Factors influencing operator interaction with virtual objects viewed via head-mounted see-through displays: viewing conditions and rendering latency

A head mounted visual display was used in a see through format to present computer generated, space stabilized, nearby wire like virtual objects to 14 subjects. The visual requirements of their experimental tasks were similar to those needed for visually guided manual assembly of aircraft wire harnesses. In the first experiment subjects visually traced wire paths with a head referenced cursor, subjectively rated aspects of viewing, and had their vision tested before and after monocular, biocular, or stereo viewing. Only the viewing difficulty with the biocular display was adversely effected by the visual task. This viewing difficulty is likely due to conflict between looming and stereo disparity cues. A second experiment examined the precision with which operators could manually move ring shaped virtual objects over virtual paths without collision. Accuracy of performance was studied as a function of required precision, path complexity, and system response latency. Results show that high precision tracing is most sensitive to increasing latency. Ring placement with less than 1.8 cm precision will require system latency less than 50 msec before asymptotic performance is found