# Strange Lightmap artifacts on simple geometry

**URL:** <https://forums.unrealengine.com/t/strange-lightmap-artifacts-on-simple-geometry/321968>\
**Category:** Rendering\
**Tags:** lighting-error, Lightmass, unreal-engine, Lightmap, lighting-problem, Lighting, question\
**Created:** [June 16, 2015, 6:53am UTC](https://forums.unrealengine.com/t/strange-lightmap-artifacts-on-simple-geometry/321968 "2015-06-16T06:53:53Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![CASA\_MT\_1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@CASA\_MT\_1](https://forums.unrealengine.com/u/CASA_MT_1)\
**Post date:** [June 16, 2015, 6:53am UTC](https://forums.unrealengine.com/t/strange-lightmap-artifacts-on-simple-geometry/321968/1 "2015-06-16T06:53:53Z")

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Hey there,

I am relatively new to using UE 4, so I hope this issue has not been discussed before. I used search on the answerhub and in google, but could not find any solution to my problem.

Problem:

I have a simple szene-setup with a floor, a room and a roof. The lighting works pretty well on every asset except for the roof, althoug it has a veeeeeeeery simple geometry. It is little more detailied by now, because I thought it might be caused by not having enough polys or something, but that did not work either.

The result looks like on every quad-edge there seems to be an error (looks like a shadow). I used a customized lighting UV, just so that everything could be computed in the best way. You can see both screenshots attached. I don’t know what I do wrong, because I did nothing different than when importing the floor and the room and these two assets do not behave like the roof.  
Any ideas?

 ![46558-02.jpg](https://d3kjluh73b9h9o.cloudfront.net/original/4X/9/d/4/9d43889ae4f8e281cfccfa15aa36066f96dd08d2.jpeg)

 ![46557-01.jpg](https://d3kjluh73b9h9o.cloudfront.net/original/4X/6/3/2/6327dbabd7f3e0e443017c83a9fe6de4786d61ce.jpeg)

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**Author:** ![anonymous\_user\_2ed5b4c7](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_2ed5b4c7](https://forums.unrealengine.com/u/anonymous_user_2ed5b4c7)\
**Post date:** [June 16, 2015, 7:06am UTC](https://forums.unrealengine.com/t/strange-lightmap-artifacts-on-simple-geometry/321968/2 "2015-06-16T07:06:22Z")

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Hi!

Modular building has some issues. How to fix it you can read in this thread:

> **[Modular Asset Lighting Problem](https://forums.unrealengine.com/showthread.php?46269-Modular-Asset-Lighting-Problem)**
>
> Hello all! I just started working on my first set of modular assets (which are primarily different sized tiles) and I’ve gotten them to fit correctly and everything but now the problem is lighting. It is being lit differently on some tiles. Also,...

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<div class="post-metadata">

**Author:** ![CASA\_MT\_1](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@CASA\_MT\_1](https://forums.unrealengine.com/u/CASA_MT_1)\
**Post date:** [June 16, 2015, 9:05am UTC](https://forums.unrealengine.com/t/strange-lightmap-artifacts-on-simple-geometry/321968/3 "2015-06-16T09:05:53Z")

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Thanks for the link, I got rid of this problem although I did not really do it the way it is described there.  
I refined my lighting UV and re-imported the mesh. After the re-import, UE4 auto-generated a UV-channel 2 with new orientations of the UV-islands.  
Instead of using my own created channel (which would be channel 1), I used the new auto-generated. The result is pretty good. With my own created channel, it still does not work though, not sure why -.-

But thanks anyway for the quick response 😉