Implementing special rendering effects with RealityKit postprocessing

At a glance

Project structure

Source bundle/
└── RealityKitPostProcessing/
    ├── AppDelegate.swift
    ├── ContentView.swift
    ├── Application State/
    │   ├── ApplicationState+Enums.swift
    │   └── ApplicationState.swift
    ├── RealityView/
    │   ├── RealityView.swift
    │   ├── RealityView+CoachingView.swift
    │   └── RealityViewContainer.swift
    ├── Kernel Functions/
    │   ├── NightVision.h
    │   ├── Pixelate.h
    │   └── CustomPostProcess.metal
    ├── ARView+Utilities.swift
    └── Bridging/
        └── RealityKitPostProcessing-Bridging-Header.h

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 3 project/configuration file(s) and 13 source declaration(s).

Overall architecture

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

Reference code

RealityKitPostProcessing/AppDelegate.swift:11 — architecture anchor

@main
class AppDelegate: UIResponder, UIApplicationDelegate {

    var window: UIWindow?

    func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {

        let contentView = ContentView()
        let window = UIWindow(frame: UIScreen.main.bounds)
        window.rootViewController = UIHostingController(rootView: contentView)
        self.window = window
        window.makeKeyAndVisible()
        return true
    }
}

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
    AppDelegate o-- UIWindow : window
    ContentView *-- ModeEntry : selection
    SelectionCell o-- ModeEntry : entry
    SelectionCell o-- ModeEntry : selectedEntry

Ownership evidence

RealityKitPostProcessing/AppDelegate.swift:14 — stored dependency or nearest verified ownership anchor

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    var window: UIWindow?
    // ...
}

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.

No source-visible execution, scheduling, or synchronization boundary was found in the indexed source.

@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.

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

RealityKitPostProcessing/AppDelegate.swift:12 — representative type boundary

@main
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
    var window: UIWindow?
    // ...
}

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

Access control

Reference code

RealityKitPostProcessing/RealityView/RealityView+Metal.swift:105 — representative boundary

    private func postProcessUsingMetalShader(context: ARView.PostProcessContext,
                                             pipeline: MTLComputePipelineState,
                                             parameterHandler: MetalParameterSetup?) {
        // ...
    }

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: Coordinator: Coordinator; Delegate: AppDelegate; View: ContentView, RealityView.
• Protocols: no local protocol declaration in the scanned source.
• Methods: application, postProcessSetupCallback, configureWorldTracking, setUpCoachingOverlay, loadScene, setupPostProcessing, postProcess, postEffectNone.
• Files: RealityKitPostProcessing/AppDelegate.swift, RealityKitPostProcessing/ContentView.swift, RealityKitPostProcessing/RealityView/RealityView.swift, RealityKitPostProcessing/RealityView/RealityViewContainer.swift, RealityKitPostProcessing/Application State/ApplicationState.swift.

Architecture takeaways

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