Got it, thanks. Probably is going to be hard isolating, I’ll try fixing myself firstly, if I fail, then I will try to figure out small repro project
don’t try to fix yourself as this should not happen in the first place - i.e. it should not be considered a user mistake
The problem is, my project is so huge, it might be faster this way rather then isolating 
From what I currently see, Static Bode Water Mesh component causes it, as it is stil experemental, probably has not much to do with gpulightmass itself, but I will continue investigating
Well, I am not sure. I just planted check:
if (!Instance.RenderData->RayTracingProxy ||
LODIndex >= Instance.RenderData->RayTracingProxy->LODs.Num())
{
….
continue;
}
in few places, and it worked. Somehow Water Component fails to build that stupid proxy, I could not find any way to force it do so
Is anyone else experiencing issues with GPULightmass and emissive materials?
Previously, emissive meshes contributed to the baked lighting automatically, but now the emissive lighting seems to be ignored.
Any idea if something changed recently?
Thanks!
I found the cause — I needed to enable the “Use Emissive for Static Lighting” checkbox.
It seems this wasn’t required in previous versions?
Release 5.6.1 2025.11.10
https://downloads.luoshuangfw.io/gpulm-releases/GPULM-5.6.1.7z
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New: OpenImageDenoise GPU denoisers have been enabled for both NVIDIA (through CUDA) and AMD (through HIP). Should speed up the lightmap transcoding phase.
Note: if you are not using this binary patch but building from gpulm-no-luoshuang, follow the instructions in Engine/Plugins/Experimental/GPULightmass/How_to_enable_GPU_denosing_support_on_Windows.txt and Engine/Plugins/Experimental/GPULightmass/How_to_use_Intel_OpenImageDenoise_on_Linux.txt to enable them.
Fixed: crash when ISM lightmap type is set to force volumetric
Fixed: crash when support ray tracing is disabled on mesh assets
Fixed: crash with Water meshes
Fixed: inconsistencies when Nanite ray tracing proxies are enabled
(Update 2025.11.11) Fixed: quality issue caused by using MSAA to render lightmap GBuffers. Now leaking around corners should improve
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Experimental Release 2025.11.12
https://downloads.luoshuangfw.io/gpulm-releases/GPULM-5.6.1.7z
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With the GPU denoiser being 10-15x faster, now it’s time to optimize the lightmap transcoding and encoding part. It was not worth doing as the CPU denoiser was taking the majority of time.
This release optimizes by parallelization. Though, processing many meshes simultaneously can take lots of memory. Let me know if you run into memory issues.
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Hi, I’d really appreciate some help and suggestions on what I can do.
I’m currently working with the base GPU Lightmass plugin in Unreal Engine 5.6, and I also tested the newest UE 5.7 version. I’m getting the same strange artifacts on certain meshes.
I’ve already tested everything I could think of. Is there any optimization or workaround for this?
GPULM-5.6.1 — will this plugin help me solve this problem? If so, is there any instruction or guide on how to install this version of GPU Lightmass?
Update 1
After installing the GPULM-5.6.1 patch, all meshes now have this problem:
Update 2
I managed to get it working, but only under two conditions:
- I had to disable Irradiance Caching
- mesh scale must be set to 1. If the scale is anything like 1.3 or 2, artifacts and speckles appear on the shadows.
What do you think about this? Does anyone else have similar issues?
Update 3
Okay, the problem came back. I’m going to lose my mind, please help.
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If possible I’d like to get your project for testing, as just looking at your screenshots doesnt give much info
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Release 5.7.0 2025.11.14
https://downloads.luoshuangfw.io/gpulm-releases/GPULM-5.7.0.7z
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Really wonderful @yujiang.wang you already have a 5.7.0 plugin. Will test right away.
Edit: tested with several projects the last few hours. Your 5.7.0 release works wonderful. No crashes and no artifacts where the native GPUlm in 5.7.0 does show artifacts and does crash on some projects.
One question though:
First, could you explain all the settings in the GPUlm panel? There are some snippets all over this topic.
Second, could you advise on what settings / values to use for quick calculation of lightmaps and what settings/values for high quality lightmaps?
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I actually don’t have more than what I’ve said in the snippets. I have limited experience as a user to my own software, so all I can say is ‘you just need to explore and try’
@yujiang.wang is there anything you can do for UE 4.27-plus users? UE5.x performance is horrible when it comes to older / less powerful platforms, which require baked lighting. A lot of devs are still on 4.27-plus and not planning to migrate to UE5. GPULM is not that great in 4.27-plus. I am not asking to port 5.7 GPULM to 4.27-plus, but I am asking (on behalf of all devs) to fix 4.27-plus GPULM. Please.
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What are the problems 4.27 GPULM need to be fixed? Some problems cannot be simply fixed (like the quality issue where half of a wall facing outside and being very bright and the other half being dark). Instead, a completely new pipeline needs to be implemented. Like how ‘denoise each chart separately’ resolves the above problem which involves creating a lightmap chart renderer, changing lightmap UV generation algorithm, packing/unpacking lightmap uvs and sending them to the denoiser. Basically to properly fix that problem this entire pipeline has to be ported back.
When communicating with pawel9091 we had some findings which might fix the artifacts when you enable Irradiance Caching. Were you using relatively low GI samples vs IC+FBRG samples? Like 64 vs 128+128? The fix has been included in the latest GPULM-5.6.1.7z and GPULM-5.7.0.7z, also pushed to gpulm-no-luoshuang. You may have some luck trying it. Its basically this one: https://github.com/AlanIWBFT/UnrealEngine/commit/84ad7e2fd5e99aa9616657a59bf893810a282b7a
As I was about to post issues I experienced in UE 4.27.2, I decided to give a spin to this new fork of UE4.27-plus https://github.com/uno1982/UnrealEngine/tree/4.27-plus-meta
Interestingly enough (so far)GPULM works fine there.
Release 5.7.0 2025.11.17
https://downloads.luoshuangfw.io/gpulm-releases/GPULM-5.7.1.7z
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This release fixes a critical issue where ISM instances are picking up wrong instance data:
Update: I’ve fixed the issue with
r.RayTracing.InstanceBuffer.RLE and you no longer need to set it.
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@yujiang.wang Does GPUlm also calculate the Volumetric Lighting? If so, could it be that changing the Detail Cell Size (in WorldSettings) is broken in 5.7 OR that visualizing the Volumetric lightmaps always shows the default density of the samples?
I’m testing using VLMs for ‘lighting‘ the foliage and I’m trying smaller cell sizes to add more realism in the lighting.
Use the detail cell size setting in GPULM panel
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