Game Development Reference
Figure 12.19 “Sticky Finger'' Technique
Figure 12.20 “Head crusher'' Technique
back and forth (with the help of an additional hardware interface: a mouse or another
device) for bringing the object closer or moving it further along the ray. This method
makes it possible to control the distance to the object but requires addition of an extra
input device for controlling the distance.
One technique extending the user's hand reach was proposed by I. Poupyrev et al.
(1996) This was the “Go-Go'' technique. The technique is similar to that of the virtual
hand, with a feature that makes it possible to extend the reach. This feature is the
transfer of real movements of the user onto the cursor (virtual hand) in a non-linear
manner from a distance D: when the user extends his hand beyond this distance D,
the movement scaling coefficient increases (non-linearly) with the distance. It permits
intuitive and natural manipulation, at 6 degrees of freedom (6DoF), for a wide range
of distances. It remains a problem of accuracy over long distances because a small
movement of the human hand translates into a large movement of the cursor.
The “World in Miniature'' technique (WIM) (Stoakley et al., 1995) allows the
user's reach to be extended and provides the user with a miniature model of the virtual
environment (WIM), The user indirectly manipulates virtual objects by interacting with
their representations in the WIM (Figure 12.21). Direct manipulation of close objects
as well as manipulation of 6 degrees of freedom (6DoF) of objects is still possible,
whatever their distance. Manipulation of small objects might become difficult.
The rotation of virtual objects is often a problematic task for virtual ray-based
techniques, essentially with limited degrees of freedom. It is the same with the vir-
tual hand where rotation remains a limitation due to the morphology of the hand.
Poupyrev et al. (2000) propose using “Non-isomorphic 3D rotations''. This involves