Biomedical Engineering Reference
In-Depth Information
7.4.5 Other Control Inputs
The interaction techniques for travel that we have discussed in the section above
cover a broad range of those that are used in practice. However, the area has seen
a number of innovative techniques. Another way of controlling speed of rotation or
velocity of travel involves measuring the distance between points on the body and
using that as the rate. For example, the distance between the head and a measured
or nominal foot position gives an estimate of lean, and this can be used to control
velocity [ 7 , 16 , 32 ]. Alternatively the distance between hand and head can be used
to control velocity in a point to fly technique [ 22 ].
An alternative to using a device to effect travel is to track a user movement that
is similar to walking. Such techniques are called “walking in place” metaphors,
where users move their feet to simulate walking without actually translating their
bodies [ 31 ]. In the case of Slater et al., the user had to mimic walking, and a gesture
recognition system detected that the user was performing this mime by monitoring his
head movement. Walking in place metaphors have attracted a lot of interest because
users have to physically exert themselves. A novel platform that allowed walking in
place with extended leg movement was presented by Swapp et al. [ 34 ]. Walking in
place techniques are covered in Chaps. 10 & 11 .
Finally, we note that especially with four-walled CAVE™-like systems and HMDs
with restricted tracker spaces, there has been a lot of interest in techniques that bias
rotation to achieve the effect that the user doesn't look away from the main walls, or
walks in the correct direction. These are covered elsewhere in the topic (see Chap. 14 ) ,
but we note the work by Razzaque et al. on redirected walking [ 29 ] which provides
imperceptible rotation distortion, and explicit amplification of rotation [ 16 ].
7.5 Conclusion
We hope that in this short introduction to interaction devices and displays for virtual
walking, we have conveyed some of the challenges of the field and the constant
innovation that there has been over the past couple of decades. Travel is a very hard
problem for virtual reality systems: it is inherently a “two-task” system because the
user can move physically for short maneuvering tasks, but the user also needs a
virtual travel technique to move over long distances. Other chapters in this volume
indicate some of the work that is being done to alleviate the need for a virtual travel
technique in some situations, but virtual travel techniques will likely be with us for
some time yet. In describing the range of different display types, interaction devices
and control methods, it should also be obvious that there are no one-size-fits-all
solutions and that techniques need customization to fit application needs and system
capabilities. While there are many options, there are also established best practices
that can be uncovered by studying the literature. There will no doubt be further
innovation, especially in gesture-based control that is enabled by recent advances in
camera technology. We look forward to testing new techniques as they emerge.
 
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