Numerically modeling the interaction of light with materials is an essential step in generating realistic synthetic
images. While there have been many studies of how people perceive physical materials, very little work has been
done that facilitates efficient numerical modeling. Perceptual experiments and guidelines are needed for material
measurement, specification and rendering. For measurement, many devices and methods have been developed for
capturing spectral, directional and spatial variations of light/material interactions, but no guidelines exist for the
accuracy required. For specification, only very preliminary work has been done to find meaningful parameters for
users to search for and to select materials in software systems. For rendering, insight is needed on the perceptual
impact of material models when combined with global illumination methods.