but changing the pivot type doesn’t seem to change the resulting rotation when the X and Y are locked. Atleast not for me! I tried them all, it always rotates around the body laterally
That’s because you locked them at 0.0 . If you have initial rotations to the X and Y axes like in Albinal’s file you will get the same odd behavior Albinal is getting with the pivot set to bounding box …
And no this has nothing to do with quaternions . Quaternions are an “under the hood” mathematical evaluation of bone rotations (under the hood until interaction in the IPO), not a real time interaction issue (and conversely gimble lock can sometimes be a real time interactive issue with Eulers though not so much when dealing with curves directly)
… Just to show you what I mean, place your cursor in some arbitrary point in space then hit the “.” key on the keyboard to set the pivot point to the cursor, you will notice 1) the 3D widget jumps to the cursor and 2) if the bone like in Albinal’s file isn’t an attached bone, it will behave in some very odd ways even with some rotations locked … Though this is actually useful in some situations, setting the pivot to the bounding box isn’t .