Transforming entities between RealityKit coordinate spaces

At a glance

Project structure

Source bundle/
└── CoordSpaceTransform/
    ├── AppModel.swift  # ImmersiveSpaceState, AppModel
    ├── VolumetricView.swift  # VolumetricView
    ├── ImmersiveView.swift  # ImmersiveView
    ├── CoordSpaceTransformApp.swift  # CoordSpaceTransformApp
    └── ToggleImmersiveSpaceButton.swift  # ToggleImmersiveSpaceButton

Structure observations

• The runtime boundary is WindowGroup + volumetric window + ImmersiveSpace; the tree is pruned to lifecycle, state, framework, rendering, and ECS files.
• The source is Swift; role-named types and feature folders separate the major responsibilities.

Overall architecture

flowchart LR
    CoordSpaceTransformApp_1["CoordSpaceTransformApp"]
    WindowGroup___volumetric_window___ImmersiveSpace_2["WindowGroup + volumetric window + ImmersiveSpace"]
    VolumetricView_3["VolumetricView"]
    AppModel_4["AppModel"]
    RealityKit_entity_graph_5["RealityKit entity graph"]
    SwiftUI_RealityKit_coordinate_conversion_6["SwiftUI/RealityKit coordinate conversion"]
    CoordSpaceTransformApp_1 --> WindowGroup___volumetric_window___ImmersiveSpace_2
    WindowGroup___volumetric_window___ImmersiveSpace_2 --> VolumetricView_3
    VolumetricView_3 --> AppModel_4
    AppModel_4 --> RealityKit_entity_graph_5
    RealityKit_entity_graph_5 --> SwiftUI_RealityKit_coordinate_conversion_6

Reference code

CoordSpaceTransform/CoordSpaceTransformApp.swift:12 — executable or app-lifecycle anchor.

struct CoordSpaceTransformApp: App {
    // ...
}

The diagram is a responsibility flow, not a claim that every adjacent node directly calls the next. It separates lifecycle, presentation, stable state, framework/session work, and the RealityKit entity graph.

Ownership and state

classDiagram
    CoordSpaceTransformApp *-- AppModel : appModel
    AppModel *-- Entity : volumeCubeLastSceneTransformEntity
    AppModel *-- Entity : volumeRootEntity
    AppModel *-- Entity : immersiveSpaceRootEntity

Ownership evidence

CoordSpaceTransform/CoordSpaceTransformApp.swift:14 — representative stored state or nearest verified lifecycle anchor.

    @State private var appModel = AppModel()
    
    /// The action that dismisses an immersive space.
    @Environment(\.dismissImmersiveSpace) private var dismissImmersiveSpace

    /// The action that presents an immersive space.
    @Environment(\.openImmersiveSpace) private var openImmersiveSpace

Ownership is intentionally narrow: environment, bindings, observed objects, weak links, and delegate callbacks do not prove lifetime ownership. Initialized stored services and wrapper-managed state do; entities added inside a RealityKit content closure belong to that entity graph.

Class and protocol design

The reviewed source defines no local substitution protocol. Its App, View, delegate, renderer, ARKit, and RealityKit conformances are framework-facing contracts, so this document does not label the whole app protocol-oriented.

Access control

No reviewed Swift access example uses fileprivate, private(set), public, open; declarations without a modifier are internal.

Reference code

CoordSpaceTransform/CoordSpaceTransformApp.swift:14 — representative visibility boundary.

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

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: App: CoordSpaceTransformApp; Model: AppModel; View: ImmersiveView, VolumetricView.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: updateTransformsWhileDragging, updateTransform, moveCubeFromImmersiveSpaceToVolumetricWindow, getDurationBasedOnDistance, makeCubeSubEntityOfVolumeRoot, createContentAndPositionAttachments, createCube, createVolumetricWindowCube.
• Files and folders use primary-type or responsibility names such as Views, Models, Rendering, Components, Systems, Packages, or feature names where those boundaries exist.

Architecture takeaways

• Treat CoordSpaceTransformApp as the owner of executable or scene lifecycle, not automatically as the owner of every entity created later.
• Keep view/controller input near presentation, but move sessions, reconstruction, capture, rendering, shared game state, or documents into stable owners when their lifetime exceeds one callback or render pass.

Source map

• Official Apple documentation