UE5 Light Material Flickering issue

Hi,
I’ve a problem on light material flickering problem on UE5.3 Preview 1. Kindly help to check what is the issue. Thanks!

Sample video is here:

Sample scene is here: Corona_Interior.7z - Google Drive

This is what happens when you try to light your scenes only with emissive surfaces. Use light actors (point/spot/rect)

Hi Arkiras, thanks for your replied. I’ve just inserted a point light with 1.0cd for testing. The problem still persisted.

You are probably going to have to lower the emissive intensity of your material or increase the brightness of your light. 1 candela is extremely dim…

You may not be able to get rid of it entirely as this is just the nature of having small bright emissives in your scene, not enough of Lumens rays will hit the emissive surface and so it will not converge to a stable result.

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Thanks Arkiras for your clear explanation with video demo about how emissive material works with lumens rays in UE5. Really appreciated!

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Hi Arkiras, I’ve tested to download the ArchVizInterior running on 5.2.1 & 5.3.0 P1. Both scenes turned out to have so much light flickering by its default level. Where on 5.0.3, everything looks fine. What is the explanation on this as the level is bright enough and there is no immersive light there as well. Can you help to explain on this? Thanks.


ArchVizInterior 5.2.1 & 5.3.0 Preview 1

ArchVizInterior 5.0.3

To be honest, that one looks like it might be noise from one of the old deprecated raytracing features, doesn’t really look like the noise I expect from Lumen.

You can try to narrow down the cause by turning Lumen off and seeing if it persists, then disabling any of the deprecated raytracing features you may have enabled in the post process.

If it is Lumen then you’ll want to look at the debug views:

Yeah, that’s crearly the deprecated ray tracing GI, which they have broken a lot in UE5 vs previous UE4 (and maybe UE 5.0, which is almost UE4)