What is Min Lightmap Resolution?

Development Rendering
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1

I would like to understand what the Min Lightmap Resoution setting does. You find it in the Object editor in the LOD0 (or up) settings under “Build Settings”.

What I found was this:
“Min Lightmap Resolution = This is the smallest size you would want your lightmap resolution to be.”
under this link here: https://wiki.unrealengine.com/LightingTroubleshootingGuide

Do lightmaps have a dynamic size, that can vary between the resolution you set under the static mesh settings and the LOD0 settings?

thanks in advance

2

Hi Ground Studios,

Lightmaps once baked after a light build are not dynamic in their size. They will be treated like other textures and use mipmaps to scale down their resolution at certain distances to help with texture memory usage.

The Min Lightmap Resolution setting is a property of the Build Settings in each LOD. These build settings are just settings that can be used when generating things for that load such as generating Lightmaps within the editor. This does not set your lightmap resolution directly. This is a value used to create that resolution lightmap when you hit the apply settings button.

Lightmaps are meant to be static and do not support being switched out dynamically with different sizes.

Thank you!

Tim

3

Hi Tim, thanks for your reply.

So this means I can lightbake a static mesh with, let’s say a 512 res and afterwards create a 64 res from that, just for my LOD02, all without affecting the baked texture, or the need to rebuild the lighting?

If so, does it only happen on pressing the “Apply Changes” button, or as well on pressing “Save”?

thanks!

4

Not really. While the Build settings appear in each LOD they will use the originals layout and not use different LM textures.

You can use the Build Settings to set the size you want the LM resolution. This will simply space the UV islands apart enough so that it reduces the light bleed between islands and repacks them. This does not mean that you will have that size LM when you hit the apply button. This will need to be set in the Lightmap Resolution section under Static Mesh Settings. If you’re planning on using a 512 LM resolution it would be best to set that in the Build Settings as well so that it gets repacked and spaced properly.

Anytime the Build Settings or the LM resolution is set in the Static Mesh Settings tab this will cause the Lightmap to be wiped and you will need to rebuild lighting.

5

Hello Tim, thanks for the explanation.

  1. Now I’m just wondering, as an example, when it comes to that LOD2 or LOD3, since there’s only one Lightmap Resolution setting for the whole thing, is UE creating a 512 for every LODs? Even thought we’d be looking at a mipmap a certain distance (hence LOD).

  2. For the Build settings/LM resolution; should I considering halving the resolution/padding settings at every LODs? It seems to get rid of artifacts. But it’s not reducing the actual lightmap texture resolution right?