ ), and I’m very excited about the new Metal 4 features that integrate machine learning with graphics—such as neural ambient occlusion, shader-based ML inference, and the use of MTLTensor and MTL4MachineLearningCommandEncoder.
While the session includes helpful code snippets and a compelling debug demo (e.g., the neural ambient occlusion example), the implementation details are not fully shown, and I haven’t been able to find a complete, runnable sample project that demonstrates end-to-end integration of ML and rendering in Metal 4.
Would Apple be able to provide a full, working example—such as an Xcode project—that shows how to:
Export a model to an .mlpackage,
Convert it to an .mtlpackage,
Use MTL4MachineLearningCommandEncoder alongside render passes,
Or embed small neural networks directly in shaders using Shader ML?
Having such a sample would greatly help developers like me adopt these powerful new capabilities correctly and efficiently.
Thank you very much for your time and support!
Best regards,
I noticed that when the render command encoder adds no draw calls an apps memory usage seems to grow unboundedly. Using a super simple MTKView-based drawing with the following delegate (code at end).
If I add the simplest of draw calls, e.g., a single vertex, the app's memory usage is normal, around 100-ish MBs.
I am attaching a couple screenshot, one from Xcode and one from Instruments.
What's going on here? Is this an illegal program? If yes, why does it not crash, such as if the encode or command buffer weren't ended.
Or is there some race condition at play here due to the lack of draws?
class Renderer: NSObject, MTKViewDelegate {
var device: MTLDevice
var commandQueue: MTL4CommandQueue
var commandBuffer: MTL4CommandBuffer
var allocator: MTL4CommandAllocator
override init() {
guard let d = MTLCreateSystemDefaultDevice(),
let queue = d.makeMTL4CommandQueue(),
let cmdBuffer = d.makeCommandBuffer(),
let alloc = d.makeCommandAllocator()
else {
fatalError("unable to create metal 4 objects")
}
self.device = d
self.commandQueue = queue
self.commandBuffer = cmdBuffer
self.allocator = alloc
super.init()
}
func mtkView(_ view: MTKView, drawableSizeWillChange size: CGSize) {}
func draw(in view: MTKView) {
guard let drawable = view.currentDrawable else { return }
commandBuffer.beginCommandBuffer(allocator: allocator)
guard let descriptor = view.currentMTL4RenderPassDescriptor,
let encoder = commandBuffer.makeRenderCommandEncoder(
descriptor: descriptor
)
else {
fatalError("unable to create encoder")
}
encoder.endEncoding()
commandBuffer.endCommandBuffer()
commandQueue.waitForDrawable(drawable)
commandQueue.commit([commandBuffer])
commandQueue.signalDrawable(drawable)
drawable.present()
}
}
Topic:
Graphics & Games
SubTopic:
Metal
In SceneKit, when creating an .scn file from a rigged model, the framework created an SCNNode for each bone/joint, so you could add and remove child nodes directly to and from joints, and like any other SCNNode, you could access world position and world orientation for each joint. The analog would be for joints to be accessible as child entities of a ModelEntity in RealityKit. I am unable to proceed with migrating my project from SceneKit because of this, as there does not seem to be a way to even access the true world position of a joint with the current jointNames/jointTransforms paradigm.
The translation information from the given transforms is insufficient to determine the location of a joint at any given time, and other approaches like creating a GeometricPin for the given joint name and attaching it to another entity do not seem to work. So conveniently being able to attach an item to the hand of a rigged model was trivial in SceneKit and now feels impossible in RealityKit.
I am not the first person to notice this, and am feeling demoralized about proceeding with RealityKit with such a critical piece of functionality blocked
https://stackoverflow.com/questions/76726241/how-do-i-attach-an-entity-to-a-skeletons-joint-in-realitykit
Will this be addressed in some way?
We're using RealityKit to create a science education AR app for iOS, iPadOS, and visionOS.
In the WWDC25 session video "Bring your SceneKit project to RealityKit" https://developer.apple.com/videos/play/wwdc2025/288 at 8:15, it's explained that when using RealityKit, RealityView should be used in all cases, whereas in the past, SceneKit required SCNView, SceneView, or ARSCNView, depending on an app's requirements.
Because the initial development of our app on iOS predates iOS 18's RealityView, our app currently uses ARView to render RealityKit AR content on iOS and iPadOS.
