Texte intégral / Full text (pdf, 20 MiB) - Infoscience - EPFL

5.2. Tracking in the CAVE
animation. This allows for the characters to maintain their original walking motions as much
as possible. In this Gaze phase, we first determine the interest point for the current character.
We then compute the motion adaptation which would be needed to satisfy this constraint.
Finally, we determine the quantity of this adaptation which has to be done at the current
phase depending on spatial and temporal factors.
Spatial Resolution
Real-time Simulation Loop
Simulation
Animation
Interest Points
Motion Adaptation
Rendering
Gaze
Temporal Resolution
Figure 5.2: Crowd engine real-time simulation loop pipeline.
5.2 Tracking in the CAVE
By definition, the tracking of the user’s head in the CAVE is a necessary step. First of
all, in order to compute the correct projection matrix for the CAVE screens, the position of
the user’s eyes needs to be known. This can be approximated by tracking the user’s head.
In order to do this, we use a regular baseball cap on which we fixed three motion capture
markers. Using the positions of these three markers, we approximate the user’s eyes position.
Second, the tracking of the head also allows us to determine the user’s head orientation. We
can thus determine the user’s gaze direction and by projecting the POR, determine which
character he/she is looking at at all times. Finally, the position of the markers allows us
to determine where, in the 3D environment, the user is located. We can thus use the user
65