Rendering a windowed game in stereo

At a glance

Project structure

Source bundle/
└── RealityKit-Stereo-Rendering/
    ├── RealityKitStereoRenderingApp.swift
    ├── DeferredLighting/
    │   ├── Renderer/
    │   │   ├── Renderer.swift
    │   │   ├── Scene.swift
    │   │   ├── SinglePassDeferredRenderer.swift
    │   │   ├── TraditionalDeferredRenderer.swift
    │   │   └── Utilities/
    │   │       └── BufferView.swift
    │   ├── DeferredLightingView.swift
    │   └── Application/
    │       └── ViewController.swift
    ├── MetalVRREntity.swift
    ├── Settings.swift
    ├── HeadTracker.swift
    └── ViewableArea.swift

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 57 source declaration(s).

Overall architecture

flowchart LR
    N1["RealityKitStereoRenderingApp"]
    N2["WindowView"]
    N3["HeadPositionProvider"]
    N4["RealityKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

RealityKit-Stereo-Rendering/RealityKitStereoRenderingApp.swift:12 — architecture anchor

@main
struct MetalVRRPortalSampleApp: App {
    @Environment(\.openWindow) private var openWindow
    // ...
}

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
    Renderer o-- MTLRenderPassDescriptor : shadowRenderPassDescriptor
    Renderer o-- MTLCommandQueue : commandQueue
    Renderer o-- Callback : didBeginFrame
    Renderer o-- Callback : setGBufferTextures

Ownership evidence

RealityKit-Stereo-Rendering/DeferredLighting/Renderer/Renderer.swift:15 — stored dependency or nearest verified ownership anchor

    lazy var shadowRenderPassDescriptor: MTLRenderPassDescriptor = {
        let descriptor = MTLRenderPassDescriptor()
        descriptor.depthAttachment.texture = scene.shadowMap
        descriptor.depthAttachment.storeAction = .store
        return descriptor
    }()

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

RealityKit-Stereo-Rendering/DeferredLighting/DeferredLightingView.swift:23 — representative execution boundary

    override func setup() async {
        await super.setup()
        self.components.set(DeferredLightingComponent())
    }

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

RealityKit-Stereo-Rendering/DeferredLighting/Renderer/Renderer.swift:353 — representative type boundary

@objc protocol DrawableProviding {
    var viewCount: Int { get }
    // ...
}

The source explicitly defines local protocol relationships: ResolutionProbeGrid → RateFactorProviding, DeferredLightingEntity → DrawableProviding, DeferredLightingEntity → RenderDestination, MTKView → DrawableProviding, MTKView → RenderDestination.

Access control

Reference code

Packages/RealityKit-Assets/Sources/RealityKit-Assets/RealityKit-Assets.swift:11 — representative boundary

public let assetsBundle = Bundle.module

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: MetalVRRPortalSampleApp; Component: DeferredLightingComponent; Controller: ViewController; Provider: HeadPositionProvider; Renderer: Renderer, SinglePassDeferredRenderer, TraditionalDeferredRenderer; Scene: Scene; System: DeferredLightingSystem, ResolutionProbeSystem; View: BufferView, DeferredLightingView, SettingsView, WindowView.
• Protocols: DrawableProviding, RateFactorProviding, RenderDestination.
• Methods: beginFrame, beginDrawableCommands, endFrame, encodePass, encodeStage, encodeGBufferStage, encodeDirectionalLightingStage, encodeLightMaskStage.
• Files: RealityKit-Stereo-Rendering/DeferredLighting/Renderer/Renderer.swift, RealityKit-Stereo-Rendering/DeferredLighting/DeferredLightingView.swift, RealityKit-Stereo-Rendering/MetalVRREntity.swift, RealityKit-Stereo-Rendering/Settings.swift, RealityKit-Stereo-Rendering/DeferredLighting/Application/ViewController.swift, RealityKit-Stereo-Rendering/DeferredLighting/Renderer/Scene.swift.

Architecture takeaways

• RealityKitStereoRenderingApp is the main source-visible entry or composition anchor for this sample.
• Framework work reaches MetalKit, SwiftUI, RealityKit, simd 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.
• Local protocol relationships provide an explicit substitution boundary.

Source map

• Official Apple documentation