My interests range broadly in computer graphics and the affiliated parts of vision, including realistic rendering, material models (optical and mechanical), appearance capture, simulation, and computational photography. Some questions that run through my work are “How can we get objects to appear to be made from exactly the right kind of material?” and “How can we cleverly use cameras to help us measure the information we need to make great images?” Some overlapping areas of activity include the following:
Many techniques for representing the appearance of complex materials, such as spatially-varying BRDFs, BTFs, and BSSRDFs, are fundamentally built around a surface. However, there are many materials—a sweater, a rag rug, a weathered dock, the bark of a tree, even just a patch of dirt—that are not surfaces, and models based on surfaces look wrong when the view gets close. We've worked out ways to compute scattering in hair or detailed geometry volumetrically, and generalized volume rendering to make it work for shiny, oriented materials like cloth.
Since we proposed a now widely used model for light reflection from hair fibers, I have been interested in making hair renderings that more and more closely approach the actual appearance of hair. We've developed several ways to compute multiple scattering, which is important for appearance, as well as a capture method to measure better fine-scale geometry than what's produced by standard hair modeling tools.
Several of our recent projects have addressed cloth: rendering using surface or volume models; simulating it using yarn-based models for better detail.
Diffusion is a very useful model for the flow of light through highly scattering media, such as translucent materials. Recently we generalized this idea to anisotropic materials.
Using cameras in unexpected ways has been part of several projects, ranging from image-based BRDF measurement, to processing range images (3D scans) for the Digital Michelangelo project, to the weird inside-out technique of Dual Photography.
Modeling reflection from surfaces is the classic problem in material appearance. My thesis pioneered the method of image-based BRDF measurement; later we measured and proposed a model for wood surfaces, and measured and proposed a model for transmission through rough dielectric interfaces.