Wijntjes Maarten W A, Doerschner Katja, Kucukoglu Gizem, Pont Sylvia C
Faculty of Industrial Design Engineering, Delft University of Technology, Delft, Netherlands.
J Vis. 2012 Jan 1;12(1):2. doi: 10.1167/12.1.2.
Among other cues, the visual system uses shading to infer the 3D shape of objects. The shading pattern depends on the illumination and reflectance properties (BRDF). In this study, we compared 3D shape perception between identical shapes with different BRDFs. The stimuli were photographed 3D printed random smooth shapes that were either painted matte gray or had a gray velvet layer. We used the gauge figure task (J. J. Koenderink, A. J. van Doorn, & A. M. L. Kappers, 1992) to quantify 3D shape perception. We found that the shape of velvet objects was systematically perceived to be flatter than the matte objects. Furthermore, observers' judgments were more similar for matte shapes than for velvet shapes. Lastly, we compared subjective with veridical reliefs and found large systematic differences: Both matte and velvet shapes were perceived more flat than the actual shape. The isophote pattern of a flattened Lambertian shape resembles the isophote pattern of an unflattened velvet shape. We argue that the visual system uses a similar shape-from-shading computation for matte and velvet objects that partly discounts material properties.
在其他线索中，视觉系统利用阴影来推断物体的三维形状。阴影模式取决于光照和反射特性（双向反射分布函数）。在本研究中，我们比较了具有不同双向反射分布函数的相同形状之间的三维形状感知。刺激物是拍摄的3D打印随机光滑形状，要么涂有哑光灰色，要么有灰色天鹅绒层。我们使用量规图形任务（J. J. 科恩德林克、A. J. 范多恩和A. M. L. 卡珀斯，1992年）来量化三维形状感知。我们发现，天鹅绒物体的形状被系统地感知为比哑光物体更扁平。此外，观察者对哑光形状的判断比对天鹅绒形状的判断更相似。最后，我们比较了主观浮雕和真实浮雕，发现了很大的系统差异：哑光和天鹅绒形状都被感知为比实际形状更扁平。扁平朗伯形状的等照度图案类似于未扁平天鹅绒形状的等照度图案。我们认为，视觉系统对哑光和天鹅绒物体使用了类似的由阴影生成形状的计算方法，该方法部分忽略了材料特性。
