Figure 3.

Examples from our image database of material categories: (a) fabric, (b) glass, (c) leather, (d) metal, (e) paper, (f) plastic, (g) stone, (h) water, and (i) wood. We used an intentionally diverse selection of images; each category included a range of illumination conditions, viewpoints, surface geometries, reflectance properties, and backgrounds. This diversity in appearance reduced the chances that simple, low-level information like color could be used to distinguish the categories. In addition, all images in our database were normalized to have the same mean luminance to prevent overall brightness from being a cue to the material category.