Appearance Based Rendering

April 21, 2001 -
10:00am to 11:00am
6-212 EE/CS Building
The characterization of appearance by the paint and coatings industries has resulted in a set of appearance measurement standards. Tristimulus colorimetry, which is essentially a measure of diffuse reflection color, is one example with which computer graphics professionals are already very familiar. However gloss, a measure of the magnitude of the specular reflection, and haze, which captures the width of the specular lobe, are both almost unknown terms within the computer graphics community. Gloss and haze demonstrate the critical importance, for appearance measurement, of knowing how much light is reflected within just a few degrees of the specular direction. Even when the magnitude and color of the reflected light change over the entire reflectance hemisphere, appearance professionals have learned that in many cases, such as automotive metallic and pearlescent paint, only a few key measurements are necessary. Finally, the measurementonly a few key measurements are necessary. Finally, the measurement of gloss, haze, metallic paint and other standardized appearance parameters can all be accomplished with relatively inexpensive measurement instruments.

This talk applies current appearance standards and simple appearance measurements to realistic image synthesis. Given existing computer graphic reflection models such as the Phong model, the Ward model and the Cook-Torrance model, a correspondence is developed between the parameters of these models and appearance measurement scales such as gloss and haze. This provides an appearance based rational and a simple measurement scheme for setting the parameters of these models. A reflectance model is also presented for use with so-called goniochromic surfaces such as metallic and pearlescent automotivepaint. This demonstrates that even complex surface reflection can often be captured with a few key measurements. Finally, the gloss based reflection models are combined with the goniochromic reflection model to render, using only four data values, a clear-coated automotive surface finish.