I understand you're looking for information about RTGI (Realtime Global Illumination), likely referring to the shader by Pascal "Marty McFly" Gilcher, version 0.51.
However, I must clarify: for legitimate use. It is a paid product available on Patreon (Marty McFly's page) for supporters. Version 0.51 is an older release, but still under the same licensing. rtgi 0.51 download free
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. I understand you're looking for information about RTGI