A ray tracing program

This project is a ray tracing demonstration written in C++. A 3D environment is virtualized and rendered, and the result is displayed in a window using the SDL development library.

Click here for a slideshow of development screenshots.

Features

3D visuals

• Sphere subjects
  • with matte finish
  • with mirror finish
  • made of glass (TODO)
• Lighting
  • Diffuse
  • Specular
• Shadows
• Reflections
• Refractions (TODO)

CPU-only

As an exercise, all graphics computations (aside from SDL rendering) are run on the CPU instead of the GPU. No external graphics libraries are used.

Although efforts have been made to improve performance, it is a secondary priority of this exercise. We have already excluded the benefits of hardware acceleration. The main goal here is to provide a simple demonstration of how ray tracing actually works.

Click here to view the the start of the code for the graphics computation logic. Scene::write_frame() generates a camera ray for each pixel in the display, and cast() follows, or "traces", each ray in order to compute the color of its corresponding pixel.

OpenMP is leveraged to parallelize the ray casting.

FPS counter

A frame per second count is written to the terminal screen in real time using the ncurses library. Checking this value is the simplest way to estimate performance. Observed values may vary across different runtime machines/environments.

Run it yourself

Note: This project was developed in WSL (Windows Subsystem for Linux) Version 2. WSL users must make sure their own version of WSL is new enough to support WSLg, which makes it possible for a SDL window to launch from within WSL.

1. Install dependencies

   On Debian systems

   sudo apt update
   sudo apt install build-essential cmake libncurses-dev libsdl2-dev

2. Download

   git clone https://github.com/terranchao/raytracer.git

3. Build

   CMake (GCC) is used to build this project.

   cd raytracer
   cmake -B build
   cmake --build build

4. Run

   ./build/raytracer
   

   For WSL users: There is a known WSLg-SDL compatibility issue that causes a segmentation fault. If a segmentation fault occurs, try running the following and retrying. This must be done once per shell instance.

   $ export LIBGL_ALWAYS_SOFTWARE=1

References

Thank you to these pages for the inspiration.

• https://github.com/ssloy/tinyraytracer/wiki/Part-1:-understandable-raytracing
• https://www.scratchapixel.com/lessons/3d-basic-rendering/minimal-ray-tracer-rendering-simple-shapes/ray-sphere-intersection.html
• https://www.scratchapixel.com/lessons/3d-basic-rendering/ray-tracing-generating-camera-rays/generating-camera-rays.html
• https://en.wikipedia.org/wiki/Phong_reflection_model