Is it recommended that we migrate to RealityView, or can we safely continue using our existing ARView implementation? We'd prefer to avoid unnecessary development cost.
If migrating from ARView to RealityView is recommended, what specific benefits should we expect from this transition?
Thank you.
I'm an iOS developer, and I've been testing our app in iOS 18.0 Beta. I noticed that there's a problem with the font rendering, and after troubleshooting, I've found out that it's caused by the removal of the PingFang.ttc font in 18.0.
I would like to ask the reason for removing this font file and which font should be used to display Chinese in the future?
My test device is an iPhone 11 Pro and the system version is iOS 18.0 (22A5297). I have also tested Beta 1 and it has the same issue.
In previous versions of the system, the PingFang font is located in this directory /System/Library/Fonts/LanguageSupport/PingFang.ttc. But in iOS 18.0, the font file in this directory has become Kohinoor.ttc, and I've tested that this font can't display Chinese either.
I traversed the following system font directories and could not find the PingFang.ttc font file.
/System/Library/Fonts/AppFonts
/System/Library/Fonts/Core
/System/Library/Fonts/CoreAddition
/System/Library/Fonts/CoreUI
/System/Library/Fonts/LanguageSupport
/System/Library/Fonts/UnicodeSupport
/System/Library/Fonts/Watch
Looking for answers, thanks for the help!
I'm working on an application for viewing AMF models on macOS, using RealityKit. AMF supports several different ways to color models, including per-vertex color (where the color of a triangle is interpolated from vertex to vertex) as well as per-face color (where the color of the triangle is the same across the entire face).
I'm trying to figure out how to support those color models using a RealityKit mesh. Apple's documentation (https://developer.apple.com/documentation/realitykit/modifying-realitykit-rendering-using-custom-materials) talks about per-vertex colors, but I haven't found a way to create a mesh that includes per-vertex colors, other than use a texture map (which might be the correct solution).
Can someone give me some pointers?
The following code using the new GestureComponent demonstrates inconsistency. The tap gesture prints output, but the drag gesture does not.
I already checked this post, which points to this seemingly outdated sample code
I assume that example is deprecated in favour of the now built in version of GestureComponent.
Nonetheless, there are no compiler warnings or errors, it just fails silently.
TapGesture, LongPressGesture, MagnifyGesture, RotateGesture all work, so this feels like an oversight.
RealityView { content in
let testEntity = ModelEntity(mesh: .generateBox(size: .init(x: 1, y: 1, z: 1)))
testEntity.position = SIMD3<Float>(0,0,-1)
testEntity.components.set(InputTargetComponent())
testEntity.components.set(CollisionComponent(
shapes: [.generateBox(size: .init(x: 1, y: 1, z: 1))]
))
let testGesture = TapGesture()
.onEnded { value in
print("Tapped")
}
testEntity.components.set(GestureComponent(testGesture))
let dragGesture = DragGesture()
.onEnded { value in
print("Dragged")
}
testEntity.components.set(GestureComponent(dragGesture))
content.add(testEntity)
}
Hi all,
I’m running into an issue when trying to reconstruct a 3D model using PhotogrammetrySession on macOS from a set of images captured via the iOS Object Capture sample app, specifically in Area mode.
When I attempt to create the model from these images (using the raw Images/ folder exported directly from the capture session), I get the following errors:
ERROR cv3dapi.pg: Internal error codes (2): 4011 4012
WARN cv3dapi.pg: Internal warning codes (1): 4507
Output error with code = -15
requestError: CoreOC.PhotogrammetrySession.Error.processError
I use the "Images" directory directly exported from Object Capture with my iphone 12 pro max (has lidar) set to "area mode" in the object capture app
here is an example heic image metadata from the sequence.
