Bone Constraint Problems

Hey guys,
I’ve been working on a particular scene and I have seem to come across a strange problem. When I rotate my IK hand bone by 90 degrees on the Y-Axis, the main hand bone does not rotate properly. The main bone has a copy rotation constraint to the IK hand bone.



Do you know how this can be fixed?

Hi, check those two bone’s roll values (in transform panel) - they need to be the same.

They are exact duplicates and have the same bone roll values. I suspect it’s a problem with the constraint.

The bones are identical and have the same bone roll values.

The bones are identical and share the same bone roll values.

Hmmm, maybe another constraint on top of copyrot could be interfering with the result ?

Have you got the copy rotation constraint set to local space for both space settings?

There isn’t another constraint on top of copy rotation.

No, both the target and owner are in world space. Setting either to local space or both to local space messes up the orientation of the hand.

If it’s any help, the claws are parented to the main hand bone. I don’t believe this is the problem as deleting and replacing the claws, deleting and replacing the hand IK bone, or even deleting and replacing the main hand bone itself does not fix the problem.

PS. Sorry for the multiple posts, my computer randomly shut down and I wasn’t sure if I had replied.

Do you know if I should completely restart or am I overlooking something?

Can you post a blend file with just the armature in it, I will take a look at it.

Cheers, Clock.

Sorry, how should I upload the model?

Where should I upload the model? (I double posted as I am deleting the first post).

Here it is:




Double hand bones on the right hand, I removed one.

IK chains not at all correct, I changed them.

Some bone parenting and connections wrong, I altered them.

Here you are:

Problem Model-1.blend (1.11 MB)

You need to look at some movement constraints.

Sorry for quick reply, Mrs. Clockmender is calling… :yes:

Cheers, Clock

Thanks, Clockmender! The reason I had two bones for the hands are because I made the rig with a hand bone to control the hands, and the hands were rotation constrained to the hand IK bones. I see you deleted the hand bones and parented the hands to the hand IK bones. The only problem is I don’t generally like that setup. Could you make it work without deleting the main hand bone? I know it is possible as I use that technique with all of my rigs and they work fine. If you would like to know where I learned it, check out BornCG’s tutorial on IK rigging Pt.1/3.

Does anyone know why specifically it doesn’t work? In theory it should work fine. Is it a problem with Blender?

Ideally you should position the control bone so it is not coincidental with a deform or IK target bone, I will add one later today when I have some free time. Can I presume you want both hands to rotate the same way? Maybe in opposite directions so they clamp together when you rotate the control. This method lets you move the hands independently or together. Coincident bones, just causes confusion in trying to locate the right one, and also is not good practice if someone else does the animation after you do the rigging. It does not look like a Blender problem to me, just a case of tuning the rig.

Cheers, Clock.

Take a look at BornCG’s tutorial on IK rigging Pt.1/3 around the 22 minute mark. That’s what I am trying to achieve. His method for IK rigging hands has always worked for me until this project so I was confused why it didn’t work this time. Also the reason that the IK bone was in the same position as the original hand bone was so that the mesh was parented to the original hand bone and that original is constrained to the IK bone. The original would be on a separate bone layer so you wouldn’t get confused.

Give us the link so we don’t have to search for it.