Experiments were conducted to determine how the ability to detect and discriminate head-motion parallax depth cues is degraded by time delays between head movement and image update. The stimuli consisted of random-dot patterns that were programmed to appear as one cycle of a sinusoi dal grating when the subject's head moved. The results show that time delay between head movement and image update has essentially no effect on the ability to discrimi nate between two such gratings with different depth char acteristics when the delay is less than or equal to roughly 265 ms.

The management of a large number of manuscripts is integral to the publishing of a scientific journal. The process of submitting articles should be as simple as possible, both for the sake of the authors and for the reduction of the overhead associated with mailing and handling. For these reasons, the entire pre-press process at Presence is now based on standard Internet protocols. Although a hardcopy document is still required by the publisher, the pre-press process—from original submission through the stages of review—to final acceptance for publication—can now be done electronically. All functions involving electronic manuscript submission and management, as well as correspondence with reviewers, has been bundled in a modular package amenable to modifications. This publishing system was developed in-house at a fraction of the cost of acquiring a commercially available system. It was designed in close cooperation with the editorial staff to ensure optimal functionality.

A prototype near-field virtual environment system is described that incorporates a CrystalEyes stereoscopic display (viewed in a mirror), a PHANToM manipulandum, and a stereo auditory display. The apparatus, which was designed to achieve registration of three sensory modalities (visual, haptic, and auditory), has a wide range of applications and has been used for both psychophysics and training research. Calibration-verification experiments are described in which human subjects positioned a physical probe attached to the manipulandum so that it appeared to coincide with a visual target on the stereoscopic display. The readings from the manipulandum and the calculated positions of the targets corresponded roughly within ± 0.5 cm over a large volume, although differences greater than 1 cm were observed near the sides of the workspace. The calibration of the manipulandum was tested independently on the z axis (running through the center of the workspace), and the perceived depth of the targets (probe z coordinate) was found to agree with the calculated depth within the accuracy of the measurements (± 0.4 cm). Some subjects had poorer positioning resolution when the visual target was far from the plane of the display screen (although their mean response was unaffected), and we hypothesize that this may have been caused by the different levels of accommodation that were needed to view the physical probe and the displayed target.