Perceived Rotation Axis for Specular, Textured, Uniform and Silhouette Objects K Doerschner1, R Fleming, O Yilmaz2 |
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1Department of Psychology & UMRAM, Bilkent University, Turkey |
| Previously we showed that observers made larger errors in estimating the rotation axis of shiny objects than for matte, textured objects (Kucukoglu, 2010). However, to analyze observers' estimates with respect to veridicality is limiting in terms of understanding how surface reflectance and texture biases the estimate. Here we systematically investigate how observers' perception of rotation axis elevation and azimuth depends on surface material. Stimuli were isotropic objects of four different material categories that rotated in depth through 40 degrees. Rotation axes were systematically sampled from the unit hemisphere, with elevations 10, 20, 30, 50, and 70 degrees and azimuths 0-330 degrees in 30 degree increments. Observers (N=7) repeated every material-rotation axis direction combination once. Modeling the data using the Kent distribution we computed the centroid and spread for observers' estimates for each sampled rotation axis direction. For rotation directions near the line of sight observers' settings across material conditions deviated little form each other in centroid location and spread. For elevations larger than 30 degrees observers underestimated the elevation across all material conditions, however, azimuth of the centroid, mode and spread differed substantially between surface material conditions. We account for these differences with a structure from motion approach. |
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