I've used the biped guide to make a rig for a model, and when choosing 'skeleton spine' (rather than quaternion), i get an unusable spine. If i try to rotate any of the middle spine bones , the model immediately twists 180 - 360 degrees or more at that bone, and sometimes at an additional spine bone as well, and won't even undo.
I've attached a pic to show what i mean.
Any idea what's happening here? How to prevent this?
I have XSI 6.5 essentials.