"Lightmap UVs are overlapping" error not going away?

Carabiner

I'm having an issue with baking lightmaps, I keep getting an "Lightmap UVs are overlapping by 86.5%" error even if I select a different UV set for the light mapping process to use. Help? This is my first project in Unreal, so I'm definitely still learning!

This is what the version with the lights built looks like



Imgur album with more images and description/screenshots here:

http://imgur.com/a/OjlIP

xX0r1oNXx

Do any of the UVs in your LightMap UV sit on top of one another? Without the option toggled on, it may be hard to tell.
That UV snapshot looks like Maya, am I correct?

Carabiner

Yeah, I checked the lightmap view and everything is green/blue. The thing is, I keep getting the 86.5% error, even if I select a different UV map to be used and save the mesh details. I wonder if maybe I'm not correctly telling the engine which map I want to use for lightmaps?

The UV snapshot in the last one is in Maya, but I'm actually using the unique UVs that were generated by Unreal (http://i.imgur.com/jtHB246.png).

Cay

do you use the 1st channel for your normal uvs and 2nd as the generated? if so.. you need to insert the correct channel number into "lightmap coordinates" -field somewhere in the mesh's settings so ue4 knows which channel to use for lightmapping

xX0r1oNXx

Sorry for the long reply time. If you've not solved your issue yet, could you post a snapshot of your UVs from Maya? That might help clear some things up.

toren3d

Are you using 4.5.1? I ask because I never had this sort of issue until then. I read on a few of the Unreal Answers topics that this is a known issue (they are doing an auto generate lightmap UVs starting in 4.5 and apparently it has a few bugs). I ended up using the Global Illumination method, skipping lightmass altogether, to solve the issue. You can read more on how to enable that here: https://forums.unrealengine.com/showthread.php?530-How-to-enable-Light-Propagation-Volumes-GI-WIP-AND-BETA

Xendance

The overlap warning is also affected by the lightmap resolution. If you use a too low resolution and don't have enough padding between the islands, you'll get that warning.