Erens R G, Kappers A M, Koenderink J J
Utrecht Biophysics Research Institute, The Netherlands.
Percept Psychophys. 1993 Aug;54(2):145-56. doi: 10.3758/bf03211750.
Theoretically, metric solid shape is not determined uniquely by shading. Consequently, human vision has difficulty in categorizing shape when shading is the only cue. In the present research, subjects were required to categorize shaded quadric surfaces. We found that they were rather poor at this task; they confused hyperbolic and elliptic (both convex and concave) shapes easily. When a cast shadow visually indicated the direction of the illuminant, they were able to notice the concavity or convexity of elliptic shapes. However, they still confused elliptic and hyperbolic ones. Finally, when an animated sequence of eight intensity patterns belonging to one quadric shape had been displayed, the subjects were able to categorize the quadrics. However, the results are still quite moderate. Our experiments indicate that local shading structure is only a weak shape cue when presented in the absence of other visual cues.
从理论上讲，度量立体形状并非仅由阴影唯一确定。因此，当阴影是唯一线索时，人类视觉在对形状进行分类时会遇到困难。在本研究中，要求受试者对有阴影的二次曲面进行分类。我们发现他们在这项任务上表现相当差；他们很容易混淆双曲线和椭圆（包括凸面和凹面）形状。当投射阴影在视觉上表明光源方向时，他们能够注意到椭圆形状的凹凸性。然而，他们仍然会混淆椭圆和双曲线形状。最后，当展示属于一个二次曲面形状的八个强度模式的动画序列时，受试者能够对二次曲面进行分类。然而，结果仍然相当一般。我们的实验表明，在没有其他视觉线索的情况下呈现时，局部阴影结构只是一个微弱的形状线索。
