Types of Size Disparity and the Perception of Surface Slant

Abstract

We examined (i) perceived slant of a textured surface about a vertical axis as a function of disparity magnitude for horizontal-size disparity, vertical-size disparity, and overall-size disparity; and (ii) interactions between patterns with various types and magnitudes of size disparity and superimposed or adjacent zero-disparity stimuli. Horizontal-size disparity produced slant which increased with increasing disparity, was enhanced by superimposed zero-disparity stimuli, and induced contrasting slant in superimposed or adjacent zero-disparity stimuli. Vertical-size disparity produced opposite slant (induced effect) which was reduced to near zero by a superimposed zero-disparity pattern and both patterns appeared as one surface. Adjacent vertical-size-disparity and zero-disparity patterns appeared as separate surfaces with a wide curved boundary. Overall-size disparity produced slant which was enhanced by a superimposed zero-disparity pattern and less so by a zero-disparity line, and induced more slant in a zero-disparity line than in a zero-disparity pattern. The results are discussed in terms of depth underestimation of isolated surfaces, depth enhancement, depth contrast, and the processing of deformation disparity.

Gradients of relative disparity underlie the perceived slant of stereoscopic surfaces

“…For example, there is the wellestablished anisotropy between perceptual responses to horizontal and vertical disparity gradients. Perceived slant around a horizontal axis produced by vertical disparity gradients has a short latency and is close to prediction, whereas perceived slant around a vertical axis produced by horizontal disparity gradients is typically strongly underestimated, with surfaces perceived as much flatter than predicted geometrically (Gillam, Flagg, & Finlay, 1984;Fahle, & Westheimer, 1988;Mitchison & Westheimer, 1990;Gillam & Ryan, 1992;Cagenello & Rogers, 1993;van Ee & Erkelens, 1996;Pierce & Howard, 1997;Wardle, Palmisano, & Gillam, 2014). In addition, slant perception from horizontal disparity gradients is much slower than for vertical gradients (van Ee & Erkelens, 1996), emerging well after stereo fusion (Gillam, Chambers, & Russo, 1988).…”

48.2: Slant Perception as a Function of Size‐Disparity and Image‐Motion

“…Thus, the effect of the disparity magnitude was enhanced by the presence of a ZDS. This depth enhancement effect was previously reported by Pierce and Howard (1997).…”

“…This effect of a disparity image on the perceived slant of a superimposed ZDS is referred to as a depth contrast effect (Pierce & Howard, 1997). However, Figure 4e shows that the mean perceived angle of the pattern-ZDS remained near 0° as the disparity magnitude in the disparity pattern increased.…”

“…Additionally, the interaction between superimposed stimuli and disparity magnitude can be explained by a larger effect of disparity magnitude when a pattern-ZDS was presented. This interaction is referred to as depth enhancement (Pierce & Howard, 1997).…”

“…They conjectured that horizontal-SD may be processed locally, but vertical-SD are integrated globally. This hypothesis was elaborated by Pierce and Howard (1997) who concluded that the perceived slant of an SD surface shown with superimposed ZDS is assessed at each location in terms of the difference between local horizontal-SD and vertical-SD averaged over a large region. Hadani and Vardi (1987) and Vardi and Hadani (1989) reported that under certain conditions motion can interfer with perception of depth in a vertical squarewave random dot stereogram.…”