1. An apparatus comprising: a processing device coupled to memory, wherein the processing device configured to facilitate: head pose estimation logic to determine head orientation of a head of a person in relation to one or more eyes of the person and further in relation to a world reference frame as determined based on orientation of a capturing device, wherein the head orientation further includes a head pose representing a tilt of the head of the person in an image captured by the capturing device of one or more capturing/sensing devices, wherein the image illustrates the 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 in a vertical plane containing the gravity vector and an eye of the one or more eyes, wherein the head pose is based one or more degrees of freedom, wherein a degree of freedom includes torsional rotation including spontaneous controlling when a gaze point is changed, and compensating for the head tilt where the one or more eyes keep their orientation relating to a gravitational horizon of the earth, wherein the total torsion angle relates to torsional rotation that is controlled through a first motion relating to spontaneous changing of a gaze vector or a second motion relating to movement compensation associated with the head tilt; and gaze vector estimation logic to estimate the gaze vector associated with the eye to facilitate tracking of the eye, wherein tracking includes positions or movements of the eye based on the gaze vector referring to a gaze direction, and the gaze point referring to a point of intersection of the gaze vector and a screen, wherein the gaze vector is further estimated based on an optical axis or a visual axis of the eye, wherein the optical axis relates to a first line that passes through a center of curvature of a cornea of the eye and runs parallel to an axis of symmetry, wherein the visual axis relates to a second line that passes through a nodal point of the eye.