Department of Computer Science Colloquium
Thursday February 21st  2002 4:15pm 
Upson Hall B17


Measuring and Modeling the Appearance of Materials for Computer Graphics

 Steve Marschner  
Stanford University - Graphics

Realism has been a fundamental area of study in computer graphics since its inception.  We can approach realism by simulating the physics of how images are formed, an important part of which is the reflection of light by materials in the scene.  Today the quality of models for light reflection is in many cases the limiting factor for realism; current techniques miss subtle but significant aspects of the appearance of real materials.  To build models that capture these subtleties we must first understand the optical phenomena that cause them.  For this reason, advanced light reflection models should be motivated by measurements of real materials. This talk will cover three projects that involve measuring light reflection for the purpose of developing better models for computer graphics.  I will first discuss a novel image-based technique that quickly and accurately measures the angular dependence of light reflection from surfaces.  The technique applies to many materials that cannot be measured by conventional means, and we used it to make the first measurements of this type for human skin.  I will then present a new model for light reflection from translucent materials.  The model is based on diffusion, and it was validated against measurements of several materials.  Finally I will describe an investigation into light scattering by human hair, which revealed new phenomena related to the internal reflection of light within the fibers.  An analysis of light scattering from elliptical cylinders explains these new phenomena and also leads to a practical computational model.

 This is joint work with Steve Westin, Henrik Wann Jensen, Pat Hanrahan, and others.