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For example, if we carry out a projection of the perceptual space of a user,
u
,
according to the visual modality and with constant attributes (e.g. with a given
character size), we obtain a
visual field
. A visual field is represented in Figure 10.3:
information displayed on screens A and B are perceived by user
u
, but not those
displayed by C.
Figure 10.3.
Special case of perceptual space: visual field of a user, u
10.4.3.2.
Space of influence
We now have all the necessary notions for the definition of
reciprocal
notion of
perceptual space. Perceptual space characterizes the perceptions of an entity, in
other words its
inputs,
i.e. its behavior as a
multimodal receiver
. However, an entity
can also be a
multimodal emitter
, i.e. present output multimodal characteristics. Just
as input characteristics are portrayed by perceptual space, output characteristics are
portrayed by what we call the
space of influence
.
Formally, we define the
space of influence
of an entity
e
vis-a-vis
an entity
d
as
being all the points
x
of the physical space
E
from which
d
can perceive
e,
i.e. for
which
e
belongs to the perceptual space of
d
when
d
is situated in
x
.
The space of influence is defined
in relation to a receptive entity
: as the
perceptual spaces are different for each entity, the perception of an
emitter
in a
given point in space will or will not be possible depending on the entity considered.
It is therefore impossible to define a space of influence in absolute terms. Figure
10.4 deals with the simple case where the only modality considered is visual text.
