Arm IK and hand rig question

#1

Hello!

I’m working on a rig and it’s pretty much finished, but I have a question that I can’t really figure out… Should the hand joint be directly connected to the IK or should there be a joint in between, because right now, when the hands are in direct connection to the elbow and IK it orients automatically when I move the IK handle…

Like this (if the GIF doesn’t loop in your browser the IK is moving from a almost T position to a bent down position, the hand follows the rotation of the arm…)

I hope you understand my question, it’s a quite hard one to express in words! :slight_smile:

#2

Usually what you would do is have the hand as a separate chain. The root of the hand can be the target (goal etc) of the arm Ik chain. It depends on how you set up the arm Ik. I am not sure how you set it up in Maya because I have not done any rigging in Maya. But the basic concept is the same. At the end of the arm IK chain you need something to pull it and position the end of the chain. You can set this up to be the root of the hand chain or a null that also then drives the position of the hand root. Hope this makes sense.

#3

Hi,
I’m not sure if this is helpful and I may I have made some mistakes with this and there probably is an simpler solution.

Suppose have an ik chain with hand joint at where the effector is.
And suppose wanted to control the rotation of the hand joint (the joint at end of the ik chain) and not have it oriented automatically.

Below I’m trying to show how to prevent automatic rotation.
It involves making a duplicate of the existing hand joint. It involves grouping. And it involves point constrain (a way of constraining translation but not rotation).

  1. Duplicate the single hand joint.

  2. Group the duplicated hand joint and put its pivot at the same place as the original hand joint.

  3. Point constrain the group of the duplicated hand joint to the ik chains hand joint (maintain offset on).

  4. Parent the hand geometry to the duplicated hand joint.

What I think should happen when the ik chain is moved is the duplicated hand joint moves too becuase its parent does.
And the duplicated hand joint’s rotations shouldn’t change.

Finally because the duplicated hand joint is free of contrains,connections
(since we grouped it), an animator control can be added to the duplicated hand joint to control its rotations.

Hope this is helpful,

cheers
Nate

#4

Thx to both of you, I’ll fix this the way you said ogbonna, seems like a good solution! It felt like an inconvenience to have the hand directly connected to the IK as it rotates automatically - although, as you sometimes would want this behaviour, I’ll add an controller either parenting its rotation to the IKs or to itself so the animator can choose.

Thanks again, you’ve been very helpful! :smiley:

#5

To keep it simple I usually just have the hand drive the effector. Not the other way around. This gives you one controller for translation and rotation of the hand. If you want other offsets for rotation such as bank for arm roll, you can build those on top of the base hand controller in the chain.

This makes animating simpler and faster if you have less controllers to deal with for most of your initial posing.

#6

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