Diorama

At a glance

Project structure

Source bundle/
├── Diorama/DioramaApp.swift  # DioramaApp, AppDelegate
├── Diorama/ViewModel.swift  # ViewModel
├── Packages/RealityKitContent/Sources/RealityKitContent/PointOfInterestComponent.swift  # Region, PointOfInterestComponent
├── Packages/RealityKitContent/Sources/RealityKitContent/BillboardComponent.swift  # BillboardComponent
├── Diorama/ContentView.swift  # ContentView
├── Diorama/Components.swift  # PointOfInterestRuntimeComponent, ControlledOpacityComponent
├── Diorama/FlockingComponent.swift  # FlockingComponent
├── Diorama/FlockingSystem.swift  # FlockingSystem
└── Packages/RealityKitContent/Package.realitycomposerpro/ProjectData/main.json  # authored RealityKit content

Structure observations

• The runtime boundary is WindowGroup + ImmersiveSpace; the pruned tree lists only files that explain lifecycle, state, or framework integration.
• App code is split into role-named views, models, managers, providers, components, or systems.
• Authored .reality or Reality Composer Pro content is a real implementation boundary; Swift loads or drives it rather than reproducing its entity graph.

Overall architecture

flowchart LR
    DioramaApp_1["DioramaApp"]
    WindowGroup___ImmersiveSpace_2["WindowGroup + ImmersiveSpace"]
    ContentView_3["ContentView"]
    ViewModel_4["ViewModel"]
    RealityView_entity_graph_5["RealityView entity graph"]
    RealityKit_components_and_systems_6["RealityKit components and systems"]
    DioramaApp_1 --> WindowGroup___ImmersiveSpace_2
    WindowGroup___ImmersiveSpace_2 --> ContentView_3
    ContentView_3 --> ViewModel_4
    ViewModel_4 --> RealityView_entity_graph_5
    RealityView_entity_graph_5 --> RealityKit_components_and_systems_6

Reference code

Diorama/DioramaApp.swift:14 — the app or executable entry declares the outer scene lifecycle.

struct DioramaApp: App {
    // ...
}

The diagram is a responsibility flow, not a claim that every adjacent node directly calls the next. It keeps scene ownership, shared state, RealityKit content, and framework-provider work at separate levels.

Ownership and state

classDiagram
    DioramaApp *-- ViewModel : viewModel
    ContentView --> ViewModel : viewModel
    BillboardSystem *-- ARKitSession : arkitSession
    ViewModel --> Entity : rootEntity

Ownership evidence

Diorama/DioramaApp.swift:18 — representative stored state or the nearest verified lifecycle anchor.

@main
struct DioramaApp: App {
    // ...
    @State private var viewModel = ViewModel()
    // ...
}

Ownership here is deliberately narrow: @Environment and weak references are shared links, initialized @State or stored services are lifecycle ownership, and a RealityView content closure owns additions to its entity graph without making the SwiftUI view a reference-type owner.

Class and protocol design

The source defines no local substitution protocol in the reviewed boundary. Its protocol use is framework-facing (App, View, RealityKit/ARKit protocols, or platform adapters), so this document does not label the whole app protocol-oriented.

Access control

No reviewed declaration uses fileprivate, private(set), open; unmodified Swift declarations are internal.

Reference code

Diorama/DioramaApp.swift:18 — representative visibility boundary.

@main
struct DioramaApp: App {
    // ...
    @State private var viewModel = ViewModel()
    // ...
}

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: App: DioramaApp; ViewModel: ViewModel; Provider: AttachmentsProvider; Delegate: AppDelegate.
• ECS names pair data and behavior: components PointOfInterestRuntimeComponent, ControlledOpacityComponent, FlockingComponent, BillboardComponent; systems FlockingSystem, BillboardSystem, TrailAnimationSystem.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: applicationShouldTerminateAfterLastWindowClosed, updateScale, updateRegionSpecificOpacity, setupAudio, resetAudio, updateTerrainMaterial, opacity, gain.
• Files generally match their primary type; Views, Models, Managers, Providers, Components, Systems, and Packages folders describe architectural roles where present.

Architecture takeaways

• Treat DioramaApp as the owner of scene declarations, not as the owner of every RealityKit entity created later.
• Keep view-local interaction in SwiftUI, but move provider sessions, playback resources, shared game state, or transport state into a stable owner when their lifetime exceeds one render pass.
• Run ARKit providers for the scene lifetime and consume their asynchronous updates in cancellable tasks; map anchors to entities at the boundary.
• Use RealityKit components for per-entity data and systems for repeated simulation instead of a monolithic view model.
• Model immersive-space open, transition, and close states explicitly so windows and immersive content cannot drift apart.

Source map

• Official Apple documentation