Square artifacts after baked lighting UE5.1 GPUlightmass

Hello,
I need a help with this weird squared artefacts I have after baking lighting with GPU lightmass in UE5.1.
After many tries I found that this is cause of Irradiance cache in lightmass settings. If its turned off, there is no artefact (but almost no indirect lighting). If I turn it on, there is plenty of these artefacts.
If I am baking in interactive mode, all lightmaps are perfectly smooth. But if I am baking all scene, I have artefacts.
Can anybody help me with it? I never have this problem in previous versions of UE.
Thank you for any tips




I’m not sure but my first thought would be to check the lightmap resolution or lightmap id. How does it look in lighting only or detail lighting mode?

Lightmap resolution is 1024 or 2048 and lightmaps are fine without any overlaping faces as these walls are pretty simple. Like simple rect. All wall meshes are only faces without any thickness. Problem occures only with Irradiance cache enabled in GPU Lightmass.
I started to build this project in UE5.0.3 and then move to 5.1 where I did a lot of changes. In older version baking is without any issue. Only here in 5.1 this problem occures. It looks like I will have to go back and add all changes to older version as in 5.1 baking is screwed

[outdated, driver version 528.49 appears to work fine] Hi, I recently solved all of my GPU lightmass baking artifacts in UE 5.1 by downgrading my Nvidia driver to version 522.25 after reading Luoshuang’s post on the Epic’s GPUlightmass - Development thread on these forums.

This problem persists even up to driver version 528.02 which I recently tested. Luckily reverting to the aforementioned version solved all of my issues. This is a MAJOR problem that surely affects a lot of people and yet I saw Luoshuang’s post almost by accident after spending a LOT of time investigating this issue.

PS: Just above that post he has another describing how to fix a line of erroneous code by simply editing one of the files, here’s the link to that. - I’m not sure if me doing this played a role in solving my problems, I tried it first and it didn’t fix my issue but after reverting my driver boom everything was perfect.

wow thank you. I am working on another project in 5.1 and I will have to bake the scene. I want to try edit LightmapRenderer.cpp. I bought newest 4090 so I don’t know if I can simply return to older drivers. But I will try if this method will not help.

Fortunately 522.25 was the launch Driver for the 4090 so you should be able to use it without issue, if I discover newer driver versions working I’ll be sure to come back and update my post(s).

EDIT: - 531.18 seems to be the latest fix, so we can finally upgrade.

I will keep my posts updated.

The Creator of GPU Lightmass (Luoshuang) just posted that he tested Nvidia driver version 531.18 and that it appears to be working as intended according to his tests.

Here is his post Epic's GPUlightmass - #447 by Luoshuang

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