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Mixamo -> Blender -> UE4 workflow issue

Hi there,

As a last resort, I’m posting here to find a solution to my problem… I’ve been struggling on this for a long time now (since January). I can’t seem to find anyone else having this problem, and I can’t postpone anymore the resolution of this issue. Maybe someone in this wide community knows something about it, I really hope!

So, a bit of context first. I’m not a 3D artist, that’s why I use Mixamo services (with which I’m so disappointed… but that’s not the point), and that’s why I use Blender (can’t afford to spend thousands of Euros every year into an Autodesk software just to perform very basic operations such as separating meshes, removing some vertices, etc.).

My workflow to produce skeletal meshes is the following:

  • I use Mixamo Fuse as my character creation platform
  • I auto-rig the mesh on Mixamo Web portal
  • I export the rigged character as FBX with UE4 skeleton
  • I import the FBX into Blender
  • I export the FBX from Blender after a few very basic modifications
  • Finally I import the resulting skeletal mesh into UE4

The workflow works great with Fuse female-based characters. No issue so far.

The problem occurs with male characters. The FBX file generated by Mixamo for this type of characters contains very low weight values (fingers and toes). For some reasons, UE4 and Autodesk softwares import just fine the FBX, while Blender is discarding or setting to zero those very low values.

At first, I thought it was a Blender bug, so I opened a ticket you can read here: ⚓ T43992 Can't have a clean FBX import from Mixamo website (UE4 auto-rigged Fuse characters)
The Blender developers position was clear: these values are unusually low and Blender will not change the way it manages this type of data. Meaning: no solution on Blender side, other than fixing the weights manually.

Then I opened a ticket at Mixamo. The last words from their support was: “For the moment I’ve let the engineers know about the fingertip issue - I believe it has to do with the way we remove the end bones of the fingers (length bones) which the UE4 skeleton doesn’t use. Should be relatively easy to fix, however our engineer responsible for that is out of town today at a conference. I’ll send you a notification as soon as we have the fixed UE4 download and we’ll keep working on better Collada/Blender support.”.

This was last March… So, with the recent Adobe acquisition of Mixamo, and considering I’m the only one (it seems) having this issue, I have to find my way out of this mess and move forward.

The only solution I know is fixing manually the weights in Blender. I gave it a try last week and I had 2 major problems: finding all the affected vertices (after spending half a day on 1 model, couldn’t find them all…), and the (in)accuracy of this manual weighting (not sure how it’s going to affect the quality of the importation into UE4 afterwards).

Now my questions.

  • Am I really the only one having this workflow and this issue? Or did I miss something?
  • Can you think of an other solution? Maybe a software I don’t know about that could fix the FBX values before importing into Blender?
  • If fixing this manually is the way to go, any tip to automate this a bit? Ideally, a software or plugin to find all the affected vertices, and maybe even set some consistent values.
  • Auto-weighting in Blender fixes the problem, but the weighting is very different, compared to the female character. If I go that way, how is it going to affect the skeletal mesh once imported into UE4? Is it going to respond identically to animations? Is the generated physical asset going to be the same? Etc.

Sorry for the long post, and thanks a lot in advance for your answer. I really need fresh eyes on this issue!

I have the exact same problem, I manually weight the vertices on the fingertips and toes, I assumed mixamo knew about this and are going to fix it in the future - I really hope they do.

Ah! A fellow old school DnB fan? xD

Happy to know I’m not the only one having this issue… How do you find all the vertices? I spent hours in Blender hunting for weird shapes around fingertips and toes, and still got 1 error while importing into UE4. Do you have any tip here? Thank you for your reply!

Hi again, PhoTek - this is Jeanette the support engineer from Mixamo who talked to you. I just wanted to let you know that this issue has not been forgotten. As you can imagine it’s been a hectic couple of months but I have it logged with our engineering department, but as you imagine, there have been some shifts as we are settling into Adobe.

I’ve been working yesterday at defining a reliable and time-efficient method to fix these damned vertices. The goal was to avoid using the weighting tool, to be sure there are no vertices left unweighted when it’s done and to have a consistent result if you’re going to repeat this for a lot of characters (my case…).

So just for the record, here is my method:

  1. Make sure all vertices in group have a weight.
    Select the “Body” part of the mesh, enter edit mode and click on the data panel.
    Under “Vertex Groups”, click on Weight and enter “0.1”. For each of the 12 problematic vertex groups, meaning toes (ball_l and ball_r) and fingertips (thumb_03_l, thumb_03_r, index_03_l, etc.), force the weight by re-assigning the vertices. This is done by clicking “Select”, “Assign” and “Deselect”.
    You should now have a 0.1 weight on all vertices in these groups. You could already import the mesh into UE4 without any warning if you’re in a hurry (in that case, you might want to force the weights to 1 instead).

  2. Clean up the vertex groups.
    This is optional, but let’s be honest, some groups are a real mess… Toes have most of the leg assigned, and even vertices from the other leg… Not sure what are the consequences afterwards in UE4 for keeping such a bad weighting.
    For time-efficiency, I perform 2 and 3 for each vertex group (takes time to move the camera for a Blender newbie ^^).
    Again, having the “body” part of the mesh selected in edit mode in the data panel, select one of the problematic group.
    Switch to “Wireframe” display for faster selection.
    Click “Select” in the data panel.
    Place the camera above the mesh part, and with ctrl+shift+lmb (maintain and draw the area), select the vertices you want to keep. You should now have only the unwanted vertices selected, so click on “Remove” (data panel).
    Move the mouse cursor in the 3D view and click on “A” to deselect the vertices.

  3. Weighting the main area.
    As I said, same setup as previous step (body selected, edit mode, wireframe).
    Make sure you have Weight set to 1 under Vertex Groups in the data panel. Click “Select”.
    With ctrl+shift+lmb, select the vertices that are not part of the main area. You should have now only the main area selected, press “Assign” then “Deselect”.
    Repeat for all 12 problematic vertex groups.

Cheers

Thank you so much for this fix! But I’m still having an issue. When I put the .FBX file generated by Mixamo into UE4 all animations work fine. But when I import it and edit things in Blender, export it as .FBX and import it in UE4 all my animations fail to import. Do I need to change something in the animation’s .FBX files too after editing the mesh?

Exporting fbx AScii format from blender fixes the issue

This is what I do. I import the mesh into UE with no skeleton. It builds it from the one already there. Then I re-target it with the humanoid rig. I don’t have any issues in blender after that. Of course I do not do 3D if I don’t have to. I am a programmer so I could be naive.

This actually didn’t work for me.
This problem is still there after many years.