The effects of camera and viewing angles on the perception of 3D shape from texture

Abstract

When observing images of approximately planar surface regions, the scaling and foreshortening of individual texture elements varies systematically as a function of visual direction. There are several different factors that can influence the magnitude of these changes. For example, the range of variation among texture elements increases monotonically with the slant of the depicted surface, and the camera angle that was used to generate the image. Conversely, the magnitude of texture changes as a function of visual direction decreases monotonically for any given image as the observer's viewing angle is increased. The present study was designed to investigate how these different factors influence the perception of 3D shape from texture. Observers were presented with images of convex or concave hyperbolic cylinders with various different types of texture that were rendered with a camera angle of either 20 or 60 degrees. On separate blocks of trials, each image was presented with a viewing angle of either 20 or 60 degrees, and observers were required to indicate its apparent profile in depth by adjusting a curve on a separate monitor that had four possible degrees of freedom. The results revealed that manipulations of camera and viewing angles have opposite effects on perceived 3D shape. For a fixed viewing angle, the judged depth-to-width ratio of a given surface increases with the width of the camera angle used to generate the image. However, for a fixed camera angle, the apparent depth-to-width ratio decreases as viewing angle is increased. These results are both consistent with what would be expected if perceived depth were determined by the gradient of texture scale or foreshortening with respect to visual direction, and they therefore provide strong evidence that texture gradients are an important source of information for the perception of 3D shape.

Footnotes

 This research was supported by a grant from the National Eye Institute (R01-EY12432)