Nandakumar C, Torralba A, Malik J, 2011, "How little do we need for 3-D shape perception?" Perception 40(3) 257 – 271
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How little do we need for 3-D shape perception?
Chetan Nandakumar, Antonio Torralba, Jitendra Malik
Received 29 June 2010, in revised form 16 February 2011; published online 18 April 2011
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.
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