Random bone scaling during movement

I’m new here, but I’ve found some really helpful stuff on this forum so I thought I’d ask.

I’m working on a character for an animation project, and I’m almost done. But whenever I move my rig to move the character, the eye bones scale randomly. I have done some checking and it seems to be caused by the IK constraint modifier on the bones, because this does not happen when I turn it off. Because this is a new account, I am not able to upload a video of this problem, if needed I can try to figure out a shared link or something to share it.

I have looked around on here and haven’t been able to find someone else that has experienced this specific issue before. Any suggestions would be appreciated!

Hi, you have narrowed down the origin of the problem already. Now why do eye bones have ik constraints ? This seems strange to me. IK bone chains can scale if set to stretch in the constraint properties and have non-zero value in their own bone properties, inverse kinematics panel. Try setting those to zero, see what happens.

Hello, I tried what you had mentioned, but the issue still occurs. Here is what happens:

Here are my IK settings, and a video of why I have the eyes rigged that way as well.

Can I see the file ?
Wait, you’re using the same bone as pole target, I think it may be why it’s flipping out.

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It looks to me like you have somehow nominated the eye bone itself as the pole target of the IK. You can’t do that. Think of the pole target as being the point that the bone’s X axis should point at. That can’t be itself. I can imagine this as a dependency loop, although I’m not sure a single bone dependency loop would even show up in the warnings…

For a single bone IK, I can’t imagine a single situation where I’d be using a pole target. (Pole targets are optional, not sure if you know that.) Although in this situation, I would probably not be using IK at all, but a damped track constraint.

Edit: Don’t know how I stepped on Hadriscus-- maybe looking at a window that had been open for a while. Apologies!

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That fixed my issue! Thank you! I’ll look into the damped track constraint, I’m new to rigging and I didn’t know that the pole target was optional. :sweat_smile:

Removing that fixed it, thanks!

Did you step on me ? I only felt a gentle breeze

Anyway, nice to see it is fixed !

This is a common problem but everything is explained here: