Primary depth cues and background pattern in the portrayal of slant.

A rectangularity postulate has been used in algorithms for the purpose of interpreting two-dimensional representations of rectilinear objects. This rectangularity postulate may affect the perception of true surfaces. In this study, rectangular surfaces and trapezoidal surfaces--the latter simulating the horizontal slant-in-depth of the rectangular surfaces--were viewed under static-monocular, moving-monocular, and static-binocular conditions, both with and without a background pattern. The static-binocular condition elicited the greatest number of accurate responses. The moving-monocular condition did not elicit significantly more accurate responses than the static-monocular viewing condition did. The effect of background pattern was insignificant. These results were unexpected in terms of ecological validity and (regarding moving-monocular viewing) because of the importance of the role of relative visual motion in the detection of object motion. However, the results are consistent with the perception of depth separation of two discrete objects.