When exporting static meshes with bExportSourceMesh enabled, there is a problem where all UVs are fragmented.

Development Pipeline & Plugins
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1

Hello.

In the StaticMesh Export option, when bExportSourceMesh is set to True, exporting StaticMesh Assets and importing them into DDC tools such as 3dsMax or Maya results in the UVs being imported in a fragmented state.

I have attached detailed reproduction steps separately.

Are there any git commit fixes or reported cases regarding this issue?

Thank you for your attention.

Thank you.

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2

Hello,

Thank you for reaching out.

Would you be able to provide the repro steps here? I can’t seem to find them even though you mentioned it would be attached separately. All I see attached is an fbx file SM_Teapot.

Thank you in advance!

Regards

3

Hello,

How was the static mesh asset created in the Unreal editor?

How do the UVs look like in the static mesh editor?

Thanks

Regards

4

Hi,

You answered my question. Thanks.

I just wanted to know whether the asset was the result of an import or not. If so, which format.

And, if I understood well, the attached FBX is from 3ds max. Right?

Regards

Jean-Luc

5

Hello,

This is a bug. Sorry for the inconvenience.

It looks like you are the first to report this issue.

I opened a bug that we will look into in a future release. Here is a link to the bug: UE-330931.

Note that it may take a couple of days before the link becomes operational.

Thanks for your patience.

Regards,

Jean-Luc

6

Hello.

I apologize for the omission of the reproduction steps. I will now explain how to reproduce this issue.

1. Import the attached SM_Teapot into Unreal Engine.

2. Then, export it as a Static Mesh. Check the “Export Source Mesh” option before exporting.

3. When you import this FBX file into 3ds Max or Maya, you will see the UVs are fragmented.

4. Export the same asset again, but this time uncheck the “Export Source Mesh” option before exporting.

5. When you import this FBX file into 3ds Max or Maya, you will see the UVs remain intact, just as they were originally created in the DDC tool.

Thank you !

Regards

7

Thank you for the additional information.

I was able to recreate what you were seeing, after disabling nanite in Unreal on the static mesh.

From my understanding, this may be a limitation rather than a bug due to unreal converting and processing the file to suit unreal’s structure during import which may fracture it.

Then on export, having Export Source Mesh disabled utilizes the rendered mesh, which has been merged, welded and optimized.

That being said, it is my conjecture / interpretation and to get clarity on this I went ahead and passed on a question to Epic to see if this is a bug or limitation.

If it is a bug, I’ll go ahead and make a bug report and link it here in this discussion.

Thank you for your patience.

8

Hello.

Thank you for taking the time to listen to my question.

I understand the points you shared, and I appreciate your interest.

One thing I’d like to cautiously add is that I’m experiencing this issue regardless of whether Nanite is enabled, as long as bSourceMeshExport is checked.

The same problem occurs even when Nanite is activated.

Thank you again!

9

Hello,​

​

I did not fully understand the question “How was the static mesh asset created in the Unreal editor?”

​

I created the mesh in an external DDC tool (3ds Max) and then imported it.

​

I have attached the static mesh .fbx file.

​

I have attached images showing the UVs for the original mesh in 3ds Max and Unreal Engine.

​

Thank you for your interest.

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10

Hello,

Yes, that’s correct. I created it in 3ds Max, exported it from 3ds Max, and then imported it into Unreal Engine.

Thanks