Truly astonishing how much generalized modding seems to be possible through general DirectX (8/9) interfaces and official Nvidia provided tooling.
As an AMD graphics card user, it’s very unfortunate that RTX/this functionality is proprietary/exclusive Nvidia. The tooling at least. The produced results supposedly should work on other graphics cards too (I didn’t find official/upstream docs about it).
For more technical details of how it works, see the GameWorks wiki:
While this functionality is proprietary to Nvidia ray tracing isn’t and since RTX is just nvidia’s brand of ray tracing your statement of RTX being proprietary isn’t wholly accurate.