Biomedical Engineering Reference
In-Depth Information
Fig. 7.17
Several input devices plotted using the analysis of Mackinlay et al. [
18
]
coordinate system). In covering other sections of the diagram we have included some
other common devices. A trackball senses two degrees of rotation. A dance mat as
might be used for popular dancing games supports approximately 10 buttons that
respond to force applied to them, but do not themselves move. Finally the Spaceball
is a type of controller that sense forces on it, but does not move. One current example
is the HP Spaceball® 5000.
A note: we have not covered treadmills and similar locomotion devices in this
chapter. From a control point of view, these provide one or two degrees of input
because the user can walk in one or two directions. However the issues in using this
for control are subtle. Some treadmill technologies are discussed in Chap.
6
of this
volume.
7.4 Travel Techniques
7.4.1 Travel as a Control Task
In the virtual reality model of interaction, to travel the user would walk or use a
vehicle, just as he would do in real life. Of course, as already discussed, this ideal is
limited by the technology that is available. Most notably, VE systems don't support
the user moving themselves over long distances and might even require that the user
