# Lightmap issue between 2 modular wall asset

**URL:** <https://forums.unrealengine.com/t/lightmap-issue-between-2-modular-wall-asset/98216>\
**Category:** Rendering\
**Tags:** unreal-engine\
**Created:** [August 10, 2017, 7:46pm UTC](https://forums.unrealengine.com/t/lightmap-issue-between-2-modular-wall-asset/98216 "2017-08-10T19:46:15Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![yanggaizhi](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yanggaizhi](https://forums.unrealengine.com/u/yanggaizhi)\
**Post date:** [August 10, 2017, 7:46pm UTC](https://forums.unrealengine.com/t/lightmap-issue-between-2-modular-wall-asset/98216/1 "2017-08-10T19:46:15Z")

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Hello guys,  
I have a question regarding light map. I have created a modular wall asset. I took the same wall asset and cut a hole in the top middle area.  
But when I put the wall assets together, it create this very distinct shadow seam ( marked in red ).

Before I had the same light map uv as before and it has the seam, I then tweak the uvs and have snapped my light map uv to the grid but it doesn’t seem to help.  
I’m wondering why with the same asset, but modifying the mesh cause such lightmap seam in lighting ?

thanks ![fa56fc33f0d3e756e8216297493c90af98c6dbb7.jpeg](https://d1ap1mz92jnks1.cloudfront.net/images/transparent.png)

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**Author:** ![darthviper107](https://d1ap1mz92jnks1.cloudfront.net/user_avatar/forums.unrealengine.com/darthviper107/32/710746_2.png) [@darthviper107](https://forums.unrealengine.com/u/darthviper107)\
**Post date:** [August 10, 2017, 8:14pm UTC](https://forums.unrealengine.com/t/lightmap-issue-between-2-modular-wall-asset/98216/2 "2017-08-10T20:14:51Z")

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Can’t see the attachment yet but it’s probably this issue:

> **[A new, community-hosted Unreal Engine Wiki](https://forums.unrealengine.com/t/a-new-community-hosted-unreal-engine-wiki/141494)**
>
> After over a year in maintenance mode, the official Unreal Engine Wiki is now permanently offline. These resources now live on a new community-run Unreal Engine Community Wiki — ue4community.wiki! You will be able to find content from the official...

Best fix is to combine simple meshes since it’ll fix that issue and it will improve performance by reducing draw calls.

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**Author:** ![yanggaizhi](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@yanggaizhi](https://forums.unrealengine.com/u/yanggaizhi)\
**Post date:** [August 10, 2017, 11:44pm UTC](https://forums.unrealengine.com/t/lightmap-issue-between-2-modular-wall-asset/98216/3 "2017-08-10T23:44:49Z")

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Thanks for the reply,

I have updated the url, hope you can see the attatchment. I had this same lightmap issue when I didn’t know about the lightmap uv, and the lightmap seam is mostly fixed when I created the lightmap uv.

I didn’t know why putting 2 version types of wall ( 1 with the hole ) side by side will cause the seam again. Increase the lightmass quality doesn’t seem to fix it, so I think there is something I did wrong