Manipulating models with RealityKit

At a glance

Project structure

Source bundle/
└── ModelManipulator/
    ├── Models/
    │   ├── AppModel.swift  # AppModel, ImmersiveSpaceState, ViewState
    │   └── ClippingController.swift  # ClippingController
    ├── Systems/
    │   └── ClippingTransformSyncSystem.swift  # ClippingTransformSyncSystem
    ├── ModelManipulatorApp.swift  # ModelManipulatorApp
    ├── Views/
    │   └── ContentView.swift  # ContentView
    └── Components/
        ├── ClippingBoundsCacheComponent.swift  # ClippingBoundsCacheComponent, ClippingState
        └── ClippingTransformSyncComponent.swift  # ClippingTransformSyncComponent

Structure observations

• The runtime boundary is WindowGroup + 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
    ModelManipulatorApp_1["ModelManipulatorApp"]
    WindowGroup___ImmersiveSpace_2["WindowGroup + ImmersiveSpace"]
    ContentView_3["ContentView"]
    AppModel_4["AppModel"]
    ClippingController_5["ClippingController"]
    RealityKit_entity_graph_6["RealityKit entity graph"]
    RealityKit_components_and_systems_7["RealityKit components and systems"]
    ModelManipulatorApp_1 --> WindowGroup___ImmersiveSpace_2
    WindowGroup___ImmersiveSpace_2 --> ContentView_3
    ContentView_3 --> AppModel_4
    AppModel_4 --> ClippingController_5
    ClippingController_5 --> RealityKit_entity_graph_6
    RealityKit_entity_graph_6 --> RealityKit_components_and_systems_7

Reference code

ModelManipulator/ModelManipulatorApp.swift:11 — executable or app-lifecycle anchor.

struct ModelManipulatorApp: 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
    ModelManipulatorApp *-- AppModel : appModel
    AppModel --> Entity : modelEntity
    ContentView o-- AppModel : appModel
    ModelManipulatorApp o-- ScenePhase : scenePhase

Ownership evidence

ModelManipulator/ModelManipulatorApp.swift:12 — representative stored state or nearest verified lifecycle anchor.

    @State private var appModel = AppModel()

    @Environment(\.dismissImmersiveSpace) private var dismissImmersiveSpace
    @Environment(\.dismissWindow) private var dismissWindow
    @Environment(\.openImmersiveSpace) private var openImmersiveSpace
    @Environment(\.openWindow) private var openWindow
    @Environment(\.scenePhase) private var scenePhase

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, public, open; declarations without a modifier are internal.

Reference code

ModelManipulator/Models/AppModel.swift:28 — representative visibility boundary.

    private(set) var isModelExpanded = false
    /// A Boolean value that indicates whether the model supports expansion into component parts.
    var isModelExpandable: Bool { modelEntity?.assemblyParent != nil }

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: App: ModelManipulatorApp; Model: AppModel; Controller: ClippingController; System: ClippingTransformSyncSystem; Component: ClippingBoundsCacheComponent, ClippingTransformSyncComponent.
• ECS names pair data and behavior: components ClippingBoundsCacheComponent, ClippingTransformSyncComponent; systems ClippingTransformSyncSystem.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: handleClippingStateChange, presentFileImporter, reset, selectDefaultModel, selectModel, setupClippingObservation, toggleModelExpansion, toggleModelLock.
• 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 ModelManipulatorApp 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.
• Use components for per-entity data and systems for repeated simulation instead of centralizing every update in a view model or controller.
• Tie asynchronous session/output consumers to an explicit owner so cancellation and teardown follow the same lifecycle.

Source map

• Official Apple documentation