Surface bidirectional reflection distribution function and the texture of bricks and tiles.

We study and analyze properties underlying the visual appearance of materials such as the surface bidirectional reflection distribution function and texture. The spatial distribution of scattered light in relation to the incident light determines the surface appearance and can be partly specified by the bidirectional reflection distribution function, which is defined as the directionally dependent ratio of radiance to irradiance. We perform gonioradiometric measurements on samples of bricks and tiles. To describe the reflection mechanisms in the surfaces under study, we combine models of specular and diffuse reflectance from rough surfaces and fit them to the experimental data. We also collect images and determine the textural differences in the surface appearance, resulting from the variation in the illumination direction and the viewing directions.