Game Development Reference
In-Depth Information
manner similar to what has been proposed for continuous control, suggest the user to
position the camera in the position that corresponds to the view he wishes to attain.
Generally, “teleporting'' the user towards his objective is avoided in such a way so as
not to disorient him. So it is preferred to let the machine calculate a path between the
current viewpoint and the one chosen. The viewpoint then automatically follows this
path.
For the exploration type of applications where movements and inspection of
objects in a close-up are researched alternately, Zeleznik et al. (2002) propose an
extension of the solution described above. The use of a virtual ray facilitates the selec-
tion of objects to be observed. Storage of the starting point by the system facilitates a
direct feedback from the user to the initial viewpoint. This technique is called technique
with zoomback or “Zoomback Technique''.
12.4.4 Programmed control
Programmed control is described here briefly because it is not used frequently and does
not reflect one of the major properties of virtual reality that is interaction in real time.
Programmed control consists of describing a path in advance and running it again
during the application. The description of the path in advance is generally realised
on a secondary view that can either be a map or WIM. The path can be described
with the help of one of the solutions seen previously in the section on movement of
the viewpoint or by discrete control. Instead of being carried out immediately, the
movement is recorded and carried out subsequently, upon request.
12.4.5 Evaluations
Whatever be the field of virtual reality, the study of human factors is still of great
importance. The study of movement techniques is no exception to this rule. Some
fundamental research works are carried out on the study of movement in a virtual
environment. These works, however, are still very incomplete and many questions
remain open. As an example, let us cite three fundamental works of assessment of
movement.
Perception of the distance covered: an important characteristic of movement tech-
niques is the ability to provide information on the exact distance covered. There
are numerous parameters that may be involved (and therefore be studied). We
can mention the movement technique used, feedback of the quality and wealth
of visual information, immersion and a possible audio feedback ... Regarding the
study of movement techniques, Iwata (1999), has shown by distance estimation
tests that while using the omnidirectional treadmill that he designed (see the pre-
vious section on treadmills), the underestimation of the possible distance covered
is less compared to the one made while using a joystick.
The comparison of movement techniques: this comparison as well as the cor-
relation with other visual parameters is important for classifying the existing
techniques and for using them carefully. Whitton et al. (2005) propose a com-
parison of three movement techniques: actual walking, walking in place and using
a joystick. The properties of these techniques are studied jointly with several visual
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