I was waiting for you saying something official about this!
Thank you again for your huge contributions @yujiang.wang !! You deserve the very best 
Would this work with 5.5.3 and 5.5.4 ?
The answer is we don’t know until you tried
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Hi @yujiang.wang ,
Welcome back. I have always personally wanted to thank you for the way you wrote the CUDA code and for sensing the number of CUDA cores available.
The 5.5 version will NOT work for the same reasons there was never an LGPU 5.5 or LGPU 5.2
The 5.5 source code is a mess.
In 5.6 There has been a lot of cleaning up code.
IMHO there is little point if you compare the 5.5 and 5.6 repositories there are > 2000 fixes/patches.
My work in integrating LGPU into 5.6, Radiosity is working already, and has been significantly easier compared to 5.5, which was abandoned.
Off-topic
My attempt to fix GTX Pathfinding 5.5 finally worked after 27 hours of dev and this needed a fresh project as the 5.4 project convertor is broken in 5.5, just like 5.2
5.6 seems to convert a project from 4.27 to 5.5 without any problems
You would be wasting valuable time. Look at the hours spent backwards converting that fix to landscape to the prior version, just one patch.
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Thanks for your work!
One issue that some of us noticed with GPU Lightmass is that since UE5.5 stationary lights do not work properly with GPU lightmass.
You can test this by disabling Virtual Shadow Maps and if you try to bake them they will produce not direct light.
Will download this to confirm if this still happens in this case.
Thanks again!
Thanks for you work! 
Great news!! Very much appreciated you’re continuing working on this great plugin!
This ? Unreal Engine Issues and Bug Tracker (UE-291212)
If so, Epic isn’t going to fix it sadly 
I appreciate the original poster updating it, but what is the actual future of the feature in Unreal Engine?
If it is not deprecated officially then it will need support officially, so which one will it be?
Hi @Robert.Cummings ,
The Legal status is given below
Legal Status
There is NO BINARY because it’s NOT an Epic official version. Users who are Market Creators have asked to go to 5.4 for performance reasons on Nvidia GTX VRAM being better
This version is all the patches and files to build “Luoshuangs GPULightmass”. LGPU Lightmass patches from the commit GPULightmass5-0-0-cherry-pick repository and others have been added
Use of this repository is without warranty and no responsibility for the use and any subsequent problems are accepted This is for research, development, and training quality, not professional quality. Like other functions, it has an Experimental Status.
This means that, under the Epic EULA, you cannot place anything Experimental into professional code. See Epic’s official statement
Publishing Limitations:
When a feature is experimental, users/players may not be able to publish applications with it or the feature may have limitations while in the experimental state.
No Backward Compatibility Guarantees: Epic Games does not guarantee backward compatibility for assets created while a feature is experimental, and the APIs for these features are subject to change
End of Legal Status for Epic GPU Lightmass and Luoshuangs-GPULightmass-5.6-preview Started 10th May 2025
This application is used to generate visualisations of a professional standard.
This does not need the programs to be official Epic code.
If you need more official information consult the Unreal Engine Fornite (UEFN)Terms and Conditions they are the same as the Standard Engine T & C
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Very good question (will it be deprecated at some point?!)
Maybe @yujiang.wang could make this a commercial plug-in? That way his efforts could be honoured with money as well
There ya go, in case people need it and don’t want to fiddle with git 
gpulm-5.6.patch (359.7 KB)
I tried applying patch to 5.5.3 (Meta’s fork) and of course it wouldn’t apply
List of conflicting files:
meta553_vs_GPULM560.txt (4.3 KB)
There are probably a way to many differences between 5.5 and 5.6 on rendering side, even just for GPULM.
Just to be sure - is there any chance a project can’t be opened in the future again with a ‘clean’ launcher Unreal build when using your fixed & improved GPUlm? I’m testing it in 5.6 now and the first time when doing a new light build, I get some messages. See below.
- Some meshes are not using the latest lightmap UV generation algorithm etc
- the following levels used as level instances contain invalid lighting GUIDs … would you like them fixed?
- The levels are fixed now. However you need to reopen your main level for the fix to take effect.
edit: spelling
- and 3. are compatible changes. 1. however, isn’t. You’ll still be able to open it in vanilla UE5.6, the lightmap UVs will however be generated using the latest one coming with 5.6 though. The lightmaps will come broken, yet can be fixed with one lighting build.
Also, if you’re not using any Level Instances but get 2 and 3 right after 1, please redownload the patch as I fixed an issue which is a conflict between them.
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I get a crash immediately when trying to do your GPUlightmass in one project: Assertion failed: IsValid() [File:E:\UE5\Engine\Plugins\Experimental\GPULightmass\Source\GPULightmass\Private\EntityArray.h] [Line: 203]
Strange thing is: I don’t have an E drive. If I look in the default UE dir and that file, line 203 is part of a method(?) called ‘int32 GetElementIdChecked’. Any suggestion what I should be looking for that can cause this crash?
Edit: in another project I dont get a crash so I guess its something ‘strange’ in my project
I probably need your project to diagnose this crash. It is a rare one among GPULM crashes. The E:\UE5 path is where the engine is compiled, which matches my computer.
I’m testing atm. I think its foliage related. Will come back to this and/or create a small project for you to test.
Edit: this project crashes with the message from two post above if a particular Quixel Megascan asset is in the scene. Its the SM_CommonHazel_Forest_02 from the CommonHazel pack. It crashes when its on a streaming level as well as if its on the persistent level.
Try to clean and isolate the problem and send the project to Luos, just with the very needed assets.
@miguel1900 You’re right, just did.
Edit: and Yujiang Wang has fixed that crash already. Download file from his post has been updated.
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