Spline IK with copy rotation controlled by a ik armature seems unstable

Hello blenders :slight_smile:

I’m trying to create a fk/ik spine rigg but I can’t get the copy rotation to be stable. It “pops” at 90 degrees or something.
I have done something similar with Maya and I would like to do the approximately same setup in Blender.


ikfkspine.blend (488 KB)


The standard IK takes priority which is why you are seeing what your are. Ref: https://www.blender.org/manual/rigging/posing/inverse_kinematics/spline_ik.html

Yes, that is true but it will leave the Y axis untouched. The same link you sent also stated that copy rotation constraint on Y axis should be fine (Roll Control).

It seems that YZX euler does a better job in this case. Now there are no “pop” in the rotation. It would be nice if I could rotate it full 360 degrees but I guess that it would be hard to do that without using dubble controls.

Did you try moving the IK spline above the copy rotation? OK I see what you mean. Is the lower bone in world space an issue? I tried pose and it seems ok. As well as the euler.

I replaced the copy rotation constraints with single property drivers instead. It works better and it also supports more than 360 deg twisting (if that ever will be needed). The controllers needs more work to be user friendly.