1. A computer-implemented method comprising: accessing a vehicle occupant packaging design and a task to be accomplished by a virtual human subject within the design, the virtual human subject comprising a plurality of degrees of freedom, the task comprising an endpoint direction of motion; accessing a set of constraints limiting how the degrees of freedom of the virtual human subject are manipulated to accomplish the task; determining a Jacobian between the degrees of freedom and the task during accomplishment of the task, determining the Jacobian comprising determining a manipulation over time of the degrees of freedom of the virtual human subject that accomplishes the task while obeying the set of constraints; and determining a manipulability metric based on the Jacobian and the endpoint direction of motion, the manipulability metric quantifying a capability of the virtual human subject to manipulate the task along the endpoint direction of motion.