title: How little do we need for 3-D shape perception?
abstract: How little do we need to perceive 3-D shape in monocular natural images? The shape-from-texture and shape-from-shading perspectives would motivate that 3-D perception vanishes once low-level cues are disrupted. Is this the case in human vision? Or can top-down influences salvage the percept? In this study we probe this question by employing a gauge-figure paradigm similar to that used by Koenderink et al (1992, Perception & Psychophysics 52 487-496). Subjects were presented degraded natural images and instructed to make local assessments of slant and tilt at various locations thereby quantifying their internal 3-D percept. Analysis of subjects' responses reveals recognition to be a significant influence thereby allowing subjects to perceive 3-D shape at high levels of degradation. Specifically, we identify the 'medium-blur' condition, images approximately 32 pixels on a side, to be the limit for accurate 3-D shape perception. In addition, we find that degradation affects the perceived slant of point-estimates making images look flatter as degradation increases. A subsequent condition that eliminates texture and shading but preserves contour and recognition reveals how bottom-up and top-down cues can combine for accurate 3-D shape perception.
authors.affiliation: Vision Science Graduate Program, University of California, Berkeley, Berkeley, CA, USA. chetan@berkeley.edu
authors.forename: Chetan
authors.initials: C
authors.lastname: Nandakumar
authors.forename: Antonio
authors.initials: A
authors.lastname: Torralba
authors.forename: Jitendra
authors.initials: J
authors.lastname: Malik
mesh_terms: D003867:Depth Perception; D004192:Discrimination, Psychological; D005556:Form Perception; D006801:Humans; D010470:Perceptual Masking; D010775:Photic Stimulation / Q000379:methods; D011601:Psychophysics; D021641:Recognition, Psychology; D015349:Vision, Monocular