Software Ray Tracer (Pixel Scratcher)

PixelScratcher is a real time software ray tracer written in C++ for Windows. Currently it implements ray tracing spheres, boxes and planes, with support for diffuse, specular, reflections, and refractions. The code can be found at https://github.com/Ihaa21/SoftwareRayTracer. Below I will detail the process of creating the raytracer.

I began the project during university after I saw lots of incredible research results on building real time raytracers, and I found tutorials at scratchapixel.com detailing how to implement the phong rendering equation. I tried my best to only use those tutorials as references and to code as much as I could on my own.

I used my code from Handmade Hero (a tutorial on making games from scratch), and I took out all the program specific code in it. I wanted to use the handmade hero code because it supported runtime compilation of code by swapping DLL's. Doing so, helped me test my project quicker since I could change my algorithms in code and recompile right away to see the changes in my app without having to close everything downand reopen.

After I had the app code setup, I initialize a buffer that stores the ray directions in camera space and I rendered it to the screen to see if the patterns looked correct.

Once I got the normals setup correctly, I derived a sphere/ray intersection formula and implemented it to render the spheres in my scene. Using that, I was able to draw my first sphere. I then began by visualizing the normals for the sphere, and checked to see if they where visually consistent.

Afterwards, I added my first lights into the scene. Since I didn't have a lighting model nor did the geometry have any color, I made every ray intersection shoot a shadow ray that would try to hit the light in my scene. If the shadow ray hit a light, it set the surface's value it came from, to the lights color. I then moved the light around to see if the bouncing code was working correctly. This can be seen below:

I turned to scratchapixel's tutorial on the diffuse + specular lighting model and implemented it for my spheres. Since I was already shooting shadow rays in the above example, adding a floor to the spheres generated shadows for me with the same implementation.

To capture indirect lighting, I added the ability for lights to bounce multiple times across the scene. I also added support for reflective materials for my geometry which better tested how well the indirect lighting was working.

Finally I finished the phong model by implementing refraction using a index that controls how bent the light ray becomes once it hits a surface. Calculating refraction was tricky because I had to be able to check if a ray is inside a sphere and when it hits the outside. I followed scratchapixels tutorial on the lighting model and fresnel equations to implement the desired refraction effect which can be seen below:

This program was my first attempt at building a ray tracer of any kind, and I learnt a lot about how the lighting model works as well as various issues that arise when attempting to implement indirect lighting. The code for this project can be found at https://github.com/Ihaa21/SoftwareRayTracer so feel free to check it out!