Best way to do a wrist Twist

#1

Hello CGtalk community,

I hope you all can help me with my rigging issue. I’m working on a low-budget (im not getting payed) horror movie that has a dog/werewolf creature. I’m doing all the 3D myself (modeling, texturing, rigging, animation) and have run into a snag in the rigging process. I’m a decent rigger, but from time to time I either forget or don’t know how to fix things that come up. I’ve tried searching on google, youtube, videos, and books, and maya help to find how to fix this with little luck. Most of the tutorials for wrist Twist setup I’ve seen say to put a joint between the wrist and the elbow and snap the IK handle to the twist joint, then snap the IK’s effector node to the wrist joint. That was how I was taught in school to do it, and it worked fine for cartoon characters - but this creature I’m rigging needs to look more naturalistic and he has some muscle definition on his forearm. When I do the traditional setup I just described, the forearm twists and collapses into itself (see attached). I’ve gone back and tried other setups like other joint locations and an influence object (which I’ve never done before and just followed Maya’s help to setup) both just resulted in the same thing happening.

Any advice from the internet’s Maya experts? Thanks a ton.

#2

Hi …!
Twist bone on the forearm should work. Have 2 or 3 twist bone. Get the Input from the wrist twist Tx and divide it by the no.of twist bone and feed it to the Twist bone.
Rgds,

#3

Thank you for responding shinyprem!

Could you explain further? I’m not quite understanding the part after creating more than one twist joint.

#4

Hi Jeremy,

try the following:

  • create some twist joints (the number depends on how much control you want) by duplicating the elbow joint and placing them equally along the lower arm; the first twist joint is at the elbow though; all twist joints are in a single hierarchy

  • create an empty group “L_arm_twist_grp” and point and orient constrain it to the elbow joint (so that the group has the same placement and orientation as the joints)

  • parent the first twist joint (including the hierarchy) to the L_arm_twist_grp

  • parent the L_arm_twist_grp to the elbow joint

  • create a multiplyDivide node and connect the rotateX (or whatever your twist rotation axis is) of the wrist joint to the input1X of the mult node (use the connection editor or do it via mel)

  • set the operation of the mult node to divide and the input2X to the number of twist joints

  • connect the ouputX of the mult node with the (presumably x rotation) of each twist joint (except the first, as this needs to stay put at the elbow)

(I hope I didn’t forget anything as I’m writing this off the top of my head)

I once made a video tutorial about a pretty good working twist setup but unfortunately (for you) it’s in german, - sorry :wink: But anyway, here’s the link to the first part:

http://www.youtube.com/watch?v=FMl5we_sN08

The lower arm setup is in video 3 (second half) and 4. There is actually an addition in there since the wrist rotation can create some unwanted twist through this setup. I solved this problem by using an additional aim constraint with an up vector object and getting the wrist rotation from there as opposed to the wrist joint rotation itself.

Hope that helps,

Cheers, Ingo

#5

if you wanna try something quick and easy, you could just toggle your skinCluster to dual quaternion

e.g.
http://3.bp.blogspot.com/_qGusuudllf4/TO0an76K7NI/AAAAAAAAAEI/Wz_qM_nu2sw/s1600/dq_twist.jpg

#6

That would have definitely helped a lot, but I’m using maya 2008 at the moment. I have 2011, but haven’t used it much yet. It’s apparently only in 2011.

So since cgtalk didn’t notify me of both of your posts (even though I have mail notification on), I had to spend a bunch of time searching the internet for different options. Ultimately, I found a quick tutorial by a professor Sean Bellinger. It is a simpler, and probably less accurate version of your way Goin. Basically, it had me duplicate the wrist joint (still attached to elbow joint), insert a twist joint between duplicated arm, delete duplicated hierarchy below new twist joint. Then orient constraint (on X only) the twist joint from both the wrist and the elbow. Somehow, having it separate instead of on the elbow-to-wrist fixed my problem. Although, using Goin’s way would have given me a lot more control and naturalism, although with some painting, I think it’s twisting nicely. Thank you both very very much for responding to my thread, hopefully it will help others in need.

#7

You might wanna check this out!

http://suchanspot.blogspot.com/2011/07/twist-joint-setup-overview.html

#8

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