Why is my lightmap UV overlapping?

I tried many times but keep getting errors. How can I fix this?

Hi Dahquest187,

The Unreal Engine uses precomputed lighting that is baked into a texture called a lightmap. You will need to make sure you created a second UV channel for your mesh as this is where the lightmap information will be stored. If there isn’t one set up the engine will use your texture UV slot as the default lightmap UV which can cause the errors you’re getting.

You can find information on how to setup light maps from Epics documentation HERE.

Some other good references are can be found on Hourences website www.WorldofLevelDesign.

If you’re not sure how to setup a second UV channel you can always search YouTube for your specific 3D softwares method of doing so.

If you have any other questions please feel free to post them here and I will do my best to help you!


Sorry if I did not explain it properly but I have 2 uv channels with light map inside 3ds I also have no overlapping faces but once imported into unreal engine 4 it says I have overlapping faces I do not understand this not one bit

I am using 3ds 2012, Unreal Engine 4 and Photoshop CC

only 2 uv’s

I don’t know how to use Blender it’s way more complicated than 3ds

only 2 uv’s and blender is complicated

I deleted them out of frustration was going to switch back to cry engine because I am having so many problems with UE4

every model I imported had lightmap errors

even the ones I didn’t make

the link you sent me I watched that one last night

Do your probably have 3 uv channels?

1st for texture
2nd for lightmap
3rd for texture

Have you already watched a tutorial how to create a proper lightmap, because normally when everything isn’t overlapping it should work?

Otherwise you could also export your model to blender and there you can try it out if it probably works after you have imported it into the UE4 from blender:

Hmm, then it is pretty strange. But on your 2nd uv channel is just the lightmap? And could you probably post a image of your 2nd uv?

Hi Dahquest187,

Here is a link to how to setup a second uv channel for lightmapping from 3Dmotive. (Link Here)

If you wanted you could also upload any one mesh you are having trouble with or create a simple mesh that is causing the same issue. I can take a look at it and tell you exactly what is wrong.