Relationship between monocular and binocular depth cues for judgements of spatial information and spatial instrument design

The purpose of this study was to investigate the use of monoscopic and stereoscopic depth cues for spatial instrument design. Ten volunteer subjects judged the depth and altitude separation between two computer-generated objects located above a ground plane using either a stereoscopic or perspective display. The depth cues manipulated in the study were shadows, a texture gradient, droplines from the cubes to the ground plane, and the presence or absence of binocular disparity. The results indicated that depth judgements were significantly improved with the addition of both monocular and perspective depth cues while judgements of altitude were not. Furthermore, the addition of droplines to the display had the most significant effect on the accuracy of depth judgements, while the addition of a texture gradient on the horizontal grid plane had the least effect. It was also shown that the addition of shadows improved the accuracy of depth judgements but only slightly more than the addition of texture. When droplines were present, the addition of shadows did not add to depth perception nor did the addition of a texture gradient help depth perception if droplines were not present. Finally, stereoscopic viewing did not provide enhanced performance over perspective displays but did aid subjects in making more consistent spatial judgements regardless of the location of the target cube relative to the reference cube. Implications of the results for the design of spatial displays are discussed.