Luoshuang's GPULightmass

Same answer as above.

4.20.2 and 4.20.3 share the same core, so it’s the same binary. You can use the bat installer and it’ll do it for you.

this looks really nice and clean. if you don’t mind what is your lightmass settings ?

You may want to read the first post, lightmass settings other than bounces are ignored by GPU.

This is a downloadable demo scene from the “multi-bounced skylight” thread if you want to try it yourself.

One thing I’m curious about, the gist I’m getting is that Swarm works just fine with this, but is the scene split up in any way, or will the scene take up equally much vram on any gpu used?
Like if I’ve got a scene that takes up 9GB vram, and I can lightmap it just fine on my desktop, would it work in swarm if I also pushed it to a secondary desktop with ~8GB?

After all, the entire scene has to be loaded on each pc, but since there’s less work to do ( fewer texels to lightmap, etc, per gpu.) I wonder if the vram usage per pc goes down a bit or not.

edit: I ran a couple tests, and it looks like Vram usage is completely unaffected. Though atleast the servant-pcs use less vram, much like when ordering a lightmap from commandline / without opening the editor.

Hi Luoshuang I have to report that in condition of little light even in extreme quality appear these splotches. There is a way to solve them or I have to return to CPU? It’s truly a pity because I’m in love with GPU lightmass speed and it’s indirect shadows

Hi. First of all - Lighmass GPU is a miracle. And there is no way back to CPU. It’s superfast and clean. I’m doing some personal archviz project - just a small house in a natural environment. I almost finished the house and it looks great (and takes about 5 min on Extreme with my 1080). I started to build environment and i’ve got some lightmap artifacts on the foliage and other objects. UVs are fine and test CPU bake looks exactly as it should be. Any thoughts?

Interior test (it shows superiority GPU over CPU - on CPU it would take hours to that quality bake):

It’s most likely because your LODs are poking out. From the OP:

Thanks. You are right about LODs interference. I already figure out it by myself - artefacts looks like all LODs are baked together. Here is a proof - I just deleted all LODs on selected object

As most people I read OP very quickly and forgot about this issue.

Did you make the lods yourself OR did you have UE make them? On several objects I dont have problems with HISMs & GPU lightmass when UE makes the lods.

Hi. I am using the GPU lightmass for about a month now and everything worked just perfectly. Great job thanks a lot for such an improvement. But yesterday I installed the new RTX card and now my PC crashes every time I try to build the lighting. I installed the latest drivers and used the automatic script installer where I passed all the checks so I don’t see any obvious problem. I also reinstalled UE4 4.20.3 and cleared the cache in the swarm agent. Any suggestions what could be the problem? Thanks.

I’ve also experienced this, but it doesn’t always work. But it got rid of 98% of the cases.


I was using Nvidia old driver when I had this error. Please update new driver and everything will work smoothly. Thanks Situx.

In case you have this error, update driver.

Hi ,

I am also using a custom built 4.19 fro, github, here is the link: , I am not sure how do you change the file to install this gpu lightmass.
I have tried the latest script for 4.20.2, but because I am using quadro M5000M the driver can not reach version 398.26. So I have to stick with 4.19. I am not sure how to change the LightmassConfiguration.bat to make it work with either Unreal 4.19.2 version or the Unreal VXGI2-4.19.


Nothing more than a big thank you for the GPULightmass !!

Harder, Better, Faster Stronger !!!

Any idea how to fix the blocky shadows where geo meets up?

As I know and you can read on the 1st page of this topic, this new alg. of baking needs more Light Map resolution (is resolution sensitive). For a single bottom cushion you have here ( I hope that you have split whole couch on parts) you should use sth min 256 and better if 512px of resolution ( for that single part). I have checked it and when I have some ‘stairs-like’ shadow then just double the resolution and I have it smooth enough. GPU Lightmap bake is fast enough to handle well 512px+ LM resolutions w/o waiting too much longer as it was with the CPU bake.

@Loushouang - emissive materials for static meshes do not emit any light for bake. ie. when I use power of 1 (material unitless emission power ) and it is enough for the brightness effect when camera looks at it, the nthe effect on surrounding object is NONE. Even when I crank up the value for Emission multiplier in static mesh parameters (i.e. from default 1 to 500). No effect at all.
Do I do sth wrong or it does not work correctly with GPUlm for 4.20.3 ?

@Loushouang - ETA & ligthmap bake statistics.

I have to say that ETA is computed wrong. Cause when I have many objects with many LODs then the GPU computation time for bake at single pass is much shorter that CPU mipmap generation (or whatever CPU is doing after every single pass of GPU computation ). And your ETA is based only on GPU work (as I have observed).
So notice dear community that even if somebody has very powerful GPU card then strong (very, very multicore setup) for CPU is strongly recommend when scene has objects with many LODs (many LODs for very complex vertex structures 60-100k+ for LOD0).

Unfortunately this kind of bake time computation (or summarization - dunno how to describe that) based only on GPU work gives wired results in statistics.
Statistics are very helpful sometimes when we need to check what was baked so long for example.
And they contain very insanely low bake times (?!) according to the real duration of whole baking process.

This is not something with high priority on TODO list. But maybe it could be fixed when you will have nothing to improve with your fantastic GPU bakery :slight_smile: for which I THANK YOU VERY MUCH MASTER Loushouang !

@Situx - I would like to ask if I your BATCH manager for Lightmass I will download every new update of GPU Lightmas automatically to my local machine when you upload it to your distribution place ?

Technically possible, but any future update will need to have its hashes calculated to properly detect what version you are running.

However, It is not intended that way. The installer is meant to make it easy for non-savy users, or lazy ones like me who either has to make CPU bakes now and then, or install GPU in many computers. Theoretically, you can “clone” the installer’s github repository, then each time I upload a change you can pull the changes, but not automagically.

If there is enough interest I may look onto something like that, but would depend on the use case and the free time I have available. Also my guess is this won’t take long to get integrated into the engine (this is amazing tech). At this point anyway I don’t believe there would be much more updates before 4.21 starts previewing, at which point we’ll probably need another GPU heavy update, including the batch file, or even (hopefully) see some GPU baking integrated into the engine which will make the installer obsolete.