Modern rendering with Metal

At a glance

Project structure

Source bundle/
├── Application/
│   ├── main.m
│   ├── AAPLAppDelegate.h
│   ├── AAPLSettingsTableViewController.mm
│   └── AAPLViewController.h
├── Asset/
│   └── AAPLTextureManager.mm
└── Renderer/
    ├── Shaders/
    │   ├── AAPLMeshRenderer.metal
    │   └── AAPLShaderCommon.h
    ├── AAPLMesh.h
    ├── AAPLRenderer.h
    ├── AAPLRenderer.mm
    ├── AAPLScene.h
    └── RenderTech/
        └── AAPLMeshRenderer.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, Objective-C, Objective-C++.
• The verified tree contains 7 project/configuration file(s) and 83 source declaration(s).

Overall architecture

flowchart LR
    N1["main"]
    N2["AAPLCameraController"]
    N3["AAPLTextureManager"]
    N4["AAPLMeshRenderer"]
    N5["Metal APIs"]
    N1 --> N2
    N2 --> N3
    N3 --> N4
    N4 --> N5

Reference code

Application/main.m:9 — architecture anchor

int main(int argc, char * argv[])
{
    // ...
        return UIApplicationMain(argc, argv, nil, NSStringFromClass([AAPLAppDelegate class]));
    // ...
}

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
    AAPLMaterial o-- id : vertices
    AAPLMaterial o-- id : normals
    AAPLMaterial o-- id : tangents
    AAPLMaterial o-- id : uvs

Ownership evidence

Renderer/AAPLMesh.h:27 — stored dependency or nearest verified ownership anchor

@interface AAPLMesh : NSObject <NSCopying>
// ...
@property (nonatomic, readonly) id<MTLBuffer> vertices;
// ...
@end

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

Renderer/AAPLMesh.h:18 — representative type boundary

@protocol MTLTexture;

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

Access control

Reference code

Application/AAPLInput.h:65 — representative boundary

@interface AAPLTouch : NSObject
// ...
    @property simd::float2 pos;         // Current position.
// ...
@end

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

Main application flow

sequenceDiagram
    participant AAPLRenderer
    participant _commandQueue
    participant MTLRenderPassDescriptor
    participant AAPLCamera
    participant spotCamera
    participant commandBuffer
    participant NSString
    participant _device
    AAPLRenderer->>_commandQueue: commandBuffer()
    AAPLRenderer->>MTLRenderPassDescriptor: renderPassDescriptor()
    AAPLRenderer->>AAPLCamera: initPerspectiveWithPosition()
    AAPLRenderer->>spotCamera: updateState()
    AAPLRenderer->>commandBuffer: renderCommandEncoderWithDescriptor()
    AAPLRenderer->>NSString: stringWithFormat()
    AAPLRenderer->>_device: newBufferWithLength()
    AAPLRenderer->>commandBuffer: commit()

Reference code

Renderer/AAPLRenderer.mm:1812 — generateSpotShadowMaps()

#if USE_SPOT_LIGHT_SHADOWS
    // ...
    [commandBuffer commit];
#endif

Naming conventions

• Types: Controller: AAPLCameraController, AAPLSettingsTableViewController, AAPLViewController; Delegate: AAPLAppDelegate, WindowSceneDelegate; Manager: AAPLTextureManager; Renderer: AAPLMeshRenderer, AAPLRenderer; Scene: AAPLScene; View: AAPLView.
• Protocols: MTLTexture, MTLBuffer, MTLDevice, MTLHeap, MTLDevice, MTLBuffer, MTLDevice, MTLRenderCommandEncoder.
• Methods: initWithDevice, update, getTexture, addTextures, request, setRequiredMip, loadMipsToTexture, addMips.
• Files: Asset/AAPLTextureManager.mm, Application/AAPLAppDelegate.h, Application/AAPLSettingsTableViewController.mm, Application/AAPLViewController.h, Renderer/AAPLMesh.h, Renderer/AAPLRenderer.h.

Architecture takeaways

• main is the main source-visible entry or composition anchor for this sample.
• Framework work reaches simd, Metal, vector, 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.
• The source does not justify labeling the design protocol-oriented.

Source map

• Official Apple documentation