Egan Eric J L, Todd James T
Department of Psychology, the Ohio State University, Columbus, OH, USA.
J Vis. 2015 Feb 24;15(2):24. doi: 10.1167/15.2.24.
Human observers made local orientation judgments of smoothly shaded surfaces illuminated from different directions by large area lights, both with and without visible smooth occlusion contours. Test-retest correlations between the first and second halves of the experiment revealed that observers' judgments were highly reliable, with a residual error of only 2%. Over 88% of the variance between observers' judgments and the simulated objects could be accounted for by an affine correlation, but there was also a systematic nonaffine component that accounted for approximately 10% of the perceptual error. The presence or absence of visible smooth occlusion contours had a negligible effect on performance, but there was a small effect of the illumination direction, such that the response surfaces were sheared slightly toward the light source. These shearing effects were much smaller, however, than the effects produced by changes in illumination on the overall pattern of luminance or luminance gradients. Implications of these results for current models of estimating 3-D shape from shading are considered.
人类观察者对由大面积灯光从不同方向照亮的平滑阴影表面进行局部方向判断，这些表面有或没有可见的平滑遮挡轮廓。实验前半段和后半段之间的重测相关性表明，观察者的判断高度可靠，残余误差仅为2%。观察者判断与模拟物体之间超过88%的方差可以由仿射相关性解释，但也存在一个系统的非仿射成分，约占感知误差的10%。可见平滑遮挡轮廓的存在与否对性能的影响可忽略不计，但光照方向有微小影响，即响应表面会朝着光源方向稍有剪切。然而，这些剪切效应比光照变化对整体亮度模式或亮度梯度产生的效应要小得多。文中考虑了这些结果对当前从阴影估计三维形状模型的启示。
