The microscopic appearance of a textile, or cloth structure, has not received much attention until recently. Research in computer graphics related to textiles has focused mainly on the modeling and rendering of the macroscopic structure of woven textiles, e.g., Baraff and Witkin [1], Breen, et al. [2], Terzopoulos and Fleischer [3], Courchesne, et al. [4], and Weil [5]. Knitted textiles have not yet been considered at all because of their very complex physical behavior. The textile industry would clearly benefit from the ability to acknowledge the entire range of textiles, not only their macroscopic mechanical behavior, but also their microscopic visual properties. In this chapter we address possible approaches to both problems. We deal here with knit fabrics in particular since these textiles may be understood as having a more complex and thus more general structure than woven fabrics. Knits are interesting for several reasons. First of all, knits are very important to designers and the textile industry, being used whenever comfort and insulation are required. Unlike woven textiles, which consist of interlaced weft and warp yarns, knits are constructed by the interleaving of loops. The differences between these fabric types are seen in the two samples at the top of Figure 5.1. The more magnified knit sample at the bottom of Figure 5.1 clearly shows the interlocking loops inherent to the structure of knits. Various combinations of these loops can produce an 124almost infinite variety of designs. Knitted fabrics also drape differently from woven textiles, allowing for the creation of endless new looks. These design considerations, along with the wide variety of knitting modules available, make knits vital to the textile industry, and thus deserving of study. Secondly, the problems specific to knitted materials are much more complex than for woven materials, so they are, therefore, a more general model of textiles. Finally, the microstructure of knitted fabrics has rather pronounced 3D patterns. Figure 5.1 Woven and knitted textiles and detail of knit. (See color plates.) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9780429065095/654692cc-6f03-4d35-b228-93a565acace3/content/fig5_1.jpg" xmlns:xlink="http://www.w3.org/1999/xlink"/>