In virtual walkthroughs, the number of Degrees Of Freedom
(hereafter ‘‘DOF’’) of movement varies between 2 and 4, out of apotential 6. Three of the six DOFs involve translation: forward/
back, left/right, and up/down (which is typically not needed in virtual
walkthroughs). The other three DOFs involve rotation: rotation
around the axis perpendicular to the travel plane (yaw axis), and
rotation around each of the axes forming the travel plane (pitch
and roll axes), though the last one is not typically needed in virtual
walkthroughs. Each DOF can potentially be controlled by a different
input device and a different input command from that device.
Moreover, several travel techniques are possible by using one or
two-hands.