Compensation for Viewing Point in the Perception of Pictured Space.
Technical rept. Sep 77-Aug 78,
PITTSBURGH UNIV PA INTERDISCIPLINARY DEPT OF INFORMATION SCIENCE
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Graphic displays can provide a geometrically accurate representation of space if and only if they are viewed from the correct center of projection. Viewing from other locations results in distortions of the virtual space specified by the display. Despite the ubiquity of such distortions they are seldom noticed a fact that has lead some to propose that observers can perceptually discount or compensate for these transformations of virtual space. The present report describes the geometric basis of representationality, and provides a specification of the distortions of virtual space in terms of the geometry of linear perspective. The results of several studies are summarized, and it is suggested that pictorial constancy is based on both an active and a passive compensation process. The active process discounts the distortion by an amount equal to that caused by the discrepancy between the actual viewing point and an assumed correct viewing point. The second aspect of constancy appears to be based on familiarity, and on assumptions regarding the nature of the object depicted. Author