Why do my UV maps appear improperly when I bake lighting?


Whenever I run Lightmass bake, it seems to mess with the UV maps and they appear like the image shown. They work fine in Unity when baked.

Anyone else run into this issue?

Yes, i have same problem.

Do you have a lightmass importance volume in the level? And are you sure you set the correct UV channel for lightmaps?

I’ve had similar problens. Have you tried generating Unique UVs to see if it’s an issue with your LightMaps?

Broblem fix, need create UV for model.

@ Archii did you miss the UV map on the tower at the side and the part where I said it looks fine in Unity? Also it’s fine before lightmapping :D…

@ Jacky I’ll try the lightmass importance volume as this is a large scene and it has been complaining about it.

I really wouldn’t like to generate new UV’s for the 28,000 assets we have. If I have to that’s a UE4 deal breaker.

Lightmass importance volume is a must. Create one large enough to get all of your assets and lights in it.
You can check and set the UV channels of your meshes when you open them in static mesh editor. They should be fine as long as there are no overlapping UV’s.

Maybe this help

Light rebuild

Collision complexity has nothing to do with this, and when you turn a mesh to Movable then there is no point in baking the lights, since it uses dynamic lighting.

So I went back to it, I created a Lightmass importance volume and started going through each mesh and generating Unique UV’s… It’s not really helped at all, I even tried going back into Modo and using different types of UV wrapping.

It’s not made a difference.

Well it has to be something to do with the Lightmap UV’s, I tried again playing with the UV index’s but it’s still far from right. After regenerating UV’s in different channels for all mesh’s at least some of them are getting light. It shouldn’t be this difficult should it?

It shouldn’t be this problematic, but i must say i’m not familiar with Modo pipeline.

Try this; use a single UV channel with no overlapping faces, for the sake of testing. Import a couple of meshes like that and see if they work properly. If they do, then the problem is related to creating and keeping the second UV channel in Modo. If they still dont work then post the screenshot of your meshes UV layout inside the static mesh editor please.

Yes as you say, when I import for a singular UV map works fine, if I don’t lightmass get’s messed up.

Ok so now we know the route cause, what can I do about it?

There are a couple of things you can do but i don’t think you’ll like them…

First, you can try switching to Blender, Max or Maya.

Second, You can export your model twice with each UV channel in each export. Then import them to another modeling software and copy/paste the lightmap UV’s.

Third, you can try using a single channel with no overlapping UV’s and set your textures according to this UV layout of course.

Fourth, You can generate unique UV’s inside the editor, but it gives messy results most of the time.

Fifth, you can go fully dynamic lighting.

Thanks Jacky, We can’t switch we have 15 licences of Modo, Nuke and Mari. Messing with all 28,000 models would just be a major headache. I might see if we can get UE4 with Enlighten hooked in. Or we’ll continue on with Unity, much appreciate your time. Thank you so much for your replies…

Fair enough, none of the things i said make sense for 28k models. :\ Did a quick search on google about this and apparently Modo can use the second UV channel inside Modo but nobody can export them properly. If the game is taking place mostly in open world, i’d suggest keeping an eye out for LPV and carry your project over to UE4 when it is polished(if it is not too late until then, that is)

Good luck!


Modo can export multiple UV maps just fine with FBX 2006/2010/2013. So if your using Modo 601/701 you should be good to go.

I’ve never used Modo(also said that earlier in this thread), just saw people having this kind of issue on Google. Maybe something is wrong with ShadowKingGames’s pipeline though so you can help them out. :slight_smile: