THE PERCEPTION OF SPATIAL STRUCTURE WITH OBLIQUE VIEWING - AN EXPLANATION FOR BYZANTINE PERSPECTIVE

Earlier work has confirmed that (i) observers can judge divergent rece ding lines, placed directly in front of them, to be parallel, and (ii) converging lines which are displaced laterally, so that they are view ed obliquely, can also be judged to be parallel. The former observatio n is in accord with traditional views of perspective while the latter, which is in accord with the depictions of objects found in Byzantine painting, is not in accord with perspective but is predicted by the re lative magnitude of the visual angles subtended by the near and far en ds of the pair of lines. To investigate whether these effects occurred when the stimulus was clearly three-dimensional, experiments were con ducted with a novel apparatus, consisting of a framework of computer-c ontrolled motor-driven luminous rods. This could be remotely adjusted so that all visible sides appeared to be parallel, ie to resemble a cu be. Results showed that observers set the sides of this trapezohedron framework as diverging when it was viewed immediately in front of them , a result which is concordant with linear perspective, ie they see th e normal projection of a cube as having converging edges. When the fra mework was displaced from the median plane so that it was viewed obliq uely, the sides were set as converging and the magnitude of this effec t was significantly related to angle of view, ie observers see the nor mal projection of a cube as having diverging sides. These results conf irm the suggestion that 'Byzantine perspective' is a legitimate reflec tion of perceptual experience, but they do not provide an explanation why the perception of laterally viewed objects was adopted as a model for centrally depicted patterns.