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What does this 'Lighting Build' error report mean?

alt text

So my 'Humvee' asset keeps getting this error report every time I do a 'Lighting Build'. So, what does this mean and how can I fix it?

Anyone know?

Thanks! :)

Product Version: UE 4.9
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asked Apr 24 '16 at 09:35 PM in Using UE4

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avatar image sayer6913 Apr 25 '16 at 06:20 PM

Does anyone know?

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This means your mesh's lightmap UVs have multiple UVs in the same place which breaks lightmapping since different lighting will try to be in the same place. This may be because you're using the wrong UV set. Most meshes want to use UV channel 1 and not 0 so make sure you have the right channel set in your static mesh settings. If your UVs in channel 1 are overlapping you can generate UVs for lightmapping whic is also in static mesh settings. Make sure the UV channel you're generating into is the same as the UV channel you're using for lightmaps.

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answered Apr 25 '16 at 06:27 PM

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avatar image sayer6913 Apr 25 '16 at 08:04 PM

Ok, thanks for the reply! Also, so this doesn't mean I have to unwrap my model over again right? It just means I need to fix my UV Channels?

avatar image QSBen Apr 25 '16 at 08:37 PM

Correct, you shouldn't have to re-unwrap your model. generating lightmap UVs basically does that for you if you decide to use it.

avatar image sayer6913 Apr 25 '16 at 10:01 PM

Ok, one more quick question. Would I change the UV channel in UE4 or the software I built the model in which is 3DS Max?

avatar image QSBen Apr 25 '16 at 10:07 PM

You can do either but it is easier to just use "generate lightmap UVs" in your static mesh settings. This setting will do automatic unwrapping for you which should work just fine for lightmaps so you don't need to do it yourself.

avatar image sayer6913 Apr 26 '16 at 06:59 PM

I put on UV Channel 1 and it keeps going back to channel 0 when I exit the page. Why is this?

avatar image Wyatt Grit Apr 26 '16 at 07:52 PM

With the Asset window open, top right corner in the "Details" panel, Click on the eye and with a down arrow and Activate "Show All Advanced Details". Scroll Down to static mesh settings, you should see "Light map Coordinate Index". Set it back to Zero. Then save the changes.

avatar image sayer6913 Apr 27 '16 at 02:21 AM

Sorry it still keeps doing it. Any videos you know that may help? Thanks!

avatar image Wyatt Grit Apr 27 '16 at 02:24 PM

After setting it back to Zero, close the file completely, while saving new and modified assets. Reopen and it should have registered the changes.

Sometimes new assets only properly update after the main file has been closed .

avatar image sayer6913 Apr 28 '16 at 05:12 AM

I tried that and it still keeps resetting back to UV Channel 0. Sorry I'm such a pain to help I don't get why it keeps resetting

avatar image Wyatt Grit Apr 28 '16 at 09:00 AM

Oh sorry I misunderstood. Why Channel 1? UV Channel 0 is the original imported UV. Channel 1 is the light map generated by UE4. If you want/need Channel 1 then it should let you keep it if you follow my previous instructions and set the "Light map Coordinate Index" to 1 instead of default 0.

avatar image QSBen Apr 28 '16 at 05:27 PM

I ran into this same issue. I fixed it by increasing the lightmap resolution. When at a resolution of 4 it doesn't seem to actually generate new UVs so there were none in channel 1 and it would always reset to zero. So increase the lightmap resolution in the LOD settings and Apply Changes, then you can check the UV set by switching UV channels in the toolbar and hitting the UVs button to view.

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