Hello all,
I'm trying to create an accurate simulation of mirror reflections in UE5. I did some digging and determined that I need to focus on global (indirect) illumination Light Transport Algorithms, the first example of this that I found was path tracing, and I'm currently trying to modify my project to use it. From what I understand, path tracing is one way to implement global illumination, and UE5's Lumen GI uses a different algorithm.
I want to see the light spot produced by bouncing direct light off of a mirror, I learned that most game engine LTAs don't carry this functionality, as it is very computationally demanding. Meaning in order to get path tracing to work, I need to mess around with some settings.
In UE5 you can actually get a Path Tracing viewport mode, this mode gives me the effect that I want. In this image, the mirror itself is visible on the surface, but so is the light spot it makes, and they blend together slightly due to noise.
![](https://uploads.gamedev.net/forums/monthly_2022_10/4ce7435480c5408da6503a0bda77736c.DesiredPathTracing.jpg)
(Light spot is on upper right hand corner of the surface)
I've tried setting up a global PPV that only uses Path Tracing for its lighting and here's the result:
![](https://uploads.gamedev.net/forums/monthly_2022_10/9da9f5e4c80b45b2a7d65c586abdcbb9.PPVPathTracing.jpg)
(Mirror is reflected, but no light spot)
Here are my path tracing settings in the PPV, all forms of global illumination are turned off:
![](https://uploads.gamedev.net/forums/monthly_2022_10/688d0c7bc2b64723952b1d9f2272105f.PathTracingPPVSettings.jpg)
→ So really, I'm wondering what the difference is between my PPV configuration and what Unreal does when I enter path tracing view. I'm hoping to have the same effect occur in the regular lit view with my PPV as when I enter path tracing mode. Are there any noticeable discrepancies in my PPV settings, or things I'm not considering?
→ Notes: I have hardware raytracing and path tracing enabled in my project settings, I run this project on a 1660 Ti.
Thanks!