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Erich Graf, Wendy Adams, James Elder; The effect of the bounding contour on the perception of surface shape. Journal of Vision 2015;15(12):732. doi: 10.1167/15.12.732.
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© ARVO (1962-2015); The Authors (2016-present)
The shape of the bounding contour of a smooth object is known to constrain the local shape of the 3D object at its rim: convex points on the contour must project from convex points on the surface, while concave points project from saddle points (Koenderink 1984). While mathematically the bounding contour does not strictly constrain solid shape at points interior to the contour, the fact that silhouettes can convey a compelling sense of 3D shape suggests that the contour may carry useful statistical cues to surface shape some distance from the rim. Here, we use a novel psychophysical method to quantify the effect of the bounding contour on 3D surface shape interior to the bounding contour of an object. Subjects viewed smooth, random ‘potato’ objects, illuminated primarily by a single point light source positioned on one side of the object. We partially occluded the potato shape on the side opposite the lighting direction, and a cutaway in the occluder revealed a silhouetted surface and bounding contour. We manipulated both curvature sign and magnitude of this contour section across trials. The subject’s task was to orient a gauge figure to indicate perceived surface attitude at interior locations over a range of distances from the windowed bounding contour. We found that locations near the boundary were perceived to have larger slant values relative to interior points. Additionally, perceived surface attitude was modulated by both sign and magnitude of contour curvature. We discuss these results in the context of the joint ecological statistics of bounding contour and surface shape.
Meeting abstract presented at VSS 2015
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