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UV channel 0 disappear when exporting to .fbx and reimporting the .fbx

To reproduce this bug:

1) Open desertrallyrace sample project (get it from the marketplace)

2) Export the following mesh: Game/Assets/Meshes/SM_PalmTree_01 to .fbx

3) Import the .fbx to your project

4) Open the mesh in the ue4 mesh editor and toggle display of uv's

you see that the channel 0 is now empty, and the channel 1 for lightmap is still here

Any solution to get this uv channel 0 back? :/

And if you open the .fbx file in 3dsmax, you can unwrap uvw the mesh and you will see that the channel is here so, the channel is still ok when exporting but when we reimport the .fbx the channel 0 just disappear !

is the 2014 fbx format concerned in this bug? :o


Product Version: Not Selected
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asked Jun 05 '14 at 05:23 PM in Bug Reports

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Hi skeleton60 -

The particular mesh you were looking at was actually generated in Speed tree and has a total of 4 UV channels, UV 3 and 4 are not used in UE4 but are used in the Speed tree software.

For what you are trying to do there is a fix, when you open the exported FBX in Max, add a UVW Mapping Clear modifier to the Palm Tree and choose Channel 3 and add another one for Channel 4. Collapse all and export as the FBX again.

When you import the tree it should all be fixed with only 2 UV Channels and the texture and lightmap channels correctly laid out.

Thank You

Eric Ketchum

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answered Jun 05 '14 at 08:43 PM

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Lovecraft_K ♦♦ STAFF
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avatar image Lovecraft_K ♦♦ STAFF Jun 05 '14 at 09:16 PM

Do you open Map Channel 1 in Max and see if the unwrap is as expected?

I would start from strach and export the original mesh again, import into Max, clear those two channels out, then Collapse you stack, the add an Unwrap UVW modifier, open the UV editor ensure that Map Channel 1 is correct, collapse the stack again add another Unwrap UVW modifier, change Channel to 2, Abandon changes and open UV editor and ensure Lightmap unwrap is correct. Finally collapse stack and reexport and import into editor.

Make sure you are import the mesh as a new asset and not trying to replace existing.

Eric Ketchum

avatar image skeleton60 Jun 05 '14 at 09:23 PM

Thank you i did a mistake with 3dsmax trying to do your solution :)

Staff do an epic job here :)

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