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I'm trying to build a rig for some simple animations and I'm trying to figure out how I can rotate bones around a designated bone as a pivot point. Essentially, what I'd like is to a have a bone (say, a bone at the center of mass or something) whose translation has no effect on the position of other bones, but when rotated, rotates other bones around it as a pivot point.

The pivot constraint seemed like what I'd want, but that causes some strange translations that I can't make sense of, even when the pivot bone isn't moved. Rotating the bones around the 3D cursor and key framing means creating way more keyframes than I'd like or meticulously editing curves to maintain a smooth rotation around the pivot.

Is something like this possible?

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  • $\begingroup$ I'm on mobile for a while, so no pics/real answer, and no rigorous testing to make sure I'm not forgetting to mention anything. But make a bone, duplicate it, parent duplicate to original, give duplicate copy location local->local, XYZ all enabled and all inverted. Move parent, then rotate parent. Moving the parent will not move the child, but child will rotate around the location of its parent with its inherited rotation. $\endgroup$
    – Nathan
    Dec 18, 2022 at 16:38

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You can set the bone child of the rotor base bone and animate its influence slider, using the "Set Inverse" button before enabling the influence:

In my example:

frame 1 rest pose

frame 20 base bone moved, influence slider = 0.0

frame 21 press the Set inverse button, then keyframe influence slider to 1.0

frame 40 rotate the base bone, child follows. Mark with the 3D cursor the loc of the child. Slider influence = 1.0

frame 41 Slider = 0.0, select the child, Shift S > selected to cursor

frame 50 base bone back to rest pose.

You will have to use as many Child of Bone constraints as many different pivot points your animation needs.

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