Lightmass under 4.14 MUCH slower.


I am wondering if anyone else is seeing that lightmass is taking much longer under 4.14 than it did under previous versions?

Our lighting build went from about 20 minutes to 200+ minutes on preview build quality for the same scene. (I don’t actually know how long it will take since it’s still running!)



It seems to be the same to me.

You can use the Lighting Build info from Statistics for a comparison and to see what meshes are taking the longest to build. If you have a scene that hasn’t changed between 4.13 and 4.14 at all that may a good indicator what is taking the longest to build and where the problem potentially lies. If you’ve upgraded your project to 4.14 and made changes I’m not sure that’s the best test case to just say that lighting is taking longer. This can help you investigate what is taking the longest to build on your machine.

Thanks. I’ll take a look.

But we haven’t changed anything except the engine version. It appears that lighting never finished on my machine, but it does eventually finish on other machines. In the visual studio output window I’m seeing the last lighting message followed by a bunch of threads ending (probably not relevant).

Then unreal sits at 99% build lighting forever. The texture gathering stage never happens. It never finishes.

Do you have any thoughts on why this might be happening?


Does this happen with other projects or scenes, or just this one in particular? Typically the easiest thing to try first is to uninstall and reinstall the editor. If the scene is simple, you could try recreating it. Often times converting projects from one version to another introduces extra bugs or issues. You could also try deleting the last static meshes mentioned to see if that’s causing issues (SM_WashingMachine for example).

If it is one static mesh breaking the baking project, and you don’t know which one it is, you could always try the method of deleting half the static meshes and seeing if it bakes, and then deleting the other half and seeing if that bakes, and then going through half of those halfs, etc.

I did discover the object that was causing problems only on my machine. The same object lights on other machines just fine.

It would be nice to know why it only fails on my machine though…mysteries…

Can anyone from Epic answer if the lighting process makes any use of the GPU? One thing different on my machine is I have the latest drivers from nVidia.