Altering RealityKit Rendering with Shader Functions

At a glance

Project structure

Source bundle/
└── Pop/
    ├── UI/
    │   ├── RealityViewContainer.swift  # RealityViewContainer, Coordinator
    │   ├── ContentView.swift  # ContentView, ContentView_Previews, ResetButton
    │   └── RealityView.swift  # RealityView
    ├── Metal Shaders/
    │   └── DissolveSurfaceShader.metal
    ├── PopApp.swift  # PopApp
    ├── ApplicationActions.swift  # ApplicationActions
    └── Entity+Utilities.swift

Structure observations

• The runtime boundary is WindowGroup; the tree is pruned to lifecycle, state, framework, rendering, and ECS files.
• The source is C/Objective-C header, Metal, Swift; role-named types and feature folders separate the major responsibilities.

Overall architecture

flowchart LR
    PopApp_1["PopApp"]
    WindowGroup_2["WindowGroup"]
    RealityView_3["RealityView"]
    Coordinator_4["Coordinator"]
    RealityKit_entity_graph_5["RealityKit entity graph"]
    RealityKit_custom_materials___Metal_6["RealityKit custom materials + Metal"]
    PopApp_1 --> WindowGroup_2
    WindowGroup_2 --> RealityView_3
    RealityView_3 --> Coordinator_4
    Coordinator_4 --> RealityKit_entity_graph_5
    RealityKit_entity_graph_5 --> RealityKit_custom_materials___Metal_6

Reference code

Pop/PopApp.swift:12 — executable or app-lifecycle anchor.

struct PopApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

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
    RealityView --> AnchorEntity : robotScene
    ApplicationActions --> AVAudioPlayer : whooshPlayer
    RealityView --> ARCoachingOverlayView : coachingView
    RealityView --> MTLDevice : device

Ownership evidence

Pop/UI/RealityView.swift:30 — representative stored state or nearest verified lifecycle anchor.

@available(iOS 15.0, *)
class RealityView: ARView {
    // ...
    var robotScene: AnchorEntity?
    // ...
}

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), open; declarations without a modifier are internal.

Objective-C/C header and implementation visibility is documented separately from Swift lexical access control.

Reference code

Pop/UI/RealityView.swift:90 — representative visibility boundary.

    private func incrementPopProgress(entity: Entity) async {
        // ...
    }

Logic ownership and placement

Design patterns

Naming conventions

• Role suffixes are evidence, not decoration: App: PopApp; Coordinator: Coordinator; View: ContentView, RealityView.
• Protocols: no app-defined protocol in the reviewed source.
• Commands use verb-led methods: makeUIView, updateUIView, makeCoordinator, setup, userTapped, resetRobots, incrementPopProgress, initializeMetal.
• 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 PopApp 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