Abstract
Standard accounts of accretion/deletion treat it as a reliable, self-sufficient cue to depth ordering: the accreting/deleting surface is interpreted as behind the adjoining surface. However accretion/deletion can also result from self-occlusion of a rotating 3D object. When accretion/deletion occurs on both sides of each contour in a multi-region display, one set of regions (odd or even) tends to be perceived as 3D rotating columns, despite the constant-speed motion (Froyen et al., 2013, JOV). Moreover, making one set of regions more “convex” makes them more likely to be perceived as rotating in front (Tanrikulu et al., 2014, VSS). Our rotating columns displays differ from standard accretion/deletion displays along a number of variables. Here, we systematically manipulated these variables to identify the factors that are most relevant to interpreting an accreting/deleting surface as a nearer surface that owns the common border. We manipulated the shape of the border (straight, curved with unbiased f/g geometry, or biased via “convexity”), the number of regions (two, four or eight), and whether accretion/deletion was present only in one set of regions, or in all regions (with opposite motion in alternating regions). In Exp. 1, the width of each region was kept fixed, and in Exp. 2, the width of the overall display was kept fixed. Observers indicated which set of regions they perceived to be in front. In both experiments, accreting/deleting regions were most likely to be seen in front when geometric figural cues were present, and when textural motion was introduced in all regions. The number of regions had a relatively small effect (although this effect was larger in Exp. 2). The findings indicate that the geometry of the occluding contour is a critical factor in the interpretation of accretion/deletion. Computational models of accretion/deletion must therefore include contour geometry as a key component.
Meeting abstract presented at VSS 2015