The MHX rig can generate IK controls for the fingers and the tongue, but those controls were very difficult to work with and next to useless. Moreover, they caused dependency loops if the character has morphs that affect the fingers and tongue. Recently Alessandro suggested a better way to implement IK for the tongue, using stretch-to constraints, and then I implemented the same mechanism for the fingers. This is not strictly speaking IK since no IK constraints are involved, but it allows the user to place the joints precisely, and we will still refer to it as finger IK and tongue IK.
As with IK for the arms and legs, finger IK is primarily useful when the character interacts with some other object, and we need to place the finger joints precisely relative to that object. E.g., assume that we want to grab a ball. We could proceed as follows:
- Place the IK hand in position.
- Pose the long finger bones so they grab the ball.
- Snap the IK finger joints to the location of the finger bones.
- Tweak the joints so the fingers grab the ball perfectly.
- Optionally snap the FK finger bones, e.g. if we want to export a pose preset back to DAZ Studio.