use an App Group to share across you app and extension

curious why you want to roll your own, rather than use Apple's implementation?

You must specify the bundle ID as the container identifier when instantiating your CKContainer.

Yes. surface geometry can be retrieved textures on geometries can be drawn/animated hand position can be retrieved its all possible

basically, yes, you need to upload the records to the public database once, such that subsequent devices can read them. Whether you do that thru the CloudKit console, or you write code in an app to upload/save is up to you.

Yes. the current design of NSPersistentCloudKitContainer is to sync everything. There are other sync engines available between CoreData and CloudKit, such as CKSyncEngine in iOS 17, and open source sun engines like CloudCore, which might provide more fine-grain control over sync. And of course, you can always write your own that best suits your needs.

unfortunately, I have written ton of functionality based on the CloudKit DiscoverUser functionality, and it all appears to be deprecated in iOS 17, with no new APIs to replace them. The sample code "Sharing CloudKit Data with Other iCloudUsers" doesn't address this at all.

the persistentContainer.viewContext can only get and set records in the main thread, but if I'm reading your code correctly, you're dropping into a task (background thread). better to use persistentContainer.performBackgroundTask { backgroundContext in … } and pass the background context to all your functions.

it sure does look like CloudKit is trying to push a record containing an unidentified field: "Cannot create or modify field 'CD_data_ckAsset' in record 'CD_ImageData' in production schema" While you may think all your image files are < 1Mb, Core Data may still be using external files in some edge cases. You could run your app in dev mode, add a very large image > 1mb, and have it sync, then see if there are schema changes to be pushed from dev to prod?

file a bug report!!!

file a bug report!

public asset storage (along with a variety of other capped resources) varies over time based on the number of active users of your app. You can find your current usage and limits in the CloudKit Dashboard > Telemetry > Usage Here's mine from one of my apps…

the system will ask the user for permission only once on your behalf. after that, you can check the status of the account, and if its disabled, display a UI directing the user to Settings to change the permission.

The short answer is, yes this is very possible. Years ago I ported an open-source particle emitter system into SceneKit and Metal using a SCNNode renderDelegate. Your code snippets above don't show setting the colorAttachments or depthAttachmentPixelFormat on the MTLRenderPipelineDescriptor?

As you have discovered, you cannot ignore the threading requirements of CoreData or SwiftUI. If you retrieve objects in a background context/thread, you cannot access them in the main thread (ie SwiftUI). How many FRCs are you instantiating? Can you do updates with one set of FRCs in background contexts, and then use another set in the viewContext? Have you tried setting the batching levels on your FRCs?