It's using SerraEngine my custom simple game engine that I use to improve my skills in low-level programming.

Following the book RayTracing in one weekend as well as The Cherno's YouTube ray tracing series (superb, highly recommended!).

GitHub source (WIP)

Started just with a simple RGB screen:

First sphere (Hello, Japanese World!) (and transparent cube in the middle)

First sphere shading using the hit normal:

Applying light shading to the sphere:

Adding reflections:

From around 2fps on singlecore to 30fps on a Ryzen 9 5900X after multithreading and optimizations:

Path tracing with accumulation and debugging with Release mode instead of Debug: 350 FPS!

Adding a new sphere with different albedo to see the reflections, and cleant surface "acne"