Creating a fog effect using scene depth

At a glance

Project structure

Source bundle/
├── ARDepthDataExample/
│   ├── Renderer.swift
│   ├── AppDelegate.swift
│   ├── ViewController.swift
│   ├── ARDepthDataExampleSwift-Bridging-Header.h
│   ├── ShaderTypes.h
│   ├── Shaders.metal
│   ├── Base.lproj/
│   │   └── Main.storyboard
│   └── Info.plist
├── ARDepthDataExample.xcodeproj/
│   ├── .xcodesamplecode.plist
│   └── project.pbxproj
└── Configuration/
    └── SampleCode.xcconfig

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 5 project/configuration file(s) and 4 source declaration(s).

Overall architecture

flowchart LR
    N1["AppDelegate"]
    N2["ViewController"]
    N3["RenderDestinationProvider"]
    N4["ARKit APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4

Reference code

ARDepthDataExample/AppDelegate.swift:11 — architecture anchor

@UIApplicationMain
class AppDelegate: UIResponder, UIApplicationDelegate {
    // ...
}

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 ARKit.

Ownership and state

classDiagram
    Renderer *-- Int : kMaxBuffersInFlight
    Renderer *-- Array : kImagePlaneVertexData
    Renderer o-- ARSession : session
    Renderer o-- MTLDevice : device

Ownership evidence

ARDepthDataExample/Renderer.swift:22 — stored dependency or nearest verified ownership anchor

let kMaxBuffersInFlight: Int = 3

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.

Class and protocol design

ARDepthDataExample/Renderer.swift:14 — representative type boundary

protocol RenderDestinationProvider {
    var currentRenderPassDescriptor: MTLRenderPassDescriptor? { get }
    var currentDrawable: CAMetalDrawable? { get }
    var colorPixelFormat: MTLPixelFormat { get set }
    var sampleCount: Int { get set }
}

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

Access control

Reference code

ARDepthDataExample/Renderer.swift:226 — representative boundary

    fileprivate func setMTLPixelFormat(_ texturePixelFormat: inout MTLPixelFormat?, basedOn pixelBuffer: CVPixelBuffer!) {
        // ...
    }

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; Provider: RenderDestinationProvider; Renderer: Renderer.
• Protocols: RenderDestinationProvider.
• Methods: drawRectResized, update, loadMetal, updateAppState, updateCameraImageTextures, setMTLPixelFormat, updateARDepthTexures, createTexture.
• Files: ARDepthDataExample/Renderer.swift, ARDepthDataExample/AppDelegate.swift, ARDepthDataExample/ViewController.swift.

Architecture takeaways

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