Metal Renderer

A real-time physically-based render engine built with Metal and Swift.

• OBJ Loader - Import 3D models in OBJ format
• Instanced Rendering - Efficient GPU-driven instance rendering
• Dual Shading Models
  • Blinn-Phong shading for traditional lighting
  • Physically-Based Rendering (PBR) with metallic-roughness workflow
• Shadow Mapping - Point light omnidirectional shadows using cube map arrays with PCF filtering

• Scene Graph - N-ary tree structure for hierarchical transforms
• Scene Persistence - Save and load scenes to/from disk in JSON format
• Asset Management - Centralized asset loading and caching

• ImGui Integration - Interactive editor layer for scene manipulation
• Real-time Controls - Adjust materials, lights, and transforms in real-time

The PBR implementation follows industry-standard techniques for realistic material rendering:

Uses the Disney Diffuse Model from Burley 2012:

• More physically accurate than Lambertian diffuse

Implements the Cook-Torrance microfacet model (Cook & Torrance 1982):

• Normal Distribution Function (NDF): GGX/Trowbridge-Reitz for realistic highlights
• Geometry Function: Smith's separable masking-shadowing function
• Fresnel: Schlick approximation for angle-dependent reflectance

Environment-based lighting using prefiltered cube map arrays:

• Split-sum approximation following Epic's 2013 approach
• Prefiltered environment maps - Multiple roughness levels stored in cube texture arrays
• BRDF Integration LUT - Precomputed environment BRDF for real-time performance
• Diffuse and Specular IBL - Separate contributions for accurate material response

Point lights use omnidirectional shadow mapping:

• Cube map array storage (one cube per light)
• Percentage-Closer Filtering (PCF) for soft shadow edges
• Poisson disk sampling for better quality

• Distance-based depth testing in world space

Scenes are serialized to JSON with a hierarchical structure:

{
  "rootNode": {
    "assetId": "root",
    "id": "E746668A-A378-4042-833C-FDF1852C7747",
    "nodeType": -1,
    "transform": {
      "position": [0, 0, 0],
      "scale": [1, 1, 1]
    },
    "children": [
      {
        "id": "A5069381-FEAF-4191-B1B6-9069FDD2CE4B",
        "assetId": "e3dd97f8f84d2a54a95aac60bde6e2274cf39fe3073c15fd8c309dc1aa73d978",
        "nodeType": 0,
        "transform": {
          "position": [-0.8385614, 1.1081522, -2.5150156],
          "scale": [1, 1, 1]
        },
        "children": []
      }
    ]
  }
}

Each node includes:

• Unique identifier (UUID)
• Asset reference (SHA-256 hash)
• Transform data (position, rotation, scale)
• Children array for hierarchy

• Metal - Apple's low-level graphics API
• MetalKit - Texture loading and view management
• Metal Performance Shaders - GPU-accelerated image processing

• Forward rendering pipeline - Single-pass rendering with multiple materials
• Cube texture arrays - Efficient storage for environment maps and shadow maps
• GPU-driven rendering - Minimize CPU overhead with instancing

1. Open the .xcodeproj file in Xcode
2. Build and run (⌘R)

Requires:

• Xcode 14.0+
• macOS 12.0+ deployment target
• Metal-capable Mac

• Disney BRDF Paper (2012)
• Cook-Torrance Reflectance Model (1982)
• Real Shading in Unreal Engine 4 (2013)