Abstract
To construct percepts from binocular information, the visual system must scale the retinal disparities with an estimate of fixation distance. Conventional 3d displays provide conflicting information about fixation distance: frequently, one distance is specified by the disparities, while another is specified by the display's physical distance. Simulated depth cues include the eyes' vergence, and horizontal and vertical disparities. Physical distance cues include focal cues which are retinal blur and accommodation. We have previously examined the influence of mismatches between simulated depth cues and focus cues on 3d percepts (Watt et al., 2005) using conventional displays. In that study, observers could have conceivably used high-level information such as knowledge of the monitor translation. We developed a fixed-viewpoint, volumetric display that allows one to present 3d images at three focal distances simultaneously (Akeley et al., 2004; Banks et al., 2005). Here we examine the utility of that display in minimizing the perceptual consequences of mismatches between simulated depth cues and focus cues. The volumetric display minimizes the contribution of high-level information. The stimulus was an “open-book” hinge textured with random dots. Observers indicated whether the hinge angle was greater or less than 90 deg. In one set of conditions, stimuli were presented on a conventional monitor at one of three physical distances and one of three simulated distances. In another set, the stimuli were presented on the volumetric display (Akeley et al., 2004). From the observers' judgments we determined the “equivalent distance”, the distance estimate that appeared to be used to scale the disparities. Physical and simulated distance cues both affected judgments, indicating that focal cues influence depth percepts. The influence of physical display distance was less in the volumetric display suggesting that high-level cues also affect distance estimates used to scale disparities.