# What's the difference between overlapping and wrapping uvs?

**URL:** <https://forums.unrealengine.com/t/whats-the-difference-between-overlapping-and-wrapping-uvs/401911>\
**Category:** Rendering\
**Tags:** overlapping-uvs, Lightmass, unreal-engine, question\
**Created:** [August 13, 2017, 2:36pm UTC](https://forums.unrealengine.com/t/whats-the-difference-between-overlapping-and-wrapping-uvs/401911 "2017-08-13T14:36:45Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Lou345](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Lou345](https://forums.unrealengine.com/u/Lou345)\
**Post date:** [August 13, 2017, 2:36pm UTC](https://forums.unrealengine.com/t/whats-the-difference-between-overlapping-and-wrapping-uvs/401911/1 "2017-08-13T14:36:45Z")

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Hi,

I was getting errors about “Object has overlapping uvs” on my meshes not having secound UV channels, I fixed that following the advice on here by creating or importing a second UV channel without any overlap. I then chose this light channel in the lightmass index, but after building lighting now the error has changed to “Object has wrapping uvs”. What’s the difference here?

Are wrapping UV’s okay?

Cheers,

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**Author:** ![Ninjin](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Ninjin](https://forums.unrealengine.com/u/Ninjin)\
**Post date:** [August 13, 2017, 5:23pm UTC](https://forums.unrealengine.com/t/whats-the-difference-between-overlapping-and-wrapping-uvs/401911/2 "2017-08-13T17:23:09Z")

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No, wrapping UVs are not okay. I’m not an artist, but I hope my Paint Skills are enough for this.

 ![](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/e/b/2eb36e6eff687913dc47b637ef93ebb4a4b3bc1d.png)

So, make sure your lightmap UVs are in the 0-1 space.

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**Author:** ![Lou345](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Lou345](https://forums.unrealengine.com/u/Lou345)\
**Post date:** [August 15, 2017, 3:01pm UTC](https://forums.unrealengine.com/t/whats-the-difference-between-overlapping-and-wrapping-uvs/401911/3 "2017-08-15T15:01:44Z")

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Excellent, that makes total sense! Thanks alot for your answer, your paint skills are more than enough =)

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**Author:** ![anonymous\_user\_8312749a](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_8312749a](https://forums.unrealengine.com/u/anonymous_user_8312749a)\
**Post date:** [August 16, 2017, 1:53am UTC](https://forums.unrealengine.com/t/whats-the-difference-between-overlapping-and-wrapping-uvs/401911/4 "2017-08-16T01:53:57Z")

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just to further expand on this. for the lightmap all objects must be unwrapped in the 0-1 space for both U and V and must not be overlapping. wrapping and overlapping are fine for other purposes (although not for baking normals).

and please mark this problem as answered if it is.

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**Author:** ![Lou345](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Lou345](https://forums.unrealengine.com/u/Lou345)\
**Post date:** [August 16, 2017, 10:30am UTC](https://forums.unrealengine.com/t/whats-the-difference-between-overlapping-and-wrapping-uvs/401911/5 "2017-08-16T10:30:02Z")

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Hi Nuclear,

Thanks for your input! And yes, I already marked as answered after my comment.