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 dificulty with the biocular display was adversely effected by the visual task. This viewing dtfficulty is likely due to conflict between looming and stereo disparity cues. A second experiment examined the precision with which operators could manually move ringshaped virtual objects over virtual paths without collision. Accuracy of per$ormance was studied as a function of required precision, path complexity, and system response latency. Results show that high precision tracing is most sensitive to increasing latency. Ring placement with less than 1.8 cm precision will require system latency less than 50 msec before asymptotic per$ormance is found.Introduction.
Virtual environment interfaces to computer programs in several diverse application areas are currently being developed. The users of virtual environments will require many different methods to interact with the environments and the objects in them. This paper reports on our use of virtual menus as a method of interacting with virtual environments. Seveial aspects of virtual environments make menu interactions different from interactions with conventional menus. We review the relevant aspects of conventional menus and virtual environments, in order to provide a frame of reference for the design of virtual menus. We discuss the features and interaction methodologies of two different versions of virtual menus which have been developed and used in our lab. We also examine the problems associated with our original version, and the enhancements incorporated into our cuirent version.
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