I have a Dog Model that I rigged from scratch. I used spline IK constraints for the Eyelids and Lips.

Whenever I move any Ctrl Bones that are hooked to the related bezier curve, the movement of the other closest ctrl Bones hooked to the same curve is almost unpredictable, they twist randomly and sometimes they move so fast that the Mesh deforms radically in that related area. So I have to click Esc to cancel the movement. But even doing that doesn't cancel the movement visually properly, to do cancel it properly I have to hit "rest position" and then hit "pose position". only in that way I can undo the mesh deform. I don't know what I am doing wrong.

I even can not move my Ctrl Root bone, otherwise the same unwanted deformation of spline Ik Constraints do occur again.

I tried with parenting/deparenting The curves to the Armature, didn't help. I also unchecked the Use Curve Radius under chain scale in spline IK constraint tab and used the "volume preservation" for XZ scale mode. It doesn't have any effect on this kind of crazy movements of the bones.

Link video

  • $\begingroup$ Hello and welcome. While files, images, and external videos or links may be helpful additions they should not be the only way to obtain information about your issue. Don't make understanding your question rely on downloading a file, watching a video or visiting an external site. Use the builtin tools to upload images or gifs, along with thoroughly explaining the problem in written form so it can be indexed and searched for thus helping future visitors with similar issues. $\endgroup$ Sep 11 at 14:47
  • $\begingroup$ I think that Crantisz is probably right, that you have dependency loops, but I think you also have other problems as well. Would need a file to be able to tell you definitively what all of the problems were. $\endgroup$
    – Nathan
    Sep 11 at 16:58
  • $\begingroup$ Thank you Nathan for the comment! I hope this link opens for you. Let me please know, if it doesn't ") <img src="https://blend-exchange.com/embedImage.png?bid=eSjKKN2s" /> $\endgroup$ Sep 11 at 19:41
  • $\begingroup$ I can offer that, in addition to the problems Crantsiz detailed, that you have an awful lot of unweighted vertices. (Not sure how you weighted this mesh-- there are a lot of 0 weight groups.) May be other problems as well. $\endgroup$
    – Nathan
    Sep 11 at 22:00
  • $\begingroup$ Thanks a lot! I know, I'm new to the 3D world and my Model and Rig are my second try. eccept The mentioned parts(Lips and Eyelids) I have done the weight painting on the rest of Body ( because of the issue I thought i could do it later) The thing is the curves should follow properly along the movement of the root bone, which don't. If you have trouble to understand how I rigged the lips and eyelids, I used the following Tutorial : youtube.com/watch?v=UdGtmpvOVV4 $\endgroup$ Sep 11 at 23:54

1 Answer 1


This should be caused by loop in parents. It occurs then a bone A depends on a bone B and in the same time the bone B depends on the bone A through several outer bones or constrants.

Click on Window -> toggle system console, it should print out information about loops.

You have a lot of them:

enter image description here

  • $\begingroup$ Thank you for the comment, I reduced some hook modifiers to the curve, the movement caused by ctrl Bones got better and smoother, But the Movement by CTRL Root Bone which moves the whole armature still causes weird deformation. and I'm unfortunately not familiar with The toggle system console, it looks complex due to my low knowledge of programing. I have to search more about it. $\endgroup$ Sep 11 at 19:13
  • $\begingroup$ Thank you Crantisz for the advise! I solved the loops, but the spline IKs on Eyelids and the lips have the same weird behavior as before, whenever I move the whole Armature with the CTRL root bone. I don't understand why the curves don't follow fully, the new file is added to the last comment. I hope you or somebody else could come up with the solution :/ $\endgroup$ Sep 12 at 6:17

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .