Biomedical Engineering Reference
In-Depth Information
11.2.2.2 Hand-Held Direction Setting Devices
The most common hand-held devices for setting direction are tracked wands and
joysticks that may or may not be part of a game controller. While the efficacy of
these interfaces is well accepted, they come at the cost of limiting how the user can
use her hands to interact with the virtual scene in application tasks.
Wands and pointing
. Wands typically include a tracker and one or more other
input devices such as buttons. Forward direction can be set by a combination of
arm gesture and a hand-held three degrees of freedom (3DOF) tracker by using the
tracker-measured positions of the user's head and the wand to define the direction
vector. If the tracker is 6DOF, direction of movement can be set from the tracker's
coordinate system; typically movement is in the direction of the longitudinal axis
of the wand. The biomechanics of human shoulders and wrists limit the range of
directions that can be set with wands without repositioning the body.
Joysticks/game controllers
. Joysticks/game controllers can specify motion in any
arbitrary direction, so they are an attractive solution for setting direction. Most often
the user wears a 6DOF tracker on her body and the joystick outputs are interpreted in
that coordinate system. This means that when the user pushes the joystick perpendic-
ularly away from herself, it causes her move in the direction her body is facing. Note
that the tracker data does not restrict the direction of movement; it simply establishes
a body-centric coordinate system for the joystick.
Integrated tracker/joystick and task tool
. The encumbrance of the hand-held in-
terface devices can be mitigated in part if they are integrated into the task tools used in
the IVE system. A well-developed example is the instrumented rifles with integrated
thumb-operated joysticks (thumb-sticks) that are used in many military training sys-
tems, including theUnited StatesArmy's relatively newDismounted Soldier Training
System [
26
]. An evaluation of an earlier system reported both positive and negative
aspects of the thumb-sticks [
25
].
11.2.3 The Future for Walking-in-Place Interfaces
Modeling human walking in ways suitable for use in WIP interfaces is not yet a
solved problem. Techniques inspired by biomechanics have addressed setting virtual
speed during the rhythmic phase of walking and have tried to minimize starting and
stopping latency, but they have not yet addressed the shape of the velocity profile
during those two phases of walking, or variations in speed that may result from
turning or walking with a heavy load. We do not yet know if the discrete changes in
speed that occur in GUD-WIP affect users' perception of the environment or their
task performance. We do not know how the mathematical models may change if the
user is running.
