Most research in depth-cue combination is based on psychophysical measurements derived from single- and combined-cue computer-simulated (CRT, LCD, etc.) displays. It has been argued that depth-underestimation in single-cue stimuli may arise from flatness cues resulting from pixilation, reduced blur gradient and accommodation due to simulated monitor viewing. When depth-cues are seen in isolation a larger weight may, in fact, be given to the flatness cues and therefore, the single-cue stimuli may appear flatter. To address this issue, we conducted a series of experiments with projectively-equivalent stimuli presented in natural and simulated environments. Stimuli were slanted around the vertical-axis and viewed in three conditions: stereo-only, motion-only, and combined stereo and motion. In the stereo-only condition, the surface was static and viewed binocularly. In the motion-only condition, the surface was viewed monocularly while oscillating around the vertical axis. In the combined-cue condition, the surface was seen binocularly with oscillatory motion. In either a 2-Alternative Forced Choice (2AFC) staircase procedure or an adjustment task, observers compared the depth to the width of the perceived stimuli. Points of Subjective Equality (PSEs) for both natural and simulated viewing conditions were found to be highly consistent with each other: In both viewing conditions, single-cue stimuli were perceived as having less depth than combined-cue stimuli. Moreover, at near viewing distances, combined-cue stimuli were overestimated, whereas single-cue stimuli were underestimated.
Depth from motion and/or disparity in natural and simulated environments: Do cues-to-flatness matter? / R. Shah; F. Domini; C. Caudek. - In: JOURNAL OF VISION. - ISSN 1534-7362. - ELETTRONICO. - 8:(2008), pp. article 851-article 851. [10.1167/8.6.851]