July 31, 2007
Im looking into areas that can essentially be shared – modular continuity between arms/legs etc on biped and quadrapedal rigs (even bird rigs). Its opened up some interesting ideas namely to first break the lower arm in half and some oddities in the foot.
Breaking the lower arm in half basically allows for a front arm to act like a front leg of a quadrapedal – why is this important well for one thing it allows a quadraped to act like a biped and vice versa. It doesnt mean you would nessesarily use it in a biped rig, but its a simple additional that allows for the control.
For the foot rig – ive seemed to find a stumbling block namely where the control of the foot goes? In human locomotion the pivot exists at the heel, but when its on the ground its at the ball. The problem is even more compounded in that we both swivel and hinge about the heel – hinging is a simple heel<>ball setup, but swivel is more of a problem. Do we change the transform space of the main control if its at the ball or add an additional layered control?
The problem is exactly the same and virtually opposite if the main control is the ankle, you get heel and swivel control but ball of foot swivel is lost. Its not truely lost, you could drive its z rotation of the roll controls z rotation but, as where dealing with ik system our trigonometry plane space would freak out and the foot as a whole would twist – the old gimbal problem looming as two rotations overlap each other.