Visual Perception of Texture

What is visual texture, and how might a study of the visual perception of texture help us to better understand human vision? In this chapter we will attempt to give the reader a feel for how the study of texture perception is useful both in understanding the impact of texture itself, as well as in providing a better understanding of basic visual mechanisms that respond not only to texture but to all visual stimuli. This review will be relatively brief and, of necessity, incomplete. We hope to give an overview of the different research areas concerned with texture perception and of the current issues. For a longer early review, we refer the reader to Bergen (1991). Consider the scene in Fig. 1. The border between the sky and the trees/grass involves a difference in luminance, one that would easily be signaled by a linear mechanism such as a simple cell in primary visual cortex. The boundary between the zebras and the background also involves a change in chromaticity (although not visible in the black-and-white image in Fig. 1), which might be signaled by color-opponent mechanisms. But, the borders between pairs of zebras involve neither a difference in color nor in average luminance. These borders include stretches of boundary that are black on one side and white on the other, stretches where the colors are reversed, and stretches where there is no local visual information to signal the boundary (where black abuts black, or white abuts white). Nevertheless, we perceive a smooth, continuous occlusion boundary at the edge of each animal. It is as if the visual system possesses the capability of segmenting regions of the image based on a local textural property, such as separating " vertical stuff " from " horizontal stuff. " Thus, texture is a property that is statistically defined. A uniformly textured region might be described as " predominantly vertically oriented " , " predominantly small in scale " , " wavy " , " stubbly " , " like wood grain " or " like water. " As Adelson and Bergen (1991) put it, texture is a property of Landy/Graham 3 " stuff " in the image, in contradistinction to visual features such as lines and edges, the " things " in the image (analogous to the linguistic difference between mass nouns like " water " and count nouns like " mouse "). Another way …