Altering RealityKit Rendering with Shader Functions

At a glance

Project structure

Source bundle/
└── Pop/
    ├── PopApp.swift
    ├── UI/
    │   ├── ContentView.swift
    │   ├── RealityView.swift
    │   └── RealityViewContainer.swift
    ├── ApplicationActions.swift
    ├── Entity+Utilities.swift
    └── Metal Shaders/
        ├── CustomMaterialHelpers.h
        ├── CustomMaterialHelpers.metal
        ├── DissolveSurfaceShader.metal
        ├── ExpandGeometryModifier.metal
        ├── UVHelpers.h
        └── UVHelpers.metal

Structure observations

• Architecturally prominent files are ranked from entry points and role-named declarations; resource-only paths are omitted.
• Primary languages: C/Objective-C header, Metal, Swift.
• The verified tree contains 4 project/configuration file(s) and 7 source declaration(s).

Overall architecture

flowchart LR
    N1["PopApp"]
    N2["ContentView"]
    N3["Coordinator"]
    N4["RealityKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

Pop/PopApp.swift:10 — architecture anchor

@main
@available(iOS 15.0, *)
struct PopApp: App {
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

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 realitykit.

Ownership and state

classDiagram
    ContentView *-- CGFloat : maxTapDistance
    ResetButton *-- String : title
    ResetButton *-- String : logMessage
    RealityView o-- ARCoachingOverlayView : coachingView

Ownership evidence

Pop/UI/ContentView.swift:16 — stored dependency or nearest verified ownership anchor

@available(iOS 15.0, *)
struct ContentView: View {
    let maxTapDistance = CGFloat(10)
    // ...
}

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

Pop/ApplicationActions.swift:21 — representative execution boundary

@available(iOS 15.0, *)
struct ApplicationActions {
    // ...
    let playerQueue = DispatchQueue(label: "com.apple.samplecode.player")
    // ...
}

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

Pop/PopApp.swift:12 — representative type boundary

@main
@available(iOS 15.0, *)
struct PopApp: App {
    // ...
            ContentView()
    // ...
}

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

Access control

Reference code

Pop/UI/RealityView.swift:60 — representative boundary

    public func userTapped(at point: CGPoint) {
        // ...
                print("Tapped entity is not a robot.")
        // ...
    }

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

Naming conventions

• Types: App: PopApp; Coordinator: Coordinator; View: ContentView, RealityView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: setup, userTapped, resetRobots, incrementPopProgress, initializeMetal, configureWorldTracking, setUpCoachingOverlay, layoutRobots.
• Files: Pop/PopApp.swift, Pop/UI/ContentView.swift, Pop/UI/RealityView.swift, Pop/UI/RealityViewContainer.swift, Pop/ApplicationActions.swift.

Architecture takeaways

• PopApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches RealityKit, metal_stdlib, SwiftUI, ARKit 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