: Press the Home key while in-game to open the ReShade menu and enable the shader. How install RTGI/ReShade (2021) GTA 5 MODS
There is no legal free download of RTGI 0.51. Support the developer if you want the software — it's reasonably priced for what it does. rtgi 0.51 download free
If you're looking for technical details about RTGI 0.51's algorithm (e.g., hierarchical temporal accumulation, ray marching in screen space), I can explain that without advocating piracy. Just let me know. : Press the Home key while in-game to
[Game Render Pipeline] ---> [Depth Buffer Extraction] ---> [RTGI Shader Pass] ---> [Final Screen Output] hierarchical temporal accumulation