Environmental Engineering Reference
In-Depth Information
Fig. 3. The six target object strategies to help pointing; A: normal object; B: with rectangular
halo; C: with complementary colors; D: enlarged; E: with increased luminance; F: with
silhouette edges; G: with spherical halo.
selectable objects, we have tested 6 different ways of highlighting them (see Figure 3): (i)
with bounding box halo,(ii) a circular halo, (iii) enlarging size, (iv) changing their color by
their complementary color, (v) drawing silhouette edges and (iv) increasing luminance.
In a first person game with the eye-hand metaphor, dragging objects at their real scale in the
VE can cause collision problems with the other elements of the scenario and occlusions in the
view fustrum. Therefore, instead of moving the geometric model of the object, we actually
move a scaled version of the object projected onto the image plane. We have tested three
different strategies: (i) to substitute the cursor by the object when it is dragged, to keep the
cursor and show the dragged object (ii) centered under the cursor and (iii) separated from
the cursor, at right and below it. We have tested two variants of the three strategies with and
without transparency. Figure 4 illustrates these modes.
A drawback of not moving the actual object is that when users must put it down on a surface,
they don't have a good spatial perception of the free space left. Therefore, we highlight the
free space able to lodge the held object as users move the cursor. We have tested different
ways of highlighting the surface applying different colors and drawing the 3D bounding box
that the object would occupy in the surface or only its projected area (see Figure 5).
3.2 Cognitive assistance
Technological aids can also be used to assist patients at the cognitive level. In particular, to
assist patients in picking a specific object, instead of outlining all the pickable objects, we
can outline only those related to the task goal. In this case, outlining fulfills two different
functions: technological aid and cognitive assistance. The number of visual stimuli is reduced
to only those that are related to the task. As a consequence, the range of strategies to outline
objects is larger: in addition of appearance changes, we can apply sounds and animations that
are not suitable when there is a large number of objects to be outlined.
