# Epic's GPUlightmass **URL:** \ **Category:** Rendering\ **Tags:** unreal-engine\ **Created:** [March 5, 2020, 12:52pm UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357 "2020-03-05T12:52:56Z")\ **Posts on this page:** 20\ **Page:** 46
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 10, 2026, 8:31am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/918 "2026-05-10T08:31:32Z")
Surface lightmaps can be attached to them, though you probably need to toggle some settings about two sided in both material and component lightmass settings ---
**Author:** ![stamisme](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@stamisme](https://forums.unrealengine.com/u/stamisme)\ **Post date:** [May 11, 2026, 10:04am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/919 "2026-05-11T10:04:07Z")
THANK YOU!!! ---
**Author:** ![stamisme](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@stamisme](https://forums.unrealengine.com/u/stamisme)\ **Post date:** [May 11, 2026, 10:07am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/920 "2026-05-11T10:07:00Z")
![image](https://d3kjluh73b9h9o.cloudfront.net/original/4X/8/e/9/8e9b9da38d0c580a7bc9b71ec106f4547d332256.jpeg)is this possible in GPU lightmass? ---
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 11, 2026, 10:26am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/921 "2026-05-11T10:26:26Z")
It is implemented but only for non Substrate materials: [Epic's GPUlightmass - #357 by YujiangW](https://forums.unrealengine.com/t/epics-gpulightmass/139357/357) I haven’t tested it for Substrate so idk if the automatic Substrate material converter can make it work ---
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 12, 2026, 3:09am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/922 "2026-05-12T03:09:10Z")
# Experimental: Graphical Installer 5.7.4 2026.05.10 [https://downloads.luoshuangfw.io/gpulm-releases/GPULM-5.7.4-2026.05.10.exe](https://downloads.luoshuangfw.io/gpulm-releases/GPULM-5.7.4-2026.05.10.exe) [Back to release list](https://forums.unrealengine.com/t/epics-gpulightmass/139357/667) ![GPULM5.7.42026.05.10.tmpcSGzd1fyn6](https://d3kjluh73b9h9o.cloudfront.net/original/4X/f/b/c/fbc7c2ccef2fc5b7afcfe5d70a03785ab4e5eba2.png) Now you can install GPULM with this installer. It backups engine files so they can be restored during uninstall: ![QKocXIdF5F](https://d3kjluh73b9h9o.cloudfront.net/original/4X/3/8/1/3818f5d96a3ded9cd1846ac43c8e5e4ce2534a83.png) ![j9m80Ji7tw](https://d3kjluh73b9h9o.cloudfront.net/original/4X/4/4/d/44df54553464f55b27c91af38d3da1d99e6c1894.png) This isn’t just a QoL change; in the future I will start to modify engine runtime files, and I expect many of them will have only very small difference in binary. Packing all the changed files in a 7z archive will be infeasible because of size. This installer uses [HDiffPatch](http://github.com/sisong/HDiffPatch) to patch the engine. The installer won’t try to restore files if it finds the files don’t match the version it has patched. ---
**Author:** ![stamisme](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@stamisme](https://forums.unrealengine.com/u/stamisme)\ **Post date:** [May 12, 2026, 4:19am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/923 "2026-05-12T04:19:37Z")
any info on the next updates? also wanted to ask, should i credit you in the reveal announcement of a project i’ve been involved in? ---
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 12, 2026, 4:23am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/924 "2026-05-12T04:23:35Z")
> any info on the next updates? I will focus primarily on VLM. > also wanted to ask, should i credit you in the reveal announcement of a project i’ve been involved in? I’d appreciate that. ---
**Author:** ![stamisme](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@stamisme](https://forums.unrealengine.com/u/stamisme)\ **Post date:** [May 12, 2026, 4:26am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/925 "2026-05-12T04:26:26Z")
👍 also, its a long stretch but since you’ll start to edit engine files, it would be EXTREMELY helpful if we could get some sort of “Do NOT Render with VLMs” checkbox on actors we’ve been really struggling with lightbleeding into large actors like moving trains ---
**Author:** ![stamisme](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@stamisme](https://forums.unrealengine.com/u/stamisme)\ **Post date:** [May 12, 2026, 4:33am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/926 "2026-05-12T04:33:56Z")
i think at some point, i tried a horrible fix by rendering the train interior as unlit and then baking the lighting in blender and using the lightmaps in the shader ---
