title: Effects of surface reflectance on local second order shape estimation in dynamic scenes.
abstract: In dynamic scenes, relative motion between the object, the observer, and/or the environment projects as dynamic visual information onto the retina (optic flow) that facilitates 3D shape perception. When the object is diffusely reflective, e.g. a matte painted surface, this optic flow is directly linked to object shape, a property found at the foundations of most traditional shape-from-motion (SfM) schemes. When the object is specular, the corresponding specular flow is related to shape curvature, a regime change that challenges the visual system to determine concurrently both the shape and the distortions of the (sometimes unknown) environment reflected from its surface. While human observers are able to judge the global 3D shape of most specular objects, shape-from-specular-flow (SFSF) is not veridical. In fact, recent studies have also shown systematic biases in the perceived motion of such objects. Here we focus on the perception of local shape from specular flow and compare it to that of matte-textured rotating objects. Observers judged local surface shape by adjusting a rotation and scale invariant shape index probe. Compared to shape judgments of static objects we find that object motion decreases intra-observer variability in local shape estimation. Moreover, object motion introduces systematic changes in perceived shape between matte-textured and specular conditions. Taken together, this study provides a new insight toward the contribution of motion and surface material to local shape perception.
authors: Department of Psychology, Bilkent University, Ankara, Turkey; National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey.
authors: Dicle N
authors: DN
authors: Dövencioğlu
authors: Perceptual Intelligence Lab & Department of Industrial Engineering, Delft University of Technology, Delft, Netherlands.
authors: Maarten W A
authors: MW
authors: Wijntjes
authors: Computer Science Department, Ben Gurion University of the Negev, Beer-Sheva, Israel.
authors: Ohad
authors: O
authors: Ben-Shahar
authors: Department of Psychology, Bilkent University, Ankara, Turkey; National Magnetic Resonance Research Center, Bilkent University, Ankara, Turkey; Department of Psychology, Justus-Liebig-University Giessen, Giessen, Germany.
authors: Katja
authors: K
authors: Doerschner
mesh_terms: D000328:Adult; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D007600:Judgment; D008297:Male; D008962:Models, Theoretical; D009039:Motion Perception / Q000502:physiology*; D057849:Optic Flow / Q000502:physiology; D010775:Photic Stimulation / Q000379:methods; D012044:Regression Analysis; D013499:Surface Properties; D055815:Young Adult
keywords: Shape from motion; Shape from specular flow; Surface materials