Rigging and Bone Weighting: Ignore Y Rotation (Twisting), Only Follow X & Z Rotation (Bending)

Question

Is there a way to rig/weight bones such that the mesh doesn't twist along with the bone when rotating it on its Y-axis, and only deforms when the bone rotates on its X and Z axes? In other words, the mesh only follows the bend of the joint, not the twisting?

I need this for rigging loose clothing over my character model. In the real world, one can often twist their upper arm without their upper shirt/coat sleeve following that twist. However you twist your upper arm, the clothing follows the changing direction of the bend of your elbow/forearm, without twisting (like a tuxedo sleeve). The same behavior can be applied to the lower sleeve not following the twist of your wrist or hand.

Is there a way to replicate or closely approximate this behavior in the rigging or weighting process? I need to rig a character with a larger spacesuit design, such as in this Boeing photo.

Answer 1

The simplest way do this is to add another bone that is a copy of the bone with twist (e.g create a forearm-notwist bone from the forearm bone). Make sure it is the same size with the same parent, location and orientation as the bone it copies.

Then add a damped track constrain to your no-twist bone, pointing to your original (e.g. forearm) bone, and change the head/tail slider to 1 (point at the tail.

If you need to you can also add copy location and copy scale constraint to the new bone, depending on what other transforms may be applied to the original.