This course is about recent advances in the challenging field of physically-based appearance modeling of cloth. Apart from geometrical complexity, optical complexity presents complications as highly anisotropic single and multiple scattering effects often dominate the appearance. Many types of fibers are highly translucent and multiple scattering significantly influences the observed color. Since a cloth model may potentially consist of billions of fibers, finding a viable level of geometrical abstraction is difficult.
After explaining the general structure of several types of textiles, we give an overview of different approaches that have been proposed to render cloth. As the micro-geometry of cloth can be represented using an explicit representation of a fiber assembly, we continue by explaining optical properties of fibers; these can be derived from first principles of physics such as absorption or index of refraction. Understanding light scattering from fibers is essential, when a physically-based cloth renderer is designed. However, as storing these fibers explicitly is often too costly, more efficient statistical descriptions of cloth have also been proposed that can be used together with volumetric rendering techniques to allow for physically-based image synthesis, while retaining most of the flexibility of explicit methods. A major part of this course will focus on these approaches. We discuss the theory and practice of physically-based rendering of anisotropic media. The discussion begins with a review of linear transport theory, upon which current methods for rendering volumetric cloth are based. Relevant implementation details are discussed at each stage, and the final result will be the pseudocode of a Monte Carlo path tracer for volumetric cloth representations. Although rendering of cloth is a very specialized task, many of the concepts, developed in this field, can be used for rendering other materials with complex micro-geometry as well.
For practitioners that are interested in appearance modeling of cloth / physically accurate cloth rendering / volumetric rendering, especially in the context of statistical, volumetric approximations of massive amounts of complex micro-geometry.
The audience is expected to have basic knowledge of rendering methods and material representations.
Kai Schröder, University of Bonn
Shuang Zhao, Department of Computer Science, Cornell University
Arno Zinke, TeamUp Technologies
Kai Schröder has received a german diploma in computer science at the University of Bonn. He was a co-founder of the company Visual Imagination Software / VIS-Games for which he has implemented 3D-engine technology that has been used for several PC and Wii games as well as for industrial prototyping. In 2009 he has received a research scholarship from the Bonn Aachen International Center for Information Technology (B-IT). Since then he is a PhD candidate, supervised by Prof. Reinhard Klein, at the University of Bonn.
Arno Zinke has a computer science and physics background. He received a PhD for the dissertation on physically-based rendering of fiber assemblies from University of Bonn in 2008. Besides his occupation as Chief Scientist of TeamUp Technologies, a company who is bringing 3D creation tools to the cloud, he is also a researcher at the University of Bonn and was lecturing at the University of Frankfurt and the Bonn-Aachen International Center for Information Technology (BIT). His current research focuses on all steps oft he 3D creation pipeline, including appearance modeling, rendering algorithms and computer animation.
Shuang Zhao is a Ph.D. candidate in the Computer Science Department of Cornell University. Supervised by Prof. Kavita Bala, he mainly works on physically-based rendering and appearance modeling. Shuang obtained his Bachelor of Engineering degree from the Computer Science & Engineering Department of Shanghai Jiao Tong University in 2008.