ABSTRACT
The arms are in forward kinematic (FK) mode, rotate with the body, and are driven by the shoulder while the arms are crossed and become uncrossed. Arms that are created offset, which causes nicer movement and edge loops, will need extra care to have clean math. If something is broken in the FK arm and the Inverse Kinematic (IK)/FK switch, it isn't going to get any better. Don't waste time building something else on top of it. Cluster is an interesting method where one clusters the lower arm skin, and simply constrains those clusters to rotate with the wrist joint. Using one bone chain with an IK/FK switch. This is a newer method derived after Maya implemented an IK blend attribute for the rotational plane IK handle. The older style triple-chain IK/FK switch method is a hardy solution that works well and is slightly more advanced.
