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Metal Primitives in Swift and Objective-C

This project demonstrates the basic primitives of the Metal framework by Apple, showcasing how to render various graphics using Metal in both Swift and Objective-C. It serves as an educational resource for developers interested in graphics programming on iOS and macOS platforms.

Overview

The project covers a range of rendering examples:

  • Clear Screen: Basics of setting up a Metal view and clearing the screen with a solid color.
  • Draw 2D Triangle: Rendering a simple 2D triangle on the screen.
  • Draw Spinning 3D Cube: Displaying a rotating 3D cube with basic transformations.
  • Draw Spinning Teapot with Manual Lighting: Rendering a spinning teapot model with custom lighting effects.
  • Draw Spinning Cow with Manual Lighting and Custom Texture: Displaying a textured cow model with lighting.

Each example is fully programmatic—no Storyboards, XIBs, or NIBs are used—providing a clear understanding of the code involved in setting up and rendering Metal views.

Demo

Here is the previews of multiple metal screens rendering on an iOS simulator:

Demo-on-iOS-devices

Here is the previews of multiple metal screens rendering on a macOS simulator:

Demo-on-macOS-devices

Motivation

This project is a migration and enhancement of the code from Warren Moore's book, Metal by Example, originally written in 2015. By updating the code to support the latest versions of Swift and Objective-C, and integrating it with both iOS and macOS platforms, we aim to make Metal's functionalities more accessible to modern developers.

The project also incorporates cross-platform support from dehesa/sample-metal, allowing the examples to run seamlessly on different operating systems and frameworks. By connecting all the code into a single app, we've streamlined the learning experience.

Features

  • Cross-Platform Rendering: Examples run on both iOS devices and macOS systems.
  • Swift and Objective-C: Implementations in both languages to cater to a wider range of developers.
  • Mermaid Diagrams: Each Metal view includes Mermaid diagrams explaining code functionalities and the relationships among code blocks.
  • 100% Programmatic UI: No Interface Builder files; all views are created via code for better transparency.
  • Educational Focus: Code is well-documented and structured to facilitate learning.

Code Structure

High-Level Architecture Diagram

This diagram provides an overview of the entire app's architecture, highlighting the conditional compilation for iOS and macOS platforms and how different views are integrated.

graph TD
    %% Define styles
    classDef iOS fill:#43F6,stroke:#4285F4
    classDef macOS fill:#F4F6,stroke:#34A853

    %% App Structure
    A["MetalPrimitivesApp<br>@main App"]
    A -->|contains| B[WindowGroup]

    %% Platform Conditional Views
    B -->|Platform: iOS| C[iOS Views]
    B -->|Platform: macOS| D[macOS Views]

    %% iOS Views
    subgraph iOS Views
        direction TB
        C1[ObjCMetalPlainViewControllerRepresentable]:::iOS
        C2[MetalTexturingViewRepresentable]:::iOS
        C3[MetalLightingViewRepresentable]:::iOS
        C4[Metal3DViewRepresentable]:::iOS
        C5[Metal2DViewRepresentable]:::iOS
        C6[MetalPlainViewRepresentable]:::iOS
        C7[iOS_ViewControllerRepresentable]:::iOS
        C8[iOS_SwiftUI_RootContentView]:::iOS
    end
    C --> C1 & C2 & C3 & C4 & C5 & C6 & C7 & C8

    %% macOS Views
    subgraph macOS Views
        direction TB
        D1[MetalTexturingViewRepresentable]:::macOS
        D2[MetalLightingViewRepresentable]:::macOS
        D3[Metal3DViewRepresentable]:::macOS
        D4[NSMetal2DViewRepresentable]:::macOS
        D5[NSMetalPlainViewRepresentable]:::macOS
    end
    D --> D1 & D2 & D3 & D4 & D5
Loading

Explanation:

  • The MetalPrimitivesApp uses a WindowGroup to host the main content.
  • Based on the platform (iOS or macOS), it conditionally includes different views.
  • The iOS Views and macOS Views are grouped under their respective platforms.
  • Each platform includes a set of representable views that integrate Metal rendering into SwiftUI.

App Structure Overview

This class diagram illustrates the overall structure of the app, focusing on the relationships between the main app entry point, SwiftUI views, and UIKit/AppKit view controllers.

classDiagram
    %% Main App Entry Point
    class MetalPrimitivesApp {
        +var body: some Scene
    }
    MetalPrimitivesApp --> WindowGroup

    %% SwiftUI Views
    WindowGroup --> iOS_SwiftUI_RootContentView
    iOS_SwiftUI_RootContentView --> ObjCMetalPlainViewControllerRepresentable

    %% UIViewControllerRepresentable Wrapper
    class ObjCMetalPlainViewControllerRepresentable {
        +makeUIViewController()
        +updateUIViewController()
    }
    ObjCMetalPlainViewControllerRepresentable ..|> UIViewControllerRepresentable

    %% UIKit View Controllers
    ObjCMetalPlainViewControllerRepresentable --> ObjCMetalPlainViewController

    %% Typealiases and Base Classes
    class MySwiftViewController
    MySwiftViewController <|-- UIViewController
    MySwiftViewController <|-- NSViewController
    ObjCMetalPlainViewController <|-- MySwiftViewController
Loading

Explanation:

  • MetalPrimitivesApp is the main entry point of the app, containing the WindowGroup.
  • iOS_SwiftUI_RootContentView is the main SwiftUI view for iOS, which uses ObjCMetalPlainViewControllerRepresentable to bridge UIKit components.
  • ObjCMetalPlainViewControllerRepresentable conforms to UIViewControllerRepresentable to integrate a UIKit view controller within SwiftUI.
  • ObjCMetalPlainViewController is an Objective-C view controller that handles Metal rendering.

For more details and illustrations, please check out Documentation.md.

Getting Started

Prerequisites

  • Xcode 13 or later (supports both Swift and Objective-C)
  • iOS 13 or later / macOS 10.15 or later
  • Swift 5 or later

Installation

  1. Clone the Repository:

    git clone https://github.com/CongLeSolutionX/Metal-Primitives.git

  2. Open the Project in Xcode:

    cd Metal-Primitives
open MetalPrimitives.xcodeproj

  3. Select the Target:

    • Choose either the iOS or macOS target depending on your development environment.

  4. Build and Run:

    • Press Cmd + R to build and run the project on your device or simulator.

Understanding the Code

Programmatic Views

All views in this project are created programmatically. This approach provides:

  • Full Transparency: Understanding exactly how views are initialized and managed.
  • Flexibility: Easier to manipulate views dynamically.
  • No Storyboard Constraints: Avoids issues related to storyboard merges in collaborative environments.

Mermaid Diagrams

To help visualize the architecture and flow of each example, we've included Mermaid diagrams in the documentation of each module.

Example: Metal Views and Renderers Class Diagram

This diagram shows the relationship between the Metal views and their respective renderers.

classDiagram
    %% SwiftUI Representable Views
    class Metal3DViewRepresentable {
        +makeUIView()
        +updateUIView()
        +makeCoordinator()
    }
    class MetalLightingViewRepresentable {
        +makeUIView()
        +updateUIView()
        +makeCoordinator()
    }
    class MetalTexturingViewRepresentable {
        +makeUIView()
        +updateUIView()
        +makeCoordinator()
    }

    Metal3DViewRepresentable ..|> UIViewRepresentable
    MetalLightingViewRepresentable ..|> UIViewRepresentable
    MetalTexturingViewRepresentable ..|> UIViewRepresentable

    %% Underlying Metal Views
    class CAMetal3DView {
        +device: MTLDevice
        +renderer: RendererFor3DView
    }
    class MTKView

    Metal3DViewRepresentable --> CAMetal3DView
    MetalLightingViewRepresentable --> MTKView
    MetalTexturingViewRepresentable --> MTKView

    %% Coordinators (Renderers)
    Metal3DViewRepresentable --> CubeRenderer : makeCoordinator()
    MetalLightingViewRepresentable --> TeapotRenderer : makeCoordinator()
    MetalTexturingViewRepresentable --> CowRenderer : makeCoordinator()

    %% Renderers
    class RendererFor3DView {
        <<Protocol>>
        + device: MTLDevice
        + draw(layer: CAMetalLayer, time: (now: Double, display: Double))
    }
    RendererFor3DView <|.. CubeRenderer
    RendererFor3DView <|.. TeapotRenderer
    RendererFor3DView <|.. CowRenderer

    CubeRenderer ..|> RendererFor3DView
    TeapotRenderer ..|> MTKViewDelegate
    CowRenderer ..|> MTKViewDelegate
Loading

Explanation:

  • Each representable view conforms to UIViewRepresentable and integrates a Metal view into SwiftUI.
  • Metal3DViewRepresentable uses CAMetal3DView, which utilizes a custom renderer (CubeRenderer).
  • MetalLightingViewRepresentable and MetalTexturingViewRepresentable use MTKView and custom renderers (TeapotRenderer and CowRenderer respectively).
  • Renderers conform to either RendererFor3DView protocol or MTKViewDelegate.

Learning Objectives

By exploring this project, you will:

  • Understand Metal Basics: Learn how to set up a Metal environment and render basic shapes.
  • Work with Shaders: Write and modify vertex and fragment shaders for custom rendering effects.
  • Implement Transformations: Apply translations, rotations, and scaling to 3D objects.
  • Apply Lighting Models: Understand how lighting affects rendering and how to implement it manually.
  • Work with Textures: Load and apply textures to 3D models for more realistic effects.
  • Develop Cross-Platform Code: Write code that runs on both iOS and macOS platforms.

Resources and References

Contributing

We welcome contributions! If you'd like to improve the project, please:

  1. Fork the Repository: Create your own fork on GitHub.

  2. Create a Feature Branch:

    git checkout -b feature/YourFeature

  3. Commit Your Changes:

    git commit -m 'Add your feature'

  4. Push to the Branch:

    git push origin feature/YourFeature

  5. Open a Pull Request: Submit your changes for review.

License

This project is licensed under the MIT License. See the LICENSE file for details.