Rigging, 3DSMax: Fixing negative scale on bone?


I posted this up in the Max forum, but I figured it couldn’t hurt to drop it here, too.

I ran into this problem after modelling a quickie character in Wings to test out some rigging in MAX to then be brought into MotionBuilder. Big problem, though, is that I mirrored the left arm chain and leg chain in order to create the right arm and leg, and I hadn’t realized that the mirror process simply set the scale of the parent bone to -100%. Kind of lame, now that I’ve gone to all the trouble of painstakingly skinning the bastard.

Now, bearing in mind that I’ve gone through the documentation and tutorials, as well as done some rudimentary searches online, I can’t for the life of me figure out whether or not it is possible to reset the scaling to a positive value of 100%, while keeping the bone chain in the same position. The closest analogy I can think of is the “Transform Permanently” (or something) command in UnrealEd, which simply zeroes out all transformation values while keeping the new position.

(The MB VTMs mentioned this problem, but only gave a solution for Maya users in the form of a MEL command)


the way you fix this in maya is after you mirror the skeleton…you create new joints that you point snap on top of the mirrored half…and then delete the bones with the negative scale.


Hmm. I reckon I should be able to do that in Max. However, is there any other way to fix this issue, since I’ve already assigned the weighting to the skin modifier? Thanks.


they way to solve your second problem would be to import/export the skinweights or copy/paste them…i dont know max well enough but can tell you how in maya.

the 2nd way…a bit more painful though…is to manually change the rotational axis of each joint.

btw: is it actually a problem with the negative scale on the joints?

If everything works…why fix it?


I think I should be able to figure out how to export and re-import the skinweights, although I was hoping it wouldn’t have to come to that. :hmm:

manually change the rotational axis of each joint.

Ouch, that does sound painful. I’ll take a look at that, though, thanks.

btw: is it actually a problem with the negative scale on the joints?

If everything works…why fix it?

Actually, MotionBuilder apparenly doesn’t like negative scaling on joints, from what I’ve read (and heard, on the 3DBuzz VTMs), hence my trepidation upon finding out about the two negatively-scaled joints in my skeleton (didn’t realize it until an error message popped up when trying to export to .FBX).


if u have only 2 joints that r negative scaled…it should only take a couple minutes to correct the rotations no?


You CAN’T mirror bones using mirror option in max. I don’t rememer now if it’s in MAX 5 or I downloaded it from somewhere, but there’s a script called mirror bones :). Use it. It mirrors bones, but do not prefrorm negative scaling.


Is this max 5? Have you tried the Re-align button on the Bone Tools rollout?


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