# Problem with lightmaps

**URL:** <https://forums.unrealengine.com/t/problem-with-lightmaps/80126>\
**Category:** Rendering\
**Tags:** unreal-engine\
**Created:** [December 8, 2016, 10:48am UTC](https://forums.unrealengine.com/t/problem-with-lightmaps/80126 "2016-12-08T10:48:27Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![Thormann3D](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Thormann3D](https://forums.unrealengine.com/u/Thormann3D)\
**Post date:** [December 8, 2016, 10:48am UTC](https://forums.unrealengine.com/t/problem-with-lightmaps/80126/1 "2016-12-08T10:48:27Z")

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Hi there,

once again a thread about lightmaps in UE4 (4.14). I cant get rid of the seams:

![513a9f4d2517b56513e76f50bd4f2395f2e3d47e.jpeg](https://d1ap1mz92jnks1.cloudfront.net/images/transparent.png)  
(rendered with preview, but the seams are also in the production renders)

I created a simple box: 400_400_40. I created a second uv channel for the lightmap, with snapping and spacing.

![3838e2de76af63184849859ae3d1c7bc81cd9cd8.jpeg](https://d1ap1mz92jnks1.cloudfront.net/images/transparent.png)

Here are also the settings:

![b03bbaa302bf555193c024b3f1b248ae962a98c7.jpeg](https://d1ap1mz92jnks1.cloudfront.net/images/transparent.png)  
 ![aa7a4a4b7a43db542454920168fe665b1ca5ec14.jpeg](https://d1ap1mz92jnks1.cloudfront.net/images/transparent.png)

There is a lightmass importance volume, a directional and sky light (both stationary). Even a 1024 lightmap resolution.

Im simply dont get it.

This floor is 4\*12 meters. Should i do for this a single mesh? But this modular pipeline should also work.

Link for the Mesh:

> **[Dropbox - File Deleted](https://www.dropbox.com/s/cptgwyjyj5omxw3/SM_ARCH_Block_400x400x40_a_01.FBX?dl=0)**
>
> Dropbox is a free service that lets you bring your photos, docs, and videos anywhere and share them easily. Never email yourself a file again!

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**Author:** ![NasteX](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@NasteX](https://forums.unrealengine.com/u/NasteX)\
**Post date:** [December 8, 2016, 11:13am UTC](https://forums.unrealengine.com/t/problem-with-lightmaps/80126/2 "2016-12-08T11:13:07Z")

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You need few settings changes on the lightmass tab:

- Static Lighting Level Scale - 0.1
- Indirect Lighting Quality - 3-4 (10 is hardcore)
- Indirect lightning smoothness - 0.6

Make sure you have light portals on each window. Also I think the grid resolution of the UVs is too low, make sure the grid is the same resolution you are targeting for. Better make a 256x256 pixels grid texture, add it inside the UV unwrapping editor (on checker pattern dropdown menu, choose pick texture), and then choose “Pixel snap” (not Grid snap). Make sure that the min distance between uv islands is 2 pixels, if you want to calculate the spacing value and automize stuff 2/256 = 0.0078 this is the spacing for 2 pixels in 256 pixels grid.

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**Author:** ![Thormann3D](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@Thormann3D](https://forums.unrealengine.com/u/Thormann3D)\
**Post date:** [December 8, 2016, 1:15pm UTC](https://forums.unrealengine.com/t/problem-with-lightmaps/80126/3 "2016-12-08T13:15:53Z")

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> [@NasteX;634879](#):
>
> You need few settings changes on the lightmass tab:
> 
> - Static Lighting Level Scale - 0.1
> - Indirect Lighting Quality - 3-4 (10 is hardcore)
> - Indirect lightning smoothness - 0.6
> 
> Make sure you have light portals on each window. Also I think the grid resolution of the UVs is too low, make sure the grid is the same resolution you are targeting for. Better make a 256x256 pixels grid texture, add it inside the UV unwrapping editor (on checker pattern dropdown menu, choose pick texture), and then choose “Pixel snap” (not Grid snap). Make sure that the min distance between uv islands is 2 pixels, if you want to calculate the spacing value and automize stuff 2/256 = 0.0078 this is the spacing for 2 pixels in 256 pixels grid.

Thanks. It works. I need to test this under harder conditions 😉

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**Author:** ![NasteX](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@NasteX](https://forums.unrealengine.com/u/NasteX)\
**Post date:** [December 8, 2016, 1:55pm UTC](https://forums.unrealengine.com/t/problem-with-lightmaps/80126/4 "2016-12-08T13:55:05Z")

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Do it, you will learn a lot by testing under harder conditions. 😉

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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:** [December 8, 2016, 5:03pm UTC](https://forums.unrealengine.com/t/problem-with-lightmaps/80126/5 "2016-12-08T17:03:10Z")

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Also, don’t construct things that way, there’s actually several ways that is more inefficient.

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