1. An apparatus comprising: head pose estimation logic to determine a head pose representing a tilt of a head of a person in an image captured by a capturing device of one or more capturing/sensing device, wherein the image illustrates one or more eyes of the person; gravity vector estimation logic to estimate a gravity vector relating to an eye of the one or more eyes based on data relating to the image and sensed by a sensing device of the one or more capturing/sensing devices; torsion estimation logic to compute a total torsion angle based on one or more of the head pose and the gravity vector; and gaze vector estimation logic to estimate a gaze vector associated with eye to facilitate tracking of the eye, wherein tracking includes positions or movements of the eye based on the gaze vector.