Modeling Human Control of Self-Motion Direction With Optic Flow and Vestibular Motion

In this paper, we investigate the effects of visual and motion stimuli on the manual control of one's direction of self-motion. In a flight simulator, subjects conducted an active target-following disturbance-rejection task, using a compensatory display. Simulating a vehicular control task, the direction of vehicular motion was shown on the outside visual display in two ways: an explicit presentation using a symbol and an implicit presentation, namely, through the focus of radial outflow that emerges from optic flow. In addition, the effects of the relative strength of congruent vestibular motion cues were investigated. The dynamic properties of human visual and vestibular motion perception paths were modeled using a control-theoretical approach. As expected, improved tracking performance was found for the configurations that explicitly showed the direction of self-motion. The human visual time delay increased with approximately 150 ms for the optic flow conditions, relative to explicit presentations. Vestibular motion, providing higher order information on the direction of self-motion, allowed subjects to partially compensate for this visual perception delay, improving performance. Parameter estimates of the operator control model show that, with vestibular motion, the visual feedback becomes stronger, indicating that operators are more confident to act on optic flow information when congruent vestibular motion cues are present.

Perceptual issues in the use of head-mounted visual displays

OBJECTIVE

We provide a review and analysis of much of the published literature on visual perception issues that impact the design and use of head-mounted displays (HMDs).

BACKGROUND

Unlike the previous literature on HMDs, this review draws heavily from the basic vision literature in order to help provide insight for future design solutions for HMDs.

METHOD

Included in this review are articles and books found cited in other works as well as articles and books obtained from an Internet search.

RESULTS

Issues discussed include the effect of brightness and contrast on depth of field, dark focus, dark vergence, and perceptual constancy; the effect of accommodation-vergence synergy on perceptual constancy, eyestrain, and discomfort; the relationship of field of view to the functioning of different visual pathways and the types of visual-motor tasks mediated by them; the relationship of binocular input to visual suppression; and the importance of head movements, head tracking, and display update lag.

CONCLUSION

This paper offers a set of recommendations for the design and use of HMDs.

APPLICATION

Consideration of the basic vision literature will provide insight for future design solutions for HMDs.

Gaze-contingent multiresolutional displays: an integrative review

Gaze-contingent multiresolutional displays (GCMRDs) center high-resolution information on the user's gaze position, matching the user's area of interest (AOI). Image resolution and details outside the AOI are reduced, lowering the requirements for processing resources and transmission bandwidth in demanding display and imaging applications. This review provides a general framework within which GCMRD research can be integrated, evaluated, and guided. GCMRDs (or "moving windows") are analyzed in terms of (a) the nature of their images (i.e., "multiresolution," "variable resolution," "space variant," or "level of detail"), and (b) the movement of the AOI (i.e., "gaze contingent," "foveated," or "eye slaved"). We also synthesize the known human factors research on GCMRDs and point out important questions for future research and development. Actual or potential applications of this research include flight, medical, and driving simulators; virtual reality; remote piloting and teleoperation; infrared and indirect vision; image transmission and retrieval; telemedicine; video teleconferencing; and artificial vision systems.

Effects of a target movement direction cue on head-tracking performance

A review of the literature has shown that most investigations of head-tracking performance have used symmetrically shaped targets. This paper identifies a problem in using circular targets to represent the movement of complex targets (i.e. targets giving directional cues). Two experiments investigated the effects of a target direction cue on head-tracking performance. In the first experiment, practice did not improve performance when tracking either with or without a 'look-ahead trace' showing all target positions 160 ms into the future. A second experiment utilized a 'look-ahead trace' showing target positions with eight different lead-times (0-560 ms). With lead-times of 160 ms or more, significant improvements in tracking performance and subjective difficulty ratings were obtained. Tracking responses were also significantly affected. The results suggest caution when performance data obtained with a symmetrical target are generalized to predict tracking performance with a real target giving cues to the direction of movement. The look-ahead trace offers a systematic means of bridging the gap between a symmetrical target and a real target having direction of movement cues.

Effects of head-slaved and peripheral displays on lane-keeping performance and spatial orientation

To improve the efficiency of images presented in low-cost vehicle simulators, the virtual viewing direction (i.e., the direction in which the image is rendered) can be head-slaved, the display can be surrounded with a less detailed peripheral image, or both. Three simulator experiments were used to evaluate the effect of these techniques on lane-keeping performance and spatial orientation. In Experiment 1, vehicle references or a head-slaved display (HSD) provided feedback on the virtual viewing direction. Vehicle references improved lane-keeping performance somewhat with a standard 50 degrees h x 50 degrees v display. An HSD (50 degrees h x 50 degrees v) allowed better steering performance, but not to the levels obtained with a wide display (150 degrees h x 50 degrees v). Experiments 2a and 2b evaluated the effects of surrounding the HSD with a less detailed peripheral image and of moving the HSD discretely or continuously. With the peripheral image, lane-keeping performance (Experiment 2a) and spatial orientation (Experiment 2b) were similar to those with a wide display. In both experiments, performance with the discretely moving HSD was superior to that with the continuously moving HSD. The results show that low-cost driving simulators can be equipped with more efficient displays that are as effective as wide displays for lane-keeping and spatial orientation.