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 12, 2026, 4:34am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/927 "2026-05-12T04:34:55Z")
Did you try to force the train to use surface lightmaps? ---
**Author:** ![stamisme](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@stamisme](https://forums.unrealengine.com/u/stamisme)\ **Post date:** [May 12, 2026, 4:36am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/928 "2026-05-12T04:36:46Z")
yeah, but nothing changed on our end after trying that ---
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 12, 2026, 4:54am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/929 "2026-05-12T04:54:23Z")
Here, force surface makes the cube retain its lightmap. if you move the cube directly in the editor its lightmap will be invalidated though. this is driven by a sequence ---
**Author:** ![stamisme](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@stamisme](https://forums.unrealengine.com/u/stamisme)\ **Post date:** [May 12, 2026, 4:58am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/930 "2026-05-12T04:58:33Z")
but this now gives us light bleeding from the lightmap or do you mean i should put the train actor into a pitch black area and then teleport it to the needed area at runtime? ---
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 12, 2026, 4:59am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/931 "2026-05-12T04:59:32Z")
yeah you do need to sacrifice something ---
**Author:** ![stamisme](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@stamisme](https://forums.unrealengine.com/u/stamisme)\ **Post date:** [May 12, 2026, 5:00am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/932 "2026-05-12T05:00:37Z")
at the very least, if that means it’ll be pitch black interior wise i can handle that, since my goal is to have no light bleeding at all and then light up the interior with movable light actors ---
**Author:** ![AndrewSlugger](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@AndrewSlugger](https://forums.unrealengine.com/u/AndrewSlugger)\ **Post date:** [May 26, 2026, 12:46am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/933 "2026-05-26T00:46:42Z")
Hello, I wonder how to install GPULM for U.E. 5.7.4. Does anybody have a guide of what to do? I overwrote the folder but still didn’t get it. What to do next? ---
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 26, 2026, 6:11am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/934 "2026-05-26T06:11:33Z")
First use the verify option in the launcher to restore your engine files, then try to use the graphical installer: [Epic's GPUlightmass - #922 by yujiang.wang](https://forums.unrealengine.com/t/epics-gpulightmass/139357/922) ---
**Author:** ![AndrewSlugger](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@AndrewSlugger](https://forums.unrealengine.com/u/AndrewSlugger)\ **Post date:** [May 28, 2026, 11:35pm UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/935 "2026-05-28T23:35:43Z")
I’m really new to it. I wish to know exactly what to do step by [step.](http://step.So)I think it would be helpful if there were some instruction on how to install it properly. I don’t really understand how it works. By default I have CPU light baking; after overwriting folders using the new .exe installer, it’s still baking with the CPU. (I turn off Lumen, I turn on Allow Static Lighting, I turn off Global Illumination Method to None, and I set Reflection Method to None.) I set lighting quality to production level, and it’s still baking using the CPU. CPU: AMD Ryzen 7 9800X3D 8-Core Processor GPU: NVIDIA GeForce RTX 5070 Ti. ---
**Author:** ![yujiang.wang](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yujiang.wang](https://forums.unrealengine.com/u/yujiang.wang)\ **Post date:** [May 29, 2026, 3:05am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/936 "2026-05-29T03:05:31Z")
The patch is a fix to the official GPU Lightmass. What you need is [GPU Lightmass Global Illumination in Unreal Engine | Unreal Engine 5.7 Documentation | Epic Developer Community](https://dev.epicgames.com/documentation/en-us/unreal-engine/gpu-lightmass-global-illumination-in-unreal-engine) . There are a few UI and functionality changes. ---
**Author:** ![AndrewSlugger](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@AndrewSlugger](https://forums.unrealengine.com/u/AndrewSlugger)\ **Post date:** [May 29, 2026, 3:48am UTC](https://forums.unrealengine.com/t/epics-gpulightmass/139357/937 "2026-05-29T03:48:16Z")
Thank you sir! [Previous page](https://forums.unrealengine.com/t/epics-gpulightmass/139357.md?page=45) [Next page](https://forums.unrealengine.com/t/epics-gpulightmass/139357.md?page=47)