heif-info Images/00044.869568833.HEIC
MIME type: image/heic
main brand: heic
compatible brands: mif1, MiHE, MiPr, miaf, MiHB, heic
image: 3024x4032 (id=49), primary
tiles: 6x8, tile size: 512x512
colorspace: YCbCr, 4:2:0
bit depth: 8
thumbnail: 240x320
color profile: nclx
alpha channel: no
depth channel: yes
size: 192x256
bits per pixel: 8
z-near: 1.173828
z-far: 2.552734
d-min: undefined
d-max: undefined
representation: uniform Z
metadata:
Exif: 960 bytes
uri /tag:apple.com,2023:ObjectCapture#CameraTrackingState: 4 bytes
uri /tag:apple.com,2023:ObjectCapture#CameraCalibrationData: 1015 bytes
uri /tag:apple.com,2023:ObjectCapture#ObjectTransform: 48 bytes
uri /tag:apple.com,2023:ObjectCapture#ObjectBoundingBox: 48 bytes
uri /tag:apple.com,2023:ObjectCapture#RawFeaturePoints: 832 bytes
uri /tag:apple.com,2023:ObjectCapture#PointCloudData: 23984 bytes
uri /tag:apple.com,2023:ObjectCapture#BundleVersion: 5 bytes
uri /tag:apple.com,2023:ObjectCapture#SegmentID: 4 bytes
uri /tag:apple.com,2024:ObjectCapture#SessionUUID: 36 bytes
uri /tag:apple.com,2024:ObjectCapture#CaptureMode: 4 bytes
uri /tag:apple.com,2023:ObjectCapture#Feedback: 4 bytes
uri /tag:apple.com,2023:ObjectCapture#WideToDepthCameraTransform: 48 bytes
uri /tag:apple.com,2023:ObjectCapture#TemporalDepthPointClouds: 864026 bytes
transformations:
angle (ccw): 270
region annotations:
none
properties:
camera intrinsic matrix:
focal length: 2813.695557; 2813.695557
principal point: 1522.338502; 2002.843018
skew: 0.000000
camera extrinsic matrix:
rotation matrix:
-0.695 0.344 -0.632
0.007 -0.875 -0.483
-0.719 -0.340 0.606
Questions:
• What do internal error codes 4011 and 4012 refer to?
• Is there something specific about Area mode captures that require preprocessing before they’re compatible with PhotogrammetrySession?
• Has anyone successfully reconstructed a model from an Area mode session using the stock Apple tools?
NOTE: I can provide the folder of images for debugging if that would help!
My goal is to print a debug message from a shader. I follow the guide that orders to set -fmetal-enable-logging metal compiler flag and following environment variables:
MTL_LOG_LEVEL=MTLLogLevelDebug
MTL_LOG_BUFFER_SIZE=2048
MTL_LOG_TO_STDERR=1
However there's an issue with the guide, it's only covers Xcode project setup, however I'm working on a Swift Package. It has a Metal-only target that's included into main target like this:
targets: [
// A separate target for shaders.
.target(
name: "MetalShaders",
resources: [
.process("Metal")
],
plugins: [
// https://github.com/schwa/MetalCompilerPlugin
.plugin(name: "MetalCompilerPlugin", package: "MetalCompilerPlugin")
]
),
// Main target
.target(
name: "MegApp",
dependencies: ["MetalShaders"]
),
.testTarget(
name: "MegAppTests",
dependencies: [
"MegApp",
"MetalShaders",
]
]
So to apply compiler flag I use MetalCompilerPlugin which emits debug.metallib, it also allows to define DEBUG macro for shaders. This code compiles:
#ifdef DEBUG
logger.log_error("Hello There!");
os_log_default.log_debug("Hello thread: %d", gid);
// this proves that code exectutes
result.flag = true;
#endif
Environment is set via .xctestplan and valideted to work with ProcessInfo. However, nothing is printed to Xcode console nor to Console app.
In attempt to fix it I'm trying to setup a MTLLogState, however the makeLogState(descriptor:) fails with error:
if #available(iOS 18.0, *) {
let logDescriptor = MTLLogStateDescriptor()
logDescriptor.level = .debug
logDescriptor.bufferSize = 2048
// Error Domain=MTLLogStateErrorDomain Code=2 "Cannot create residency set for MTLLogState: (null)" UserInfo={NSLocalizedDescription=Cannot create residency set for MTLLogState: (null)}
let logState = try! device.makeLogState(descriptor: logDescriptor)
commandBufferDescriptor.logState = logState
}
Some LLMs suggested that this is connected with Simulator, and truly, I run the tests on simulator. However tests don't want to run on iPhone... I found solution running them on My Mac (Mac Catalyst). Surprisingly descriptor log works there, even without MTLLogState. But the Simulator behaviour seems like a bug...
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?