UDK skeleton for Mixamo characters
This page is for people who are new to UDK, and wondering how to put a UDK compatible skeleton inside other character meshes.

Background

When I first started UDK not too long ago, I wanted to use some characters that were more normal than the provided "UT3_Male" and "UT3_Female". I thought I could just look around for some public domain character meshes, then bind the mesh onto the ExampleSkeleton.fbx from the official UDK guide. Then I would be able to use the UDK provided character animations, while using a nicer looking character.

Turns out, this was a much more complicated thing to do than I had anticipated. First of all, Mixamo delivers its chars by default in the Maya/blender standard "T post" stance. UDK does not. Then Maya was not cooperating, because as I later discovered, there was a magic setting that needed to be tweaked.

Details

Here's specific details on how to make it all come together, with a bias towards Maya.

Grab the resources

  1. Download a character from Mixamo. They have both for-fee ones, and free ones
  2. Download the modified skeleton, ut3_skele_for_mixamo.fbx or use maya scene instead: UT3_skele_for_mixamo.mb
FYI, I changed the UDK skeleton for the most part by simply setting rotations to 0 degrees. The fingers were more difficult, however.

Bind the two together

You next have to merge them together in some third-party program.

I have Maya, so that's what I'll describe.
(Random tip: You may want to set Display->Animation->Joint Size=0.5 or smaller)

It's fairly easy, once you know how:

  1. Import one of the files you downloaded, and then the other one.
  2. Delete any additional bones that came with the new character.
  3. Scale the character mesh, aka "skin" to the skeleton size. In maya, you can probably take a shortcut of selecting the mesh, then use either the channel box area, or the attributes area, to set the Scale (X/Y/Z) to be 0.53 (warning: if mesh has any non-zero Translation attributes, you will have problems)
  4. Bind the charcter "skin" to the skeleton. In Maya this is done as follows:
    1. Select the mesh AND the skeleton this time.
    2. Skin->Bind->Smooth Bind[]
    3. (This should have brought up the Smooth Bind Options window)
    4. Make sure "Max influences" is 3 or smaller!
  5. (Make sure you are in full render mode in your window, not wireframe, then) export what you have as a new .FBX file
That's pretty much it. You should be able to now pull up UDK, then use the "import" button at the bottom of the Content Browser, to import the file just saved.

Tip: When you import into UDK, I suggest you choose a "grouping" name that is unique to the char you are importing. Then UNcheck
Options ->Materials -> Create Groups Automatically[]
That way, all textures pulled in with the character, will remain in its own subsection. This eliminates any chance of overwriting something from another area in your assets.
If you did everything right, then your import created(amoung other things) a new Skeletal Mesh asset. Double-clicking on it should bring up the AnimSet Editor window. If you then choose one of the standard Anim(ation) sets under (Anim tab)->AnimSet_ pulldown, such as K_AnimHuman_BaseMale, you should then see your character change its pose. You can then click on any of the entries in the previously blank "Animation Sequences" area, to see it change poses some more.

Disclaimers:

Please note, that I do not claim to be a great 3d artist, or animator, or...
So, the skeleton provided is not perfect. Particularly the fingers. But hopefully, it should help you along your own journey. If you happen to work with it and make an even better tuned one, please let me know! I'd be happy to reference it and give you credit.

Written by:Philip Brown
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