Do Any Riggers Know Why The Ulna is Misaligning?

[christopherskokanic]

Hello, here is a quick video, screenshot of the arm's outliner, and scene file of the problem. It is a simple point constraint from the ulna IK to a locater parented under the hand joint. The ulna is parented under the forearm joint. There are also unfinished FK IK joints influencing the main arm joints, but not the actual ulna and radius joints. I am very new to rigging, so I hope this is a simple fix. Anyways, cheers (:

[hamsterHamster]

You probably might wish to parent L_radius_jnt and L_ulna_jnt under L_bicep_FK_jnt, the radius joint should be relocated to more ulna geometry centered position, so that upon twisting, the geo doesn't rotate so drastically within the elbow.

[christopherskokanic]

I couldn't do that because it would cancel out the sliding motion between the humerus and forearm bones. I am ending up just copying a system from another rig I studied, but still am very confused on why my setup was misaligning. Anyways, thank you (:

[christopherskokanic]

I hope I am still able to discover why my setup broke.

[hamsterHamster]

Ok, I assume you want the radius behave like ulna, right? The reason why the radius is rotating is because you are using ikSCsolver and have used ParentConstraint, which affects ikHandle's rotatation. Just break its rotation connections.

[christopherskokanic]

The problem is that when bending the elbow, the ulna pushes away from the locater. Here's a screenshot. It's towards the end of the mp4. Apologies for the miscommunication. 

[hamsterHamster · Accepted solution]

This is why:

.. offsets.. zero'em'out! 🙂

[christopherskokanic]

Dang. Such a simple solution. Thanks! Now I'll never encounter this issue again. I hope this helps others as well. Cheers (: