Concerns Regarding the Phasing Out of Raytracing in Favor of Lumen in Future Unreal 5.4+

Hello, we are having the same issues, unable to even get close quality. It is flickering heavily. We have emissive lights and a mirror hallway. The scene looks awesome in 5, but forcing Lumen gives us extreme flickering and noticeably lower quality. We tried all Project Settings and console commands.

Please repreceate this or adjust the quality of Lumen to give the exact same results!

Is there no better way for your team to keep already robust features for users? Sometimes the quality and ease of features decreases a lot in one update. For instance with displacement or the SteamVR Plugin. I understand maybe for development it makes sense, but it is a real pain.


As i commented in this post PLEASE ! - Don't remove Raytracing Reflection (Deprecated) in 5.4 - #15 by RenyV
the combination of these 2 variables makes reflections a lot better when roughness is 0
r.Lumen.Reflections.DownsampleFactor 0
r.Lumen.Reflections.Temporal 0
but that it introduces a lot of noise if roughness isn’t 0. for those
r.Lumen.Reflections.Temporal has to be set to 1 to look better
so, it’s a trade off if you have different roughness in the scene. at least for realtime and interactive solutions.
renders can be improved with more samples and a good post denoiser

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Feeling you! I was a bit gutted to find it missing after already putting a lot of work into a new project in 5.4. At first I thought that Lumen has probably gotten good enough now that it doesn’t matter but now I’m having issues getting good reflections in scenes.

A lot of the time I’m getting black areas where nothing is reflected, I’ve seen people say this is down to those materials or meshes not contributing to global illumination but I’ve found little info as to why.

Some of the scenes I’m working on for the project are on a huge scale i.e. planets in space. The camera may be very far from the world origin, in this circumstance the lumen reflections are so bad that it’s not even workable, like they go really blocky. I tried in 5.3 a similar scenario with ray traced reflections and they were fine. If anyone knows how to fix this then please tell. I’ve done things like increase the quality settings in the post process volume, change it to hit lighting for reflections and play with the skylight capture settings… i.e. increase resolution but nothing changed. The only thing that looked good was path tracing, but in some circumstances that creates its own issues, like materials not rendering at all, no WPO displacement, no volumetrics and huge rendering times.

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