Information about Three-Dimensional Shape and Direction of Illumination in a Square-Wave Grating

Abstract

A homogeneous grey picture and a 'Mondrian' type of picture were illuminated by a projector with square-wave gratings of thirty different contrast values used as slides. Ten observers reported whether the picture appeared three-dimensional (3-D) (pleated) or flat. 3-D responses in this situation indicate colour constancy 'at the cost of' nonveridical depth perception. The frequencies of 3-D responses were significantly higher for the structured picture than for the homogeneous grey one. In reports of the direction from which the apparent 3-D object appeared to be illuminated there was a significant preference for responses "from above" when the grating was horizontally oriented. With vertical orientation there was no preference for "from the left" or "from the right". The results from the first experiment contradict traditional cue theories of depth perception since the projection of the borders between the fields of the structured picture was invariant and expected to inform about the flatness of the picture. They are, however, in line with a model for perceptual analysis of reflected light into common and relative components proposed earlier by Bergström. The difference in perceived direction of illumination between horizontally and vertically orientated gratings is discussed in connection with human ecology.

Distinctness of perceived three-dimensional form induced by modulated illumination: Effects of certain display and modulation conditions

“…The results confirm earlier observations that the perceived 3-D shape induced by spatial modulation of the illumination of a flat display is much more distinct for structured than for homogeneous displays (Bergstrom et al, 1984). According to traditional theories of depth perception, the geometric projection of the structure of the displays (e.g., the straight and parallel reflectance edges) should inform about their flatness.…”

“…Adelson and Pentland (1990) introduced a marvelous metaphor, the workshop metaphor, for this type of perceptual analysis. Bergstrom et al (1984) predicted, from the model, that a homogeneous gray display would appear less distinctly pleated than a structured Mondrian display would under the same square-wave space-modulated illumination. Their results are clearly in line with the prediction.…”

“…Best known are perhaps those by Hess (1950Hess ( , 1961 and Herschberger (1970). Bergstrom, Gustafsson, and Putaansuu (1984) reported a clear observer preference for perceiving illumination as originating from above by using a Mondrian display illuminated by a square-wave modulated illumination and by comparing the horizontal and vertical orientation of the grating.…”

“…In a series of experiments, Bergstrom (1982) and Bergstrom et al (1984) have studied the effect of display variables on the perceived depth induced by space-modulated illumination. The displays used in those studies were flat, and the illumination was square-wave modulated.…”

The perception of lightness in 3-D curved objects

“…Observers were asked to indicate whether they perceived the test surface (Mondrian or homogeneous surface with superimposed illumination grating) as a 2-D (striped) surface or as a 3-D (pleated) object. Bergstrom et al (1984) found frequencies of3-D responses significantly higher for the Mondrian surface than for the homogeneous gray surface. The results were interpreted as indicating better color constancy in the articulated Mondrian condition since the dark phases of the grating were most likely interpreted as attached shadows.…”