Unfortunately I could not determine the issue with the screenshots you provided - a scene would be better
How can I provide you with the scene?
You can first minimize your scene then upload it somewhere and DM me the link.
I will do that in a minute, thank you!
UE 5.7: I added multiple stationary Rect Lights in the level. After lighting baking, inconsistent brightness seams appear between two adjacent mesh polygons lit by the real-time component of stationary lights. The seams under static lights and movable lights render correctly without this issue.
I created a blank project and set up a simple scene. I uploaded a demo project zip that has already been bulit lightmass. Thanks a lot!
StationaryLightSeam.zip (10.3 MB)
The issue is no longer reproducible in 5.8 (the commit is 5.7.4 compatible): https://github.com/AlanIWBFT/UnrealEngine/commit/72e0effe9c10497f4881951c56ca6036082d3291
You can merge all changes up to https://github.com/AlanIWBFT/UnrealEngine/commit/dde97f775ea23e83a39c53bf97d5d15306d1a092 into your 5.7.4 branch
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Hi! Any reason for moving to an .exe file? I’m cool with it, but the guy I’m working with is not very trusting of random executables, so I’d prefer the archive patch format. It also allows me to distribute it along with my custom shader patch much easier without having to get a clean engine install for the patch (the installer detected that I had a GPULM file modified, so I had to get a clean egine install to install the patch, then reapply my shader patch)
I do seem to have problems with the baked lights, as if they’re baked without the patch on 5.8.2 (installed on a clean engine install with the .exe)
I am working on cross-platform development. Using the branch you provided, I successfully fixed the stationary lightmap seam issue. The preview works correctly for PC in the editor. However, a new problem appears when switching to Android preview within the editor: thin geometry at wall corners receives light reflections originating from outside the wall (light leakage). This leakage was not present before.
It’s because I’ve started modifying engine runtime files and an archive including all the files touched is prohibitively large (for example, the archive for 5.8.2 is ~349 MiB. it may work for a few versions, but definitely won’t work as I need to host multiple verions). You can generate the set of patched files by
- Launch the installer then goto your TEMP/is-XXXXXX.tmp and get the
Patch.hdf - Use
hpatchzto generate the set of patched files using a clean engine install and the hdf. You can lookup thehpatchzhelp about how to do that or ask your AI agent to help you.
Oh, that makes a lot of sense! Thank you very much on the patch thing! <3
Any idea on why the baking issue on the screenshot above?
That’s on a completely clean engine build with just the patch installed
Not to be unhelpful with minimal provided info, I’m just not sure what to say other than it’s a Forward Shading project and the lighting setup is one static directional light
Edit: Oh my god, I’m sorry… Guy just really loves using BSP brushes with dead UVs 
Had to yell at him for it lol
Edit2: Turns out it’s a VR Expansion Plugin thing where the motion controller map is using meshified BSP, so I yelled at him for nothing
He deserves it anyway
5.8.3 support?
Yeah, I accidentally updated my launcher version to 5.8.3 and had to download the source build
I’m sure Yujiang’s gonna get to it eventually
If you’re using movable lighting (if an object is set to movable or uses the volumetric lightmap), mobile samples those differently from Desktop.
Desktop will sample a volumetric texture, which will basically grab the 8 nearest light probes and blend between them across the object’s surface, whereas mobile will use cached lightmaps, which is doing the same thing, but just for the object’s origin point. That might be causing the leaking
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Release 5.8.3 2026.09.24
https://downloads.luoshuangfw.io/gpulm-releases/GPULM-5.8.3.exe
Back to release list
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Hi, I’m encountering an issue where lightmap UVs look broken in the packaged Android build on some meshes.
I’m using commit 387ca76 on top of Meta’s UE 5.7.4 fork.
In the editor’s Android Preview, everything looks completely correct. Also, meshes with Generate Lightmap UVs turned off do not have this issue. My guess is that during cooking, meshes are being rebuilt with a different lightmap UV algorithm/padding.
Send me a repro/minimized version of your scene for me to investigate
Here it is. I have included the UE project, packaged APK for Meta Quest, and Saved/Cooked folder.
Huge thanks for all the effort you keep putting into this plugin for the community!
I could not reproduce your issue 1 with 5.8.3:
That’s strange. However, I can actually see 4 spots with black artifacts on your screenshot, which could be related to the same bug.
I also just tested this on a clean UE 5.7.4 from the Epic Launcher with your patch on top. I packaged it for Windows, and the exact same issue persists.
I have uploaded the Windows build to the same Google Drive folder.