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Questions about lightmap settings.

Lightmapping in UE4 isn't completely clear to me, so i hope someone can clear things up for me.

When i open up an asset (mesh), i get two resolution settings for lightmap ''Min lightmap res'' and ''lightmap'' res. what is the difference between the two and why are they set to 64? isn't 64 exrtemely low. I never change ''min lightmap res'' but only ''lightmap res'' and change it between 256 -1024 (depending on how big and important the asset is). am i doing this right or do i have to change ''min lightmap res'' aswell to get better quality?

Sometimes i also get blocky shadows on my walls, is this because a resolution of 1024 for a wall is too low? I see a lot of people using 128 to 256 resolutions for scenes and getting really great bakes, how does this happen with such a low resolution and does this have to do with the lightmass settings within the world settings tab and not with the resolution?

And what setting does the ''override lightmap res'' actually override, is it the min lightmap res or the other. it's so confusing to me.

I hope these questions are clear enough to be answered. any help would appreciated.

Product Version: UE 4.13
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asked Jan 24 '17 at 12:59 PM in Rendering

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2 answers: sort voted first

When you let ue4 re-create or auto generate the lightmaps, it will look at the minimum lightmap size and add spacing between UV-clusters/islands and edges of the 0-1 space according to it. So if your minimum is "64" but your regular lightmap resolution ends up being "512" it will mean that there will be (at least) 8 pixels of wasted space between your uv-clusters/islands and the edges of the 0-1 space.

This is why --when auto generated/restructuring existing lightmap uv's-- its important to set the minimum lightmap resolution properly.

the way your uv-map is laid out, how stretched/warped your uv-island/cluster is, the lighting/shadow/compression/settings all are influencing the quality of your lightmaps.

The override lightmap res. overrides the regular lightmap resolution, and not the min. lightmap res. one.

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answered Jan 24 '17 at 01:29 PM

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avatar image PotatoShield Jan 24 '17 at 02:39 PM

so if my LM res is 1024 what should my min LM res be for example? or doesn't it really matter all that much?

avatar image Luos Jan 24 '17 at 03:09 PM

If you are sure it wont be lower, it should be identical. But only if you are generating or re-allocating lightmap uv's automatically by ue4. else it doesn't matter.

If you are auto generating/reallocating lightmaps, and you keep it a 64, while the min lightmap is 64, you are losing hundreds.. if not more perfectly good pixels that could have been used for lightmap baking.

avatar image PotatoShield Jan 25 '17 at 07:57 AM

I'm creating my own lightmaps in 3ds max, so i guess i don't have to take that into account. thanks for your answers

avatar image Luos Jan 25 '17 at 11:03 AM

be sure to set the answer as "accepted" btw :)

additionally, even though you are doing the lightmaps in max, keep a minimum lightmap size in the back of your head. that way you can be sure you arent wasting the space between uv-islands :)

avatar image PotatoShield Jan 26 '17 at 07:08 AM

Thanks i'll keep this in mind.

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the "min lightmap resolution" is under "build settings", it's used in case you wan't to generate a new UV map to your mesh (it's usually used in case your UV overlaps, so you will need another UV for the lightmap), unless you generate a new lightmap it will have no effect, the lightmap resolution is the the actual resolution, is 64 extremely slow? it deppends on the size of your mesh and in it's kinda personal too, if you notice there are some "shadowed squares" on your mesh it maybe caused by low lightmap resolution, also the bigger the resolution, more memory it will take. i use resolution of 16 for some meshes, and it's okay. about the override lightmap resolution it will override the lightmap resolution (not the min) for that specific instance of the mesh in scene, in case you need a better looking lighting for that specific area in the scene.

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answered Jan 24 '17 at 01:46 PM

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