Subjects view stereoscopic renderings of 3D objects in a tabletop virtual reality setup and either judge or interact with the virtual objects.
Movements are tracked by using an Optotrak Certus motion-capture system. The motion-capture system is coupled to our tabletop virtual reality environment: subjects look into a half-silvered mirror slanted at 45° relative to the sagittal body midline, and the mirror reflects the image displayed on a 19" CRT monitor placed directly to the left of the mirror.
This arrangement causes rendered 3D objects to appear to be floating in space beyond the mirror. To provide consistent vergence and accommodative information, the monitor is mounted on a linear positioning stage that can be positioned on each trial to match the rendered viewing distance.
Stereoscopic presentation is achieved with a frame interlacing technique in conjunction with liquid-crystal goggles synchronized to the frame rate.
Additional linear positioning stages and stepper motors in the workspace are used to reposition the physical stimuli with respect to the visual stimuli.