Depth Discrimination from Shading under Diffuse Lighting

Abstract

The human visual system has a remarkable ability to interpret smooth patterns of light on a surface in terms of 3-D surface geometry. Classical studies of shape-from-shading perception have assumed that surface irradiance varies with the angle between the local surface normal and a collimated light source. This model holds, for example, on a sunny day. One common situation in which this model fails to hold, however, is under diffuse lighting such as on a cloudy day. Here we report on the first psychophysical experiments that address shape-from-shading under a uniform diffuse-lighting condition. Our hypothesis was that shape perception can be explained with a perceptual model that “dark means deep”. We tested this hypothesis by comparing performance in a depth-discrimination task to performance in a brightness-discrimination task, using identical stimuli. We found a significant correlation between responses in the two tasks, supporting a dark-means-deep model. However, overall performance in the depth-discrimination task was superior to that predicted by a dark-means-deep model. This implies that humans use a more accurate model than dark-means-deep to perceive shape-from-shading under diffuse lighting.

Evaluating the perception of semi-transparent structures in direct volume rendering techniques

“…Instead it is necessary to take into account the gradient of blurriness, in order to compare the depth of two reference points. In contrast, when using Volumetric Halos and Depth Darkening, the viewer can assume dark-means-deep, as similarly observed also by Langer and Bülthoff [1999].…”

Depicting procedural caustics in single images

“…This approach is based on the idea of "dark-is-deep" which can be seen as one (of possibly several) components of human depth perception [Langer and Bülthoff 2000]. We demonstrate here that it can also be used to produce procedural, perceptually-plausible caustics, relying on two key insights.…”

Inverse Rendering of Faces with a 3D Morphable Model

“…However, faces are not globally convex and it has been shown that occlusions of the illumination environment play an important role in human perception of 3D shape [103]. Prados et al [104] have shown how shading caused by occlusion under perfectly ambient illumination can be used to estimate 3D shape.…”

“…Estimation of 3D shape from ambient shading has received very little attention in comparison to the classical point source shape from shading problem. Langer and Bülthoff [103] showed the importance of ambient shading in human perception of shape. Langer and Zucker [70] were the first to study the problem from a computational perspective.…”