View Full Version : blendshapes for joint deformation in MB?

07 July 2003, 03:03 PM
I like to use blendshapes in Maya for joint deformation instead of painting skin weights. I then use set driven key with the joints driving the blendshapes to automate the deformations. This is the process I usually use:

Motionbuilder doesn't support wrap deformers, but I know it supports blendshapes. But I have only seen it used with the "character face" attributes. Is there a way to wire the blendshapes to the joint rotations in Motionbuilder? Or is there any type of set driven key? If so, please let me know how to do it.

07 July 2003, 11:23 PM
I have also wondered about this. Perhaps using a relations contraint somehow?

07 July 2003, 08:56 PM
er.. why would u need to do that blendshape/setdrivenkey stuff to get correct deformation in MB. MB is only for animation, you can go with just standins or with an ok weight job, and after that you'll be sending the animation data back to maya. You should setup the blendshape/setdriven key stuff in maya, and just import the animation done in MB.

07 July 2003, 09:23 PM
The reason, for me anyway, is since MB is used for animation and thus performance, I'd like to see the complete performance as closely as possible in MB, so I have no suprises once I get back to LW, or Maya...

If weighting is an approximation, you might get undesired results in the final animation.

07 July 2003, 08:41 AM
Hi lfgabel, are you after something like this :

The bulge is a morph driven by the rotation of the joint..


07 July 2003, 08:49 AM
yes, that's similar to what I'm talking about. But the thread is in regard to doing this in MB as well so there are no suprises at the rendering stage back in LW.

07 July 2003, 09:06 AM
Yeah, that .gif is straight from Motion builder. I've just got a relation constraint using the bone rotation to drive the bulge shape channel.

The Absolute modifier just converts the negative rotation into a positive value for the morph. I'd put a clamp on the number so its always 0-100 but I can't remember how to do it right now (it's still early :-)

Hope this helps..


07 July 2003, 09:44 AM
Can you share this fbx?
How'd you get MB aware of the morph?
For the face you must drop a "character" on the face - what did you do for the morph?

btw, here's a link ( that shows how to clamp values.

07 July 2003, 10:01 AM
I imported the mesh from LW with the morph enabled via the Morph Mixer (as you would for a head). The morph data becomes part of the mesh information, when you alt drag the mesh into the relations editor the shape channel should become visible. If not you can add a 'character face' modifier so you can add user channels to control the morph.

oh and I haven't tried this from Maya yet but I'm pretty sure it should all work...

Anyway.. here's the .fbx file for you to dissect.

*** I've updated the constraint from the pic above to clamp the value between 0-100 and fixed it so it doesn't morph when you bend the joint the wrong way ***

Cheers for the clamp link.. I must remember the kaydara forum.


07 July 2003, 06:22 PM
Hey, thanks! :thumbsup:

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