Information Availability in 2D and 3D Displays

51 A ir-traffic controllers, military personnel, and others need displays that rapidly convey the location and other attributes of objects (such as aircraft) in 3D space. The ongoing revolution in the availability of inexpensive and fast 3D rendering technologies is allowing display designers to develop 3D prototype displays for this purpose, such as Figure 1. 1 By 3D display, we mean a display that shows a perspective scene view on a flat CRT. The image is 2D, but the oblique viewing angle means that all three dimensions are projected and represented, to provide a 3D perspective. Various other true holographic and stereo-scopic 3D displays are under development (such as Travis et al.'s 2) but most interest in 3D displays is in flat-screen displays like Figure 1. As part of a wider research effort investigating how and when to use 2D and 3D displays for operational tasks 3 and what symbology we should use to populate them, 4,5 we wanted to find out which characteristics of 3D display actually do enhance performance. We have several reasons to believe that 3D displays may be preferable to conventional 2D displays that show an environment from directly above. First, because our retinal images are perspective projections of the world, 3D displays may be more ecologically plausible than 2D displays. Similarly, their naturalistic look has led some 3D display designers to suggest that they may require minimal interpretive effort. 1 Second , because 3D displays integrate all three dimensions of space into a single display, users may be spared the mentally demanding process of scanning back and forth to integrate two planar views to gauge 3D spatial relationships. 6 Third, users simply prefer the familiarity and easy feel of 3D displays. However, counterarguments exist to each of these points. First, if a scene were reproduced with the exact same fidelity as retinal images of that scene, the brain would still need to interpret those images. There's more to applying perceptual principles to display design than simply mimicking the retinal images of a scene as closely as possible. A century of perceptual work since Helmholtz has documented the difficulties inherent in scene interpretation: vision is hard. Second, the compression of three dimensions onto a flat display integrates all dimensions but leaves each one somewhat ambiguous (see Figure 2, next page). This ambiguity, coupled with the distortion of distances and angles inherent in a perspective projection, makes …