Rendering a scene with deferred lighting in Swift

At a glance

Project structure

Source bundle/
├── Application/
│   ├── AppDelegate.swift
│   ├── ViewController.swift
│   └── WindowSceneDelegate.swift
└── Renderer/
    ├── Renderer.swift
    ├── Scene.swift
    ├── SinglePassDeferredRenderer.swift
    ├── TraditionalDeferredRenderer.swift
    ├── Utilities/
    │   ├── BufferView.swift
    │   └── Mesh/
    │       └── Mesh.swift
    ├── UtilityExtensions/
    │   └── Metal+Extensions.swift
    └── Shaders/
        ├── AAPLPointLights.metal
        └── AAPLShaderCommon.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 9 project/configuration file(s) and 28 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ViewController"]
    N3["Renderer"]
    N4["MetalKit / metal_stdlib APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

Application/AppDelegate.swift:16 — architecture anchor

#if os(iOS) || os(tvOS)
@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
                     configurationForConnecting connectingSceneSession: UISceneSession,
    // ...
}
#endif

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 Metal.

Ownership and state

classDiagram
    AppDelegate o-- NSWindow : window
    Renderer o-- MTLRenderPassDescriptor : shadowRenderPassDescriptor
    Renderer o-- DispatchSemaphore : inFlightSemaphore
    Renderer o-- MTLCommandQueue : commandQueue

Ownership evidence

Application/AppDelegate.swift:52 — stored dependency or nearest verified ownership anchor

#if os(iOS) || os(tvOS)
// ...
#elseif os(macOS)
@main
class AppDelegate: NSObject, NSApplicationDelegate {
    @IBOutlet var window: NSWindow!
    // ...
}
#endif

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

Renderer/Renderer.swift:23 — representative execution boundary

class Renderer: NSObject {
    // ...
    private let inFlightSemaphore: DispatchSemaphore
    // ...
}

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

Renderer/Utilities/RenderDestination.swift:13 — representative type boundary

protocol RenderDestination {
    var colorPixelFormat: MTLPixelFormat { get set }
    var depthStencilPixelFormat: MTLPixelFormat { get set }
}

The source explicitly defines local protocol relationships: MTKView → RenderDestination.

Access control

Reference code

Renderer/Renderer.swift:23 — representative boundary

class Renderer: NSObject {
    // ...
    private let inFlightSemaphore: DispatchSemaphore
    // ...
}

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: Controller: ViewController; Delegate: AppDelegate, WindowSceneDelegate; Renderer: Renderer, SinglePassDeferredRenderer, TraditionalDeferredRenderer; Scene: Scene; View: BufferView.
• Protocols: RenderDestination.
• Methods: application, applicationDidFinishLaunching, applicationWillTerminate, applicationShouldTerminateAfterLastWindowClosed, beginFrame, beginDrawableCommands, endFrame, encodePass.
• Files: Application/AppDelegate.swift, Renderer/Renderer.swift, Application/ViewController.swift, Application/WindowSceneDelegate.swift, Renderer/Scene.swift, Renderer/SinglePassDeferredRenderer.swift.

Architecture takeaways

• AppDelegate is the main source-visible entry or composition anchor for this sample.
• Framework work reaches MetalKit, metal_stdlib, Metal, UIKit 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