Workspace calibration via perceptual judgments

3D graphic scenes are only correctly rendered for one viewpoint. Without laborious calibration, however, observers seldom view the monitor from this viewpoint. Even in visual experiments using headrests, inter-subject variability in head-size and eye position result in many subjects viewing the display "off-axis", producing well known distortions in perceptual judgments. The goal is to correctly render graphic displays for the application/experiment based on a simple set of perceptual judgments made by the user. We have two approaches. Our first approach uses point matches between points on a transparency and 3D haptic points that the user makes with the Phantom device. We use well-known calibration techniques from Computer Vision to estimate the transformation matrix between the mirror and the monitor and also the position of the eye. This method requires the presence of a 3D calibrated object (Phantom, in our case). Our second method uses the same transparency and user-adjustable points on the monitor to derive a transformation matrix between mirror and monitor, as well as the position of the eye. This method does not require the presence of a calibrated object and hence is more generally applicable.