Exploiting coupled joints - anatomic control of the spine with ik through linearly coupled joints

In this paper we propose a simple model for the coupling behavior of the human spine that is capable of exhibiting anatomically correct motions of the vertebrae in virtual mannequins. Such a model transparently integrates in our inverse kinematics framework as it couples standard swing and revolute joint models. The adjustment of the joints due to the coupling is made with several simple (in)equality constraints, resulting in a reduction of the solution space dimensionality for the inverse kinematics solver. A key benefit is to prevent the inverse kinematics algorithm from providing infeasible postures. We exploit how to apply these simple constraints to the human spine by a strict decoupling of the swing and twist motion of the vertebrae and demonstrate the validity of our approach on various experiments.