Move a root bone without moving its children?

[swingsoneto]

Hi! In setting up a rig, I'm finding that I often need to correct the placement of a parent bone, but I need to keep all its children in place while I do so. Is there a way to do this quickly? I know I can unparent all of its children, move the root, and then reparent everything, but the concern would be that something would get missed and errors would pop up. In the case of some setups, there can be dozens of children parented directly to it.

Is there a native way or a script that can help with this?

I'm also finding that I don't know how to snap the tail of a parent bone back to the head of a child bone. If I unparent the child to move the parent bone, then the connectedness of the two gets broken - I can't seem to find a way to snap them back together. How is this done?

[Greenlaw]

1. Go to frame zero
2. Select all the bones directly parented to the root. Do not select their children.
3. Unparent them. (Parent Tool, click empty space.)

Now, you can move the root bone without disturbing the former child bones. When you're done, select all of the child bones and, with the Parent tool, click on the root bone.

[Greenlaw]

Where these instructions might cause a problem is with Smart Bones parented to the root...Moho could lose track of the base rotation value and it might need to be reset.

To prevent this, I usually parent a separate master bone for Smart Bone Dials. That bone can then be unparented without affecting the rotation of the child bones. Also, if you set this bone to have an Independent Angle constraint, the orientation of your controls will remain fixed, even when the character is flipping in mid-air.

But if you don't have any Smart Bones connected directly to the root, don't worry about it.

Hope this helps.

[Greenlaw]

Another workaround is to parent all the child bones to another bone temporarily. Don't unparent them first, just click directly to the temp parent. Assuming it has the same rotation value as the root bone you're moving, this will prevent problems with parented Smart Bones. The position of the temp bone doesn't matter, only the rotation.

After reparenting the child bones to the root, you can delete the temp bone.

[Greenlaw]

One more tip: Moho doesn't have Bone selection groups, but you can use Stan's Bone Selection Buttons to create a set for the child bones. This could be handy if you foresee doing this more than once with the same rig.

The script can be found here: Bone Selection Buttons