Hi, I'm trying to use Kyle's root.xsi shipped with the jk2 SDK to do some animating / weighting in Softimage Mod Tool. Problem is, there's no face bone in it, but the _humanoid.gla clearly uses it. So I wanted to add it myself, but I'm not completely certain how it's supposed to be in order to a) make new animations work with the existing weighted models, and b) make the old animations work with new models weighted to the modified skeleton.
From what I can see in Modiew it seems the face bone is rooted at the cranium and has the same orientation and starting point as it; that would imply the cranium's length is zero, wouldn't it? But at the same time in the root.xsi the cranium has length 4 and the face bone just isn't there. Now there a two possibilities that I can think of, and I'm not sure which way to go:
1.) cranium's length = 4, face bone's length = 0 (virtually).
2.) cranium's length = 0, face bone's length = 4.

Can anyone shed some light on the matter? Thanks.

The face bone doesnt really exist, it's more of a group of bones that is created at compiling stage (could be way the GLA handles the face hierarchy?), that is based on what i see in max and the compiling log.

This is what the compiling log shows:
Bone 15: "cranium":
Parent: "cervical" (index 14)
#Kids: 1
Child 0: (index 52), name "face"

the #kids:1 of the cranium is the "face" group, yet it doesnt exist in the skeleton.

So ignore the face bone...even the bones extracted from the JA .GLA didnt have a face bone, still shows up everytime a root is compiled. Carcass will do its magic.

Ah, thanks a lot for the answer. Does that mean I should go with 1.), or should I just leave the face bone out completely? Well, I'll try the latter and see if the gla spit out by carcass can still be merged with _humanoid.gla, though I suspect it can't.

You'll have more chances of having a bones mismatch by adding anything that is not present in the default skeleton that comes with the SDK.