View Full Version : Arm Twist Controls

06 June 2003, 10:01 AM
I set up a forearm using Jason S's nifty forearm setup but I can't for the life of me figure out how to set up the controls for it. Basically, I have the arm set up with the auto shoulder, and the lower arm with radius and ulna bones parented to the elbow. Can anyone that's used this setup explain how to parent everything and set up the control? Right now, the radius and ulna IK handles are parented to a floating joint to ensure the wrist rotation only effects the radius and ulna for lateral twisting and not up and down rotation. So if I parent this floating bone to the wrist control, it nullifies the effect but if it's not parented to the control, the radius and ulna stay in place.

Just let me know if this needs more explanation.

06 June 2003, 12:15 PM
I don't remember exactly how he had it set up, but i believe he ran out of time... so he couldn't explain it.

I think this tutorial is almost exactly the same, maybe it could help ya out.


06 June 2003, 10:19 PM

If you have the documentation that came with the course/DVD it describes the setup quite clearly. Is there a particular area which isn't making sense?


06 June 2003, 02:24 AM
Hi Jason-
When I orient constrain the wrist joint to the wrist control, the wrist joint flips over. Also when I connect rotate channels, the lateral rotation is reversed. So I think I have something set up flipped. If you have any suggestions that would be most helpful. I'm sure you're hella busy. The point constrain and everything else seems to work fine.
Here's a pic if it helps...

Doogie-Thanks! Yeah, that looks pretty similar. I'm gonna play around with the setup some more.


06 June 2003, 12:16 PM
ah! instead of doing the orientConstraint directly, try duplicating the wrist first, orient constraining to the duplicate, then parent the duplicate under the wrist.. does that work?

cheers! :)

06 June 2003, 09:54 PM
hey muckywetnoodle,

Just to elaborate a little on your problem. Whats happening is that you are orient constraining your wrist to a control that has different orients. And so its trying to take on the same orientation as your control and flipping your joints. The reason Jason is sayin that you must duplicate your wrist is because that way it will have identical orients and no flipping will occur.

The other way around this type of thing for the future is to create a null node and point and orient constrain it to what ever object you want to control it and then parent the object that is to be controlled under the null node. This way you can have 0 0 0 values on the controlled object. (Hope this makes sense)!!

I'm not sure if this helps on the problem you are having with the arm, so forgive me if I'm completely off track!! :sad:


06 June 2003, 01:54 AM
Hey guys,
Thanks a lot! Those both worked. Though an issue I'm having now is that when I rotate the control, since it's orientation is different, rotating one of the axis rotates the wrist and wrist constraint at a slightly skewed angle so I get a mixed 2 axis rotation. Is there a way I can align the control object's axis to the joint's?
Thanks again!

-when in doubt, rig the other side. ;) Found a couple mistakes I made. Still going...

06 June 2003, 10:13 AM
Ack! Finally figured it out. What I did was:
1. Grouped my wrist control
2. selected the new group, set the group transform center to the control center
3. orient constrained the group to the wrist joint
4. deleted the orient constraint from the group node.
5. Orient constrained the wrist joint to the wrist control

So now the wrist control is oriented the same as the wrist joint, zero'd out and the radius/ulna twist only happens for the lateral twist. Lightbulb goes on.

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