UV issues

Development Rendering
1

so im used to doubling down on UV’s in order to save a little space, unreal4 obviously is not a fan of this, so i tried just creating a second UV and still no luck, ideas? or what am i doing wrong im getting a 73% overlap even running multiple UV’s on the same model.

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2

Hi,

After you have crfeate your second non overlapping UV channel and reimport the mesh, you need to set the lightmap channel index to the new UV map.
When you imported the mesh with just one channel, the lightmap is set to that channel.
Unfortunately the importer does not recognize that there is now an additional UV channel.
Set the value in the mesh editor details panel.
When you import a mesh with two UV sets, the importer automatically sets the second as lightmap index, but not in this reimport scenario…

Cheers,
Klaus

Cheers,
klaus

3

Also, make sure your lightmap resolution is set correctly, by default it’s 32

4

yea i usually put the lightmap res to 64, or what would you recommend? Also thank both you for the quick reply.

5

That depends on the model/level.
I sometimes use 512 … :cool:

6

Hi,

There are a couple of things here to try.

  1. When you created your second UV channel did you just make a copy of your first UV channel or did you do a new layout.

If you did a new layout, this should be all that is needed. If you only made a copy, it’s still going to give you the overlap errors because the lightmap should have no overlapping UVs. This is because shadow information is getting baked into a texture. If there are overlapping UVs it will bake the shadow on multiple faces where it’s not needed.

  1. When you created the second UV did you create this from the in-editor auto-generate UVs tool or did you create this in your modeling software?
    a) If you created in your modeling software did you use the “reimport” option
    b) Did you delete your old mesh and import fresh?

If A) open your mesh in the mesh viewer/editor and under the details panel to the right find “Lightmap coordinate Index” and make sure this is now set from 0 to 1. Using the auto-generate tool will not change to the correct channel automatically.
If B) Open your mesh in the mesh viewer/editor and select the tab at the top that says UV and click it. Change the UV channel drop down from 0 to 1 to view your layout. Make sure this looks correct.

If neither of these help can you post a screen shot of your First UV layout for textures and your second UV layout for lightmaps?

Thank you!

Tim