Recent Advances in Physically-Based Appearance Modeling of Cloth

Kai Schröder, Shuang Zhao und Arno Zinke
ACM SIGGRAPH Asia 2012: Course Notes, Nov. 2012
 

Abstract

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. For cloth, the finest scale is given by the individual fibers. These have certain optical properties that 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. Explicit representations of micro-geometry are often too costly. Therefore, more efficient statistical descriptions of cloth have 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 context can be used for other materials with complex micro-geometry as well.

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Bibtex

@PROCEEDINGS{schroeder_clothcourse_2012,
     author = {Schr{\"o}der, Kai and Zhao, Shuang and Zinke, Arno},
      title = {Recent Advances in Physically-Based Appearance Modeling of Cloth},
       year = {2012},
      month = nov,
  publisher = {ACM SIGGRAPH Asia 2012: Course Notes},
   abstract = {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. For cloth, the finest scale is given by the individual fibers.
               These have certain optical properties that 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. Explicit representations of micro-geometry are often
               too costly. Therefore, more efficient statistical descriptions of cloth have 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 context can be used for other materials with complex micro-geometry as well.}
}