Default RealityKit application isn't working - ios

Question

When running the generated Augmented Reality app with RealityKit from Xcode, nothing appears on the screen and I'm getting weird logs on the console:
2020-09-16 16:54:29.246883+0200 TestAR[494:29654] Metal GPU Frame Capture Enabled
2020-09-16 16:54:29.247203+0200 TestAR[494:29654] Metal API Validation Enabled
2020-09-16 16:54:29.792709+0200 TestAR[494:29654] Compiler failed to build request
2020-09-16 16:54:29.792957+0200 TestAR[494:29654] [Graphics] makeRenderPipelineState failed [output of type ushort is not compatible with a MTLPixelFormatR16Float color attachement.].
2020-09-16 16:54:29.792989+0200 TestAR[494:29654] [Graphics] makeRenderPipelineState failed.
I have tried to run the app on my two devices and the result is the same. Also tried to use Xcode 12, same result. What's even more disturbing is that I got the app to work like 2 times on the 20+ tries at random without changing anything, just killing the app and restarting or closing xcode and restaring.
Here is the code, but this is just the basic generated code:
struct ContentView : View {
var body: some View {
return ARViewContainer().edgesIgnoringSafeArea(.all)
}
}
struct ARViewContainer: UIViewRepresentable {
func makeUIView(context: Context) -> ARView {
let arView = ARView(frame: .zero)
let boxAnchor = try! Experience.loadBox()
arView.scene.anchors.append(boxAnchor)
return arView
}
func updateUIView(_ uiView: ARView, context: Context) {}
}
At this point I don't really understand what I'm doing wrong, here are the additionnal informations:
macOS Catalina v10.15.5
iPhone X 13.5.1
iPhone X 13.7
iPhone 6S Plus 13.5.1
Xcode 11.7
Xcode 12

Answer 1

At first you have to make sure that you didn't change a content in AppDelegate.swift file. A window's root view controller must come from contentView:
let contentView = ContentView()
window.rootViewController = UIHostingController(rootView: contentView)
window.makeKeyAndVisible()
Solution I
Sometimes in Xcode you may observe a bug – your app can't be launched or run due to some errors found in intermediate compiled data folder. All you need to do is to empty a DerivedData directory.
For that in Finder just press a shortcut Cmd-Shift-G and specify the following path to get to desired directory:
~/Library/Developer/Xcode/DerivedData/
After the deletion of a content of DerivedData directory your compiled app must be working as expected.
Additional info about DerivedData:
DerivedData is a folder located in ~/Library/Developer/Xcode/DerivedData by default. It’s the location where Xcode stores all kinds of intermediate build results, generated indexes, etc. DerivedData location can be configured in Xcode preferences (Locations tab).
Solution II
If the above two steps didn't help, you should reinstall Xcode.