Environmental Engineering Reference
In-Depth Information
and it realizes it according to the task logics. However, if the object is not reachable, the system
interprets that the user wants to go towards it, it computes the corresponding path and follows
it automatically. To provide more user control on the navigation, the system allows users to
stop and restart the navigation at any time. Observe that the target locationmay not be directly
the object that the user needs to manipulate, but a container in which the object is hidden. For
instance, if the goal of the task is to take out a chicken from the oven, the target direction is the
oven's door in order to open it. Depending on the current level of difficulty of the task user
will have more or less precise instructions on their goal. This is precisely one of the objectives
of the rehabilitation.
The main difficulty with this strategy is that clicking onto the target requires to have it in
the view fustrum and to put the cursor onto it. However, both things require a previous
navigation or camera orientation process. We distinguish two cases: (i) when the target can be
seen without need of modifying the camera position, but only its orientation, and (ii) when the
camera position must be modified. In the former case, we propose two strategies:
free camera
orientation
and
restricted camera orientation
. The
free camera orientation mode
has two degrees of
freedom: yaw and pitch. The camera position is fixed, and users move the viewing direction
until the target is in the center of the view fustrum. The
restricted camera orientation mode
has
one degree of freedom. The system performs an automatic rotation of the yaw angle. Users
only modify the pitch angle. To select the desired orientation, users stop the rotation with a
mouse click.
When the target location is invisible from the current camera position, users indicate
movement by steps, giving a first path direction, stopping the movement to reorient the
camera and clicking again to specify a new direction. In this case, although navigation is
removed, way-finding cannot be eliminated. Therapists must be aware of that in the design
of their tasks. To overcome this problem, inside rooms, we design the scenarios avoiding the
presence of occluders. When the scenario is composed of various rooms, we avoid corridors,
we design doors from one room to the other and put the name of the room on the doors. This
way, to indicate the direction to another room, users click onto the corresponding door.
4.3 Automatic navigation
The automatic navigation method removes the camera control from users. The system
computes the target destination according to the task logics. It puts the camera in front on the
next object with which users must interact. For instance, if users are asked to pick a tomato,
the application places the camera in front of one.
With this mode, the system intervenes in the task development: it takes decisions on the
places to go, and therefore eases the task. It is part of the possible intervention strategies that
therapists can design to help their patients.
4.4 Implementation
In order to manage the described alternatives, the system needs to know the position of all
interactive objects. The position of static objects is part of the scene model. Objects that can
be moved can be on top of or inside other objects. We use a system of grids that allows us to
control the exact position of all the objects at any time of the play. Then, when an object is the
