Game Development Reference
Figure 12.28 The “Command and Control Cube'' or C 3 . (Illustration: i3D-INRIA, with permission)
We would like to state that the taxonomy of movements proposed for 2D menus also
applies to approaches which are more specifically 3D.
The virtual tool is a metaphor that makes application control very intuitive. The
tool is a concept present in many professions. For example, the carpenter has a number
of tools (wood chisel, plane, saw, hammer, ... ) each meant for a specific use. Selection
of the task to be accomplished (sawing, driving in a nail, planing,...) is done by selecting
the corresponding tool. In a similar manner, the virtual interface proposes a certain
number of tools (in the form of virtual tools), each with a specific function. Selection
of either of these tools ensures the command option. We will note here again that the
boundary between the 3D graphic menu and the selection of virtual tools is a little
vague, and the two approaches can be joined in some cases. On the other hand, the
notion of a tool is important, and selection of physical tools or “props'' (see selection
of physical tools) is an interesting alternative.
In the gestural mode, a command is associated with each hand gesture or posture.
There are mainly two technologies for analysing gestures or postures: vision with
the help of cameras and the use of data gloves. The advantage of this method is in
its relative independence with respect to the visualisation system (it neither requires
display of menus nor the use of selection hardware interfaces that are cumbersome).
On the other hand, it is not very natural and the user may have difficulties in saving
many commands. Wearing gloves can also cause a problem in hand movements and,
above all, “attach'' the user to the movement monitoring system as a result of cables
necessary for connecting the system. The acquisition of gestures by vision resolves
these problems but requires light conditions that are not always compatible with the
visualisation systems. For more details on gestural interaction, see Bordegoni and
Hemmje (1993), Mapes and Moshell (1995), and LaViola and Zeleznik (1999). Note
that the oral and gestural modes do not require a menu to be displayed; display of a
“cue card'' recalling the commands and their oral or gestural equivalents can be very
useful for compensating the problems of memorisation. We will also note, as mentioned