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Can't have a clean FBX import from Mixamo website (UE4 auto-rigged Fuse characters)
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Description

System Information
OS: Windows 8.1 64bits
GC: nVidia GTX880M

Blender Version
Broken: 2.72, 2.73 and 2.74-rc
Worked: none

Short description of error
Context: The FBX is provided by Mixamo website (download of my auto-rigged characters with UE4 skeleton). If I import directly the FBX into UE4, I have no problem at all. When I try to import it into Blender, the problems described below occur, depending on the Blender version.

2.72: imported parts have no parents, all vertex groups are lost, the mesh is altered
2.73: the mesh is altered (fingers and sandals)
2.74-rc: all vertex groups are lost

Exact steps for others to reproduce the error
Import -> FBX -> File below

What I meant by altered mesh:

The FBX file:

Please tell me if you need more info, thanks a lot in advance!

Event Timeline

Samuel P. (S4M) raised the priority of this task from to 90.
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Samuel P. (S4M) added a project: BF Blender.
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There were a few changes made for FBX, so you may have to change some settings here. But we need Bastien to tell us more!

The report re 2.74-rc1 was a bug also reported in T43979, just fixed it in rBAe716a3503d0e.

So we are back to 2.73, i.e. odd tip of fingers. Investigating...

Bastien Montagne (mont29) lowered the priority of this task from 90 to 30.Mar 14 2015, 12:23 PM

OK, so issue comes from missing vertices in figertips’ vgroups.

I could try to dive into that *huge* FBX file and check whether it is "corrupted" or not, but this is highly probable (since all other vgroups import OK afaik), and it would take a huge amount of time.

Can you please double check org char is fully and correctly weighted in those areas (finger tips)?

Note UE4 may do some kind of 'auto-weighting' or so in those cases? don’t know…

Thanks for your quick reply!

Unfortunately, I have no control over the creation of this FBX. I use Mixamo Fuse v1.3 as my character creation platform, with an Indie license. The meshes are uploaded and auto-rigged on their server, and then I can download the UE4 version of it. I really need the ability to edit the models between Mixamo and UE4 in my workflow (to reduce polygons, separate parts, add APEX clothing and so on). So if I can run some tests for you, please ask.

In case it helps, here is a lighter naked version of the same character:

And for comparison, this is the collada version from Mixamo website. It works just fine (but it's not a UE4 skeleton, so I can't use it).

When importing into UE4, warnings are displayed whenever the engine has to perform some automatic corrections. If I export the above FBX from Blender, this is what I receive:


I don't have these warnings when importing the original FBX file from Mixamo, so I assumed Blender was doing something wrong.

Just wanted to add that I don't have this mesh alteration on the 2.74-rc. So if the vertex groups will be correctly imported in the next version, it should be all good for me. Not sure it's worth spending too much time on it, if it's going to be fixed soon.

Yeah, UE4 errors are exact same as what you experience in Blender - some vertices not weighted (assigned) to any bone of the armature. Will try to see what's happening exactly here.

In the mean while, please note that it's pretty easy to fix the issue in Blender - just select a finger tip vgroup, switch to wpaint mode, and 'correct' missing assignments (blue areas in the middle of red one).

Thank you, that's really good to know!

Bastien Montagne (mont29) changed the task status from Unknown Status to Archived.Mar 15 2015, 12:57 PM

OK, so I check that file, and indeed, it has some vertices assigned to their bones with weights like 0.000001 and such. This cannot work at all, I’m not sure how UE4 handles that, but in Blender this is considered broken data that has to be fixed by hand.

So thanks for the report, but there is no bug here in Blender importer. I’d really recommend submitting a bug report to the tool generating such invalid skinning data…

But in that case, why can the 2.74-rc version import the mesh correctly, with no visible glitches? (just the vertex groups lost)

For UE4, probably if the value isn't missing, even close to zero, it doesn't raise a warning and maybe perform some adjustments when importing.

In any case, thanks for taking the time to check the file. And indeed, I'm going to follow up with Mixamo.

In 2.74-rc1, there was a bug in importer which would abort any skinning between armature and mesh (see T43979, fixed it in rBAe716a3503d0e).

Btw, do not hesitate to followup here exchanges with Mixamo. :)

I understand now for 2.74-rc and the lost vertex groups, it makes sense.

I opened a ticket at Mixamo, and will keep you informed.

Thanks again!