Virtual Reality: Concepts and Technologies

Visual interfaces 221

to take into account the gaps between the actual position of the eyes and the position

of the tracker fixed on the pair of eyeglasses.

Though this gap varies from user to user (the pair of eyeglasses is worn differently

by each user), it is often possible to consider an “average’’ gap, by considering that the

point tracked is located exactly between the two eyes and the average inter-ocular dis-

tance is 6.5 cm. Alternatively, the two optical centres of the eyes can be determined by

individual calibration by asking each user to point with each eye the targets displayed

on the screen through a tracked tube. The intersection of