Abstract
In much of the psychological literature, the analysis of 3D shape from texture is described in terms of various attributes of the individual texture elements, such as size, orientation or foreshortening. However, most computational models of this process only make use of the amplitude spectra in local image regions. These analyses typically ignore potential information that is available in the phase spectrum, which is necessary to represent the precise shapes of individual texture elements. The present study was designed to investigate how the phase spectra for different types of texture influence the perceived shapes of ellipsoidal cylinders. The displays all simulated a 20 degree optical projection of ellipsoidal cylinders whose depths and orientations were varied across trials. These surfaces were homogeneously textured with a pattern of randomly placed horizontal and vertical contours, a pattern of random polka dots or a Voronois pattern of randomly shaped polygons. These textures could be presented with their normal phase spectra, or with phase spectra that were randomly scrambled. On each trial observers judged the apparent cross-section in depth of the depicted surface by adjusting the shape and orientation of an elliptical arc presented on a separate monitor. The results revealed that phase scrambling has little or no effect on the perception of 3D shape from contour textures, as has been reported previously (Li & Zaidi, JOSA, 2001). However, when the surfaces were depicted with polka dot or polygon textures, phase scrambling produced significantly higher variance in observers' judgments, and significantly lower magnitudes of perceived depth. These findings suggest that the perceptual analysis of contour and blob textures may involve fundamentally different processes.
This research was supported by a grant from the National Eye Institute (R01-EY12432)