Displaying a 3D environment through a portal

At a glance

Project structure

Source bundle/
├── RealityKit-UIPortal/
│   ├── RealityKit-UIPortal/
│   │   ├── App/
│   │   │   ├── EntryPoint.swift
│   │   │   ├── AppModel.swift
│   │   │   └── Info.plist
│   │   ├── Views/
│   │   │   ├── UIPortalView.swift
│   │   │   ├── ImmersiveView.swift
│   │   │   └── ToggleImmersiveSpace.swift
│   │   └── Extensions/
│   │       └── EnvironmentResource.swift
│   └── RealityKit-UIPortal.xcodeproj/
│       ├── .xcodesamplecode.plist
│       └── project.pbxproj
└── Configuration/
    └── SampleCode.xcconfig

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: Swift.
• The verified tree contains 4 project/configuration file(s) and 6 source declaration(s).

Overall architecture

flowchart LR
    N1["EntryPoint"]
    N2["UIPortalView"]
    N3["AppModel"]
    N4["SwiftUI / RealityKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

RealityKit-UIPortal/RealityKit-UIPortal/App/EntryPoint.swift:10 — architecture anchor

@main
struct EntryPoint: App {
    @State private var appModel = AppModel()

    var body: some Scene {
        WindowGroup {
            UIPortalView()
                .environment(appModel)
        }
        .windowResizability(.contentSize)

        // Defines an immersive space as a part of the scene.
        ImmersiveSpace(id: appModel.immersiveSpaceID) {
            ImmersiveView()
                .onAppear {
                    appModel.immersiveSpaceState = .open
                }
                .onDisappear {
                    appModel.immersiveSpaceState = .closed
                }
        }
        .immersionStyle(selection: .constant(.full), in: .full)
    }
}

Interpretation

The arrows summarize the source-visible entry, role-named types or folders, and framework direction; when nodes come from structural folders, the sequence is a high-level interpretation rather than proof that every adjacent node calls the next. Ownership is claimed only where the next section cites a stored property or assignment. The diagram is intentionally limited to the dominant path into visionOS.

Ownership and state

classDiagram
    EntryPoint *-- AppModel : appModel
    UIPortalView *-- Entity : root
    UIPortalView *-- ModelEntity : portalPlane

Ownership evidence

RealityKit-UIPortal/RealityKit-UIPortal/App/EntryPoint.swift:12 — stored dependency or nearest verified ownership anchor

@main
struct EntryPoint: App {
    @State private var appModel = AppModel()
    // ...
}

Composition arrows indicate a source-visible construction expression or locally owned value state; aggregation means the owner stores or receives a dependency without proving exclusive lifetime ownership.

Concurrency, scheduling, and thread safety

Evidence limit: actor isolation, async/await, or Task creation does not by itself prove background-thread execution; Sendable conformance alone does not prove thread-safe mutation.

@MainActor/MainActor.run, DispatchQueue.main, and RunLoop.main are reported as distinct isolation, queue, and event-loop mechanisms. A plain Task is kept separate from Task.detached; neither is labeled as a background thread.

Reference code

RealityKit-UIPortal/RealityKit-UIPortal/App/AppModel.swift:11 — representative execution boundary

@MainActor
@Observable
class AppModel {
    // ...
        case closed
    // ...
}

State propagation, frameworks, and dependencies

Evidence limit: an import proves a source-level compilation dependency at the cited line; it does not prove runtime use, architectural adoption, or whether a Swift package is a direct application dependency.

receive(on:) describes downstream delivery scheduling, while subscribe(on:) describes upstream subscription/request/cancel scheduling. An import Combine alone establishes neither behavior nor a Store, reducer, Redux, or other application architecture.

Class and protocol design

RealityKit-UIPortal/RealityKit-UIPortal/Views/UIPortalView.swift:11 — representative type boundary

struct UIPortalView: View {
    // ...
    @Environment(AppModel.self) private var appModel
    // ...
}

No local protocol conformance is claimed as protocol-oriented design; external framework conformances are listed only as dependencies.

Access control

Reference code

RealityKit-UIPortal/RealityKit-UIPortal/App/EntryPoint.swift:12 — representative boundary

@main
struct EntryPoint: App {
    @State private var appModel = AppModel()
    // ...
}

Swift declarations without a modifier are internal; explicit private, fileprivate, private(set), public, or open entries above are interpreted by language semantics. Objective-C/C samples instead rely on header and implementation boundaries, which are not equivalent to Swift lexical privacy.

Logic ownership and placement

Design patterns

Main application flow

sequenceDiagram
    participant ImmersiveView
    participant Entity
    participant EnvironmentResource
    participant iblEntity
    participant assetRoot
    participant root
    ImmersiveView->>Entity: Entity()
    ImmersiveView->>EnvironmentResource: EnvironmentResource()
    ImmersiveView->>Entity: Entity()
    ImmersiveView->>iblEntity: set()
    ImmersiveView->>assetRoot: set()
    ImmersiveView->>assetRoot: addChild()
    ImmersiveView->>root: addChild()

Reference code

RealityKit-UIPortal/RealityKit-UIPortal/Views/ImmersiveView.swift:51 — createEnvironment()

func createEnvironment(on root: Entity) async throws {
    /// The root entity for the box environment.
    let assetRoot = try await Entity(named: "CornellBox.usda")

    // Convert the image-based lighting file into a URL, and load it as an environment resource.
    guard let iblURL = Bundle.main.url(forResource: "TeapotIBL", withExtension: "exr") else {
        fatalError("Failed to load the Image-Based Lighting file.")
    }
    let iblEnv = try await EnvironmentResource(fromImage: iblURL)

    /// The entity to perform image-based lighting on the environment.
    let iblEntity = await Entity()

    /// The image-based lighting component that contains background and lighting information.
    var iblComp = ImageBasedLightComponent(source: .single(iblEnv))
    iblComp.inheritsRotation = true

    // Add the image-based lighting component to the entity.
    await iblEntity.components.set(iblComp)

    // Set up image-based lighting for the box environment.
    await assetRoot.components.set(ImageBasedLightReceiverComponent(imageBasedLight: iblEntity))

    // Add the image-based lighting entity to the box environment.
    await assetRoot.addChild(iblEntity)

    // Add the box environment to `root`.
    await root.addChild(assetRoot)
}

Naming conventions

• Types: Model: AppModel; View: ImmersiveView, UIPortalView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: createPortal, updatePortalSize, createEnvironment.
• Files: RealityKit-UIPortal/RealityKit-UIPortal/App/EntryPoint.swift, RealityKit-UIPortal/RealityKit-UIPortal/Views/UIPortalView.swift, RealityKit-UIPortal/RealityKit-UIPortal/App/AppModel.swift, RealityKit-UIPortal/RealityKit-UIPortal/Views/ImmersiveView.swift.

Architecture takeaways

• EntryPoint is the main source-visible entry or composition anchor for this sample.
• Framework work reaches SwiftUI, RealityKit, CoreImage through a deliberately small high-level chain; the detailed API graph remains inside the cited implementation files.
• Stored-property evidence identifies lifecycle collaboration; it does not by itself prove exclusive object ownership.
• Access-control conclusions separate verified language visibility from the likely design rationale.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation