Environmental Engineering Reference
In-Depth Information
and minimize its side effects in the rehabilitation process. These strategies, combined with
customized intervention strategies, can contribute to the success of CNVR.
In this paper, we propose and discuss several strategies to ease the navigation and interaction
in VEs. Our aim is to remove technological barriers as well as to facilitate therapeutic
interventions in order to help patients reaching their goals. Specifically, we present
mechanisms to help objects picking and placement and to ease navigation. We present the
results of these strategies on users without cognitive impairments.
2. Related work
Several studies have shown that virtual objects manipulation improves the performance of
visual, attention, memory and executive skills (Boot et al., 2008). This is why typical 3D CNVR
systems aimed at training these functions reproduce daily life scenarios. The patients exercises
consist mainly in performing virtually domestic tasks. The principal activity of patients in
the virtual environments is the manipulation of virtual objects, specifically, picking, dragging
and placing objects (Rose et al., 2005). These actions can be performed through a simple user
interaction, in general a user click having the cursor put onto the target. More complex actions
can be performed, such as breaking, cutting, folding, but in general, all can be implemented as
pre-recorded animations that can also be launched with a simple user click (Tost et al., 2009).
The intervention strategies that help patients in realizing these activities by their own consist
in reminding the goal through oral and written instructions and attracting the patients
attention to the target through some visual mechanisms. Difficulties arisen from the use of
the technology are related to the users ability in recognizing target objects, understanding
the rules and limitations of virtual manipulation in comparison to real manipulation and
managing the scale of the VE. In particular, the selection of small objects in cluttered VE
can be difficult. To overcome this problem, a variety of mechanisms has been proposed
(Balakrishnan, 2004), mainly based in scaling the target as the cursor passes in front of it.
Another interesting question is the convenience of decoupling selection from vision by using
the relative position of the hand to make selections, or by applying the hand-eye metaphor
and computing the selected objects as those intersected by the viewing ray (Argelaguet &
Andújar, 2009).
To be able to reach the objects and manipulate them, patients must navigate in the
environment. However, navigation constitutes another type of activity that involves by itself
a lot of cognitive skills, some of them different that those needed for objects manipulation.
It requires spatial abilities, namely spatial orientation, visualization and relations (Satalich,
1995) and temporal skills to perceive the direction of movement and the relative velocity of
moving objects. Moreover, navigation is closely related to way-finding. It requires not only
a good navigational awareness, but also logic to perform selective searching of the target
in semantically related locations, visual memory to remember the places already explored
and strategy to design efficient search. In fact, although some controversy exists on if virtual
navigation enhances or not real navigation abilities (Richardson et al., 2011), virtual navigation
by itself is being used for the rehabilitation of spatial skills after brain damage (Koenig et al.,
2009).
