Depth perception and subjective contours.
A distinction can be made between subjective lines and edges, and subjective lines of the Kennedy-type which suppress (are epistatic to) illusory depth defined by differences of shade.
D003463:Cues; D003867:Depth Perception; D005556:Form Perception; D006801:Humans; D007088:Illusions; D009903:Optical Illusions