I’m trying to set the position of a bone by using one bone to track to (via damped track) and a second bone to establish twist. But I’m getting unexpected behavior when using the copy rotation constraint limited to a single axis. I made a quick demo file:
Demo armature in edit. Only parented bone is PointTarget which is parented to PointTargetParent (in order to move PointTarget while maintaining distance.)
Demo armature in pose mode. PointTargetParent has been rotated arbitrarily and TwistParent has been rotated in its local Y axis (which is the same as the global Z axis.) Constraints for PointAndTwist are shown on the properties view.
So what’s clear from this is that rotation from TwistParent is creating rotation in PointAndTwist that is not in PointAndTwist’s local Y axis. Any explanations? Any recommendations for alternate ways to copy local twist from an arbitrarily positioned bone? (Locked track won’t work because the constrained bone can rotate to any position relative to the TwistParent.)
Blend file is attached.
strangeTwist.blend (87 KB)
Edited to replace the blend, which apparently I’d played with before saving.