In the image shown on the left which side is closer - Orange or Yellow? Why is "which side is closer" an important question?
"Which side is closer?" is an important question because the above image is a part of the natural scene that is shown below. When opaque objects at different environmental distances are optically projected onto a 2D surface so that their projections share an image contour, the laws of optics dictate that the shared image contour belongs to the object that is closer to the point of observation. Because such optical projections lose the spatial dimension of depth, however, the visual system must determine which side of the 2D projection “owns” the shared contour using features of the image regions to determine which side is closer. Identifying and interpreting the visual cues that determine relative depth across image contours (i.e., figure-ground organization) are central problems in vision science.
In the 70+ years since the phenomenon was first discovered by Rubin (1921), very little attention has been paid to the importance of shaded and/or textured surfaces. The goal of the following projects is to identify and empirically study of a novel cues to figure-ground organization in images where gradients of shading, highlights, and/or texture provide information about which side of an edge is closer to the viewer.