Ray Tracing in C++ and Metal

This project implements a basic ray tracer in C++ and provides an optimized version using Metal for GPU acceleration on macOS. The ray tracer generates a 3D scene with spheres and light sources, rendering the output as a PPM image.

Features

• CPU Implementation: A basic ray tracer written in C++.
• GPU Optimization: A Metal-based implementation for faster rendering on macOS devices with Apple Silicon.
• Reflections and Transparency: Supports reflective and transparent surfaces.
• Lighting: Includes point light sources with shadow calculations.
• Scene Customization: Easily modify the scene by adding or removing spheres and lights.

File Structure

raytracer.cpp          # CPU-based ray tracer implementation
raytracergpu.mm        # GPU-optimized ray tracer using Metal
Raytracer.metal        # Metal shader for GPU ray tracing
compile.sh             # Script to compile the Metal-based implementation
untitled.ppm           # Output image (PPM format)
3.png           # High-resolution render with transparency 0.7
1.png      # First render
2.png    # Render with transparency 0.3

How It Works

CPU Implementation

The CPU-based ray tracer (raytracer.cpp) uses recursive ray tracing to compute:

• Ray-Sphere Intersections: Determines if a ray intersects a sphere.
• Lighting: Calculates the color of each pixel based on light sources and shadows.
• Reflections and Refractions: Handles reflective and transparent surfaces using recursive rays.

GPU Optimization

The GPU-optimized version (raytracergpu.mm and Raytracer.metal) leverages Metal's compute shaders to parallelize the rendering process. Each pixel is processed by a separate GPU thread, significantly improving performance.

How to Run

CPU Version

1. Compile the CPU version:

   c++ -std=c++14 -O3 -Wall raytracer.cpp -o raytracer

2. Run the program:

   ./raytracer

3. The output image will be saved as untitled.ppm.

GPU Version (macOS with Metal)

1. Navigate to the GPU Optimized directory:

   cd "GPU Optimized"

2. Make the compile script executable:

   chmod +x compile.sh

3. Compile and run the GPU version:

   ./compile.sh && ./raytracergpu

4. The output image will be saved as untitled.ppm.

Customizing the Scene

Adding Spheres

To add a sphere, modify the main function in raytracer.cpp or raytracergpu.mm:

spheres.push_back(Sphere(Vec3f(x, y, z), radius, surfaceColor, reflection, transparency, emissionColor));

• x, y, z: Position of the sphere
• radius: Radius of the sphere
• surfaceColor: RGB color of the sphere
• reflection: Reflectivity (0 to 1)
• transparency: Transparency (0 to 1)
• emissionColor: RGB color of emitted light

Adding Lights

To add a light source, use the same Sphere structure with emissionColor set to a non-zero value:

spheres.push_back(Sphere(Vec3f(x, y, z), radius, Vec3f(0, 0, 0), 0, 0, emissionColor));

Output

The rendered image is saved in PPM format. You can view it using any image viewer that supports PPM, such as Preview on macOS.

Example Renders

• High-resolution render with transparency 0.7:

• First render:

  

• Render with transparency 0.3:

Performance Comparison

Version	Resolution	Time
CPU	640x480	~10s
GPU	640x480	~1s

Requirements

• CPU Version: Any platform with a C++14 compiler
• GPU Version: macOS with Metal support (Apple Silicon recommended)

License

See LICENSE for license information.