The whole thing is based on the position of two objects, one to control the wrist position, the other the elbow.
Instead of an IK blend value to swap between two separate modes, both control objects have an attribute called "lock to control" which does just as it says. The idea is that an animator who perhaps would know almost nothing about CG could still use the setup intuitively.
This setup has various benefits over the standard IK/FK setup:
- Less UI clutter. Uses the same two controls for both IK and FK posing.
- Give the ability to easily pin the elbow to a surface.
- No rotation required so no gimbal lock.
- Easier to make an FK pose than rotating two controls.
The only potential hazard I can see is that the in-betweening will be slightly different when in FK. This is because it is based on the position of objects rather than the rotation. However, once you get used to using positions to dictate an FK arm animation, it becomes really simple and straightforward to use.
http://www.bradnoble.net/rigging/Aiming arm demo.mov (http://www.bradnoble.net/rigging/Aiming%20arm%20demo.mov)
I'm not 100% convinced that this should replace all standard IK/FK setups but everyone I've showed it to really likes the concept.
What do you reckon?