Modeling Hair and Fur with NURBS Anna Sokol ansokol@cs.sunysb.edu Computer Science Department SUNY Stony Brook Abstract: This paper is presenting a framework for modeling hair and fur using NURBS surfaces. This framework will simulate different types of hair from very curvy to straight, from very short to very long, and from very dense to bolding. Each hair strand is modeled using a twisted NURBS cylindrical surface. The hair is modeled on top a plain, a torus, and a sphere. 1 Introduction Realistic hair simulation has been a huge problem due to its incredible complexity. For example, a human head can have over 100,000 individual strands. The simulation of long and/or curly hair creates even more complexity. While movies like Monsters, Inc. and Final Fantasy have been able to generate very realistic looking hair and fur, they weren’t done anywhere near real time. Modeling, styling, simulating, and animating hair remains a slow, tedious, and often a painful process for animators. 1 In this paper, I propose to model hair relatively quickly using twisted NURBS cylindrical surfaces. The hair is rendered in almost real time. It can render 5000 individual hair strands in 5 seconds. The hair can look short or long, curly or straight, and messy or combed. 2 Related Work Hair modeling is a very active area of research and numerous approaches exist. For example, modeling hair using level-of-detail representation 1 where hair is rendered as strands, clusters, or individual strands based on how visible the individual hair strands happen to be. They used butterfly subdivision to represent each cluster or strand and the strips are not necessarily rendered at all. Another approach is to model hair as 2D strips. Each hair strip, modeled by one patch of parametric surfaces in particular NURBS, represents a group of hair strands. A variety of shapes may be defined for each strip. For the rendering, they apply alpha-mapping on the tessellated polygons to achieve a realistic visual effect. 2 Techniques for real-time rendering of fur and hair graphics were presented in [Lengyel 2000; Lengyel et al. 2001; NVIDIA 2001]. However, these techniques do not work well or are not applicable for rendering long, wavy or curly hair. 1 An integrated system for modeling, animating and rendering hair is described in [Dald93]. It uses an interactive module called HairStyler [Thal93] to model the hair segments that represents the hairstyle. 2 To reduce the overall computation time, strands of hair that are near each other or move in a similar fashion, are bundled together as a group or as a wisp [Kurihara et al. 1993]. 1