Fix and reset your Mixamo avatar rig

The Mission

Creating avatars is really fun, all that 3D modelling can be very fulfilling, I know.
But after the fun part, comes the technical one, rigging.
On this post we'll explain how to use Mixamo to rig your characters in no time, and also solutions for some troubles you'll find along the way.

Resources

• Mixamo
• MayaLT 2019 or your preferred 3D software

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Rigging our character in Mixamo

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Mixamo is an automatic rigging website tool that allows you to create quick humanoid for free.
​As long their shapes are not complicated.
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If you are already familiar with this tool you can skip to the next part.
To log in you can use your Google Account.

Mixamo

Upload your character

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Once you are logged in, press Upload Character and then drag the FBX you want to rig.
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Note that the FBX file preferably should be in a 2013 or earlier, to avoid errors from Mixamo.
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Make sure to orient the model to have the front face looking forward.

Bone structure

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After that it will ask you to indicate different parts of the body on top of the model.
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You also can choose the Skeleton LOD according how many fingers of the hand do you want your character to be able to move.

For a VRChat avatar you want to use at least 3 Chain Fingers because is the minimum that the game needs to detect correctly all the basic movement of your hand.
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If Mixamo doesn't detect 3 "fingers" it will create less chains and you will have issues later.
Once everything is placed correctly just click Next and the autorigger will do his work. If you are satisfied with the result, click Next again. Now you can see the character in different animations to ensure the quality of the rig.

Don't trust, test

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Before downloading your character from Mixamo, we strongly encourage you to run the following animations to test if there is going to be any problem with the avatar beforehand. Some of these problems can be solved after downloading the rig, but others cannot.

Skinning test makes you character make really exaggerated poses. Perfect to see if there could be any skin problem beforehand.

Typing is really useful if you want to check if your avatar has all the fingers rigged, since it moves all the fingers individually you can see if there are any issues.

Download that avatar!

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If everything looks alright to you, go ahead and press Download and choose T-Pose and fbx.
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Remember to not have any animation loaded in right panel, this could modify the pose of our rigged character.

Having trouble yet?

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Mixamo's automatic skinning and rigging can work. But more often than not, your characters will encounter different problems that only can be fixed manually using a 3D software.
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What went wrong? What do I do? These are questions that I made myself while working on these characters and I hope I can answer them here. Not all models are the same. Some have special characteristics and you have to look out for those.
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These next examples will help you to identify and fix problems that could happen.

Bone influences

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At first glance, this Hot Dog boy looks normal. It is in T-pose and it's completely rigged and skinned. Yet, there are some problems that we need to look out to.

It wasn't until we tried it on VRChat that we saw the problem. As I said, we all lost valuable time for not checking the rig and skin.
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Seriously, check what's given to you. Make sure everything is okay.

Mixamo places a shoulder bone between the Upper arm and the Spine 2 bone. This bone doesn't usually move around much, but Mixamo still puts influence, leaving some nasty results, like this one.
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Lifting up 30º the right shoulder leaves us with an horrible looking deformation.

This is the kind of stuff we should be aware of. For this particular case, removing all the influence of the shoulder bone will be enough to lead to some better results.
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Removing all the influence sometimes is not the best idea so you can also reduce the amount of influence the shoulder makes on that part of the body for different results.
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In this pictures you can see how the bone influence should look for both cases.

Influence removed

Influence decreased

Visemes issues

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One particularly annoying problem that I personally found while making visemes for the avatars with Maya LT, was that even when the character was in T pose, if I tried using the blend shapes, the model will return to its original pose before the rigging. You can check what I'm talking about on the gif below.

To fix this we'll reset our character rig.
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First, we will duplicate our original character.

Now bind the new mesh to the bone chain we have.

If an error occurs, right click on the Outliner and uncheck the "Show DAG Objects Only".
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Scroll down until you see bindPose1.
Delete that, and repeat the bind.

Select the old mesh, then the new one. Go to Skin > Copy Skin Weights.
You can delete the old mesh, since it has no use.

Now all the blend shapes will work perfectly!

Conclusion

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Like any automatic tool, Mixamo is a great time cutter that provides an easy way to go with decent results, but problems can arise, we covered some of the most annoying ones and hopefully this blog post helped you somehow.

Post by:

Pedro @05predo

Pedro Solans was an intern and now junior animator working at Polygonal Mind's in-house team.
Animation film lover, Tekken player and animal huger .

Daniel @toxsam

Daniel García (aka Toxsam) is the founder and creative director at Polygonal Mind.
In love with videogames since he can remember, passionate about geometry,
​VR addict and energetic persona.