View Full Version : Arm Rotation Problem

08 August 2002, 12:26 PM
This should be a common problem to every newbuy animator, but im stuck in it.
The problem is the rotation of the wrist or lower arm.
I have a character in the T positon, with the palm of the hands pointing down. When i rotate the hands so the palm points up the arm gets completly deformed.
Its not a geometry problem, and the bones that i have are:

---sholder ---X -- Upper arm ---X -- Lower Arm X-- Wrist X

It's kinda logic the deformation because we have vertex rotating 180 degrees, but how can i avoid this?

08 August 2002, 03:42 PM
you need to get more of a fall off with your envelope/skinning so that the vertices up the forarm are also twisting. one way to do this is to rotate the forarm itself rather than twisting the wrist, but you will still need a controller for the wrist as well to bend it up and down. just make sure that the forarm and the upper arm envelopes overlap nicely.

hope that helps,

08 August 2002, 12:15 PM

If you rotate the hand 180 degrees, it'll be difficult to avoid the deformation. This is because in the human body, you don't actually rotate the wrist, but the arm and the forearm also. Maya users often slpit arm and forearm bones in 2, in order to have more control on wrists.

So, in your case, to have the palm pointing up, you should rotate the hand, the arm and the forearm. As you can't rotate the elbow in the x axis, some animators add the extra wrist bones I've talked about.

do you know what I mean?

08 August 2002, 12:23 PM
Thank you guys, i've solved things a litle bit diferent, but because my character has a jacket. What i did was creating one extra bone, between the wrist and the elbow, them that bone controled all the and and wrist ( separetd geometry insinde the sleve ) and that bone rotates the hand so i can have the palm pointing up and down, and the wrist then rotates the hand alone.
Kinda hard to explain, and my inglish sucks a bit, but if anyone wants a better explenation i can take some screen shots.

Thanks again guys :)

08 August 2002, 12:37 PM
yes, that's kind of like what I meant.

Go with those screenshots so we can keep helping you :)

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