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CHAPTER 5
Interaction with Virtual Crowds for
VRET of Agoraphobia
In this chapter, we describe an application which brings together the work we have described
in the last two chapters, but also some additional features. This application allows
characters to perform gazing motions in a real-time virtual crowd in a CAVE environment.
Moreover, it allows for users to interact with those crowd characters.
First, we adapted the model of visual attention described in the previous chapter in order
to integrate it in a crowd engine and allow it to function online. We also greatly simplified
certain aspects of the automatic interest point detection. Finally, we modified the existing
architecture in order to abide with the limitations induced by the online implementation.
Our final application consists of a city scene, projected in a CAVE setup, and in which
a crowd of characters walks around. We then use a Phasespace optical motion capture device
[Phasespace, 2009] to evaluate where a user is looking and more specifically, which
character he/she is looking at. Finally, we further enhance this setup with an RK-726PCI
pupil/corneal reflection head-mounted tracking device [Iscan, 2009] in order to evaluate
more precisely where a user is looking. Our system then allows the crowd characters to
react to user gaze. For example, since we can determine the user’s position and orientation
in the virtual world, the characters can look at the user.
It is to be noted that the head-tracking alone allows stereographic vision in the CAVE,
using red and blue polarized glasses. In the case of head-tracking coupled with eye-tracking,
however, stereography is impossible as the glasses prevent correct tracking of the pupil and
corneal reflection. More details on the stereographic rendering in the CAVE can be found
in [van der Pol, 2009].
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