Note regarding "Piece": If you are asking for a "piece" of code or a specific download link, I cannot provide direct download links for paid/patron software. However, v0.33 was widely circulated as a "public test" build at the time.

Unlike "native" ray tracing, which requires the computer to know about everything in a game world (even what's behind the character), Gilcher’s shader uses the "Depth Buffer"—the map of what is currently on your screen.

Unlike native ray tracing, which calculates light hitting objects across an entire virtual world, RTGI 0.33 uses and the game's depth buffer . It shoots virtual rays across the pixels currently visible on your screen to calculate how light bounces, scatters, and creates shadows.

As RTGI evolves, the 2021 "0.33" version represents a fascinating historical "freeze frame" of modding history.