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Abstract:
Depth information from focus cuesaccommodation and the gradient of retinal bluris typically incorrect in threedimensional
(3-D) displays because the light comes from a planar display surface. If the visual system incorporates
information from focus cues into its calculation of 3-D scene parameters, this could cause distortions in perceived depth
even when the 2-D retinal images are geometrically correct. In Experiment 1 we measured the direct contribution of focus
cues to perceived slant by varying independently the physical slant of the display surface and the slant of a simulated
surface specified by binocular disparity (binocular viewing) or perspective/texture (monocular viewing). In the binocular
condition, slant estimates were unaffected by display slant. In the monocular condition, display slant had a systematic
effect on slant estimates. Estimates were consistent with a weighted average of slant from focus cues and slant from
disparity/texture, where the cue weights are determined by the reliability of each cue. In Experiment 2, we examined
whether focus cues also have an indirect effect on perceived slant via the distance estimate used in disparity scaling. We
varied independently the simulated distance and the focal distance to a disparity-defined 3-D stimulus. Perceived slant
was systematically affected by changes in focal distance. Accordingly, depth constancy (with respect to simulated
distance) was significantly reduced when focal distance was held constant compared to when it varied appropriately with
the simulated distance to the stimulus. The results of both experiments show that focus cues can contribute to estimates
of 3-D scene parameters. Inappropriate focus cues in typical 3-D displays may therefore contribute to distortions in
perceived space.
