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Chapter 5. Interaction with Virtual Crowds for VRET of Agoraphobia
location to define a point of interest and let the virtual characters seem to be aware of the
user. We have equally used a setup in which we added an eye-tracker to the head-tracker.
The eye-tracker allows us to obtain precise gaze values instead of the approximation obtained
with the cap only. In this setup, we use a head-mounted eye-tracking device on which we
fixed three optical markers. By projecting the user’s gaze on screen and using the available
methods in the crowd simulation engine we have used, we determine which character is being
looked at by the user at all times. The user’s position and what or who he/she is looking at
then allow us to define what we consider as the most interesting points in the scene for the
virtual characters to look at.
5.3 Interest Point Definition
In creating this application, our aim was to provide an immersive environment in which a
user could interact with the virtual characters. We thus hypothesized that the user should
be a point of high interest for all virtual characters. Moreover, we hypothesized that what
or who the user is looking at should also be considered as a point of high interest for the
virtual characters. Indeed, when someone around us looks in a specific direction, we have
a tendency to gaze in the same direction to find out what he/she is looking at. Since the
tracking of the user’s head and gaze allow us to define where he/she is standing in the virtual
environment, we just use this position as the interest point to be looked at by the characters.
Similarly, when the user is looking at a virtual character, since we know its position in
the 3D environment, we can use it (at eye height) as a point of interest. Finally, we also
hypothesized that the characters should not always look at the user but should look at other
characters walking around in the environment. The third type of interest point is thus a
random selection of any other character or object in the scene. We have thus created various
modes to determine the points of interest:
User-centered: all characters are interested solely in the participant, and thus look at
nothing else but the participant. The only interest points are the user’s position.
Interest-centered: all characters, apart from the one being looked at, are interested
solely at what the participant looks at. The character being looked at, looks at the user.
The main interest point is thus located where the user is looking at. The user’s position
is the second interest point, only for the gazed at character.
User or Interest: the characters randomly choose to either look at the participant
(user-centered) or at what the participant is looking at (interest-centered). The interest
point is thus either at the user’s position or at the location of the looked at character.
Random: the characters look at any other character in the scene, including the participant.
The choice of character or user to look at is completely random. The interest
points can thus be at any of the character’s or user’s location.
We have created these different modes in order to test which seems the most natural. The
experiment we have conducted to this effect is described in Chapter 7.
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