Pose won't stay in place when switching to/from rig's edit mode + other problems

I’m new to rigging and as of late I’m toying around with simple models to practice with this subject. In my latest model (a cardboard box, nothing more than a rigging exercise) I’m encountering several problems that I’m not sure if are glitches/bug or the intended result. Perhaps I’m doing something wrong (likely).

This is the .blend file: cardboardbox2.blend (90.1 KB)

  • When selecting the rig and switching to and from the edit mode its pose appears to break apart in random positions with apparently no reason. Is this a bug or the intended behavior? How can I avoid this?

Before selecting the rig and hitting edit mode:


After exiting the rig’s edit mode:


  • When adjusting a bone in pose mode, random parts of the rig appear to wiggle lightly in a random manner. This does not seem to be a weight paint issue. Why does this happen?
  • Are there more efficient, modern or correct ways to rig the cardboard box than I did, anyway? I admit I haven’t followed any tutorial in particular for this.

The cause of #2 is you have several cyclic dependencies going on. With a console window open, tab into & out of edit mode and look at the report in the console window. This is also probably the cause behind #1 as well. I looked at the bones ‘lower north’ & ‘lower north aux’ and you can’t use a copy rotation constraint like that. Basically, you can’t have a parent bone copy the rotation of it’s child bone. You might be able to get away with using a driver, never tried it.

A tip for you: whenever you have bones that flop around or -

When adjusting a bone in pose mode, random parts of the rig appear to wiggle lightly in a random manner.

  • you probably have a cyclic dependency going on.

As to #3, don’t know, never tried to rig a box before…

Randy

Ah, I understand. It’s strange that such critical errors are hidden in the console, I haven’t noticed until you told me.

My idea was to make the small (parent) connecting pieces to rotate with half the angle of their childrens when these ones get posed (so that there’s a “dynamic bevel” — I don’t know how to explain, it’s better if you check in detail how it is made).

I have absolutely no idea on what drivers are at the moment. Maybe I should investigate about it. I was also thinking that probably inverse kinematics could help but again I currently don’t know how to set that up. I have to find tutorials about it, but most of them are about rigging deformable characters rather than undeformable mechanical models.

A tip for you: whenever you have bones that flop around or -

  • you probably have a cyclic dependency going on.
    Nice tip, I’ll keep in mind this next time.

As to #3, don’t know, never tried to rig a box before…
I see, thanks anyway.

I don’t think a driver will help. You will still have a cyclic dependency.

Instead of using copy rotation on the child bone, you could add a third, independent, control bone.
Then you copy the control bones rotation to all relevant bones instead.

Adjust the influences as nessecary, so that the parent bone just rotates half of the amount. And change the rotations to euler instead of quaternions to all bones.