Abstract

When we look at a line drawing of a Necker cube, we see it as a wire frame with empty space between the black lines. With a drawing of a solid cube, however, we see each area bounded by black lines as an opaque surface with a particular orientation and depth. We examined the nature of the depth and surface inferences in line drawings by replacing the lines of the original drawings, strips of black on a white background, by lines defined by other attributes: color, texture, motion, or depth. Drawings represented by any of these attributes were able to signal shape and occlusion showing that the outline representation is analyzed at a high level, following the reintegration of the multiple representations of visual attributes such as color and motion (Zeki, 1978). Surfaces sharing the same color or texture showed no tendency to group across an intervening line; the occlusion and crossing cues provided by the intersections of contours were able to break the surface into different depth planes. Surfaces sharing common motion or depth grouped strongly, however, and often could not be seen at different depths even though separated by intervening motion or depth lines.

© 1985 Optical Society of America