BRDF/BTF measurement device

Capturing surface appearance is important for a large number of applications. Appearance of real world surfaces is difficult to model as it varies with the direction of illumination as well as the direction from which it is viewed. Consequently, measurements of the BRDF (bidirectional reflectance distribution function) have been important. In addition, many applications require measuring how the entire surface reflects light, i.e. spatially varying BRDF measurements are important as well. For compactness we refer to a spatially varying BRDF as a BTF (bidirectional texture function). Measurements of BRDF and/or BTF typically require significant resources in time and equipment. In this work, a device for BRDF/BTF measurement is presented that is compact, economical and convenient. The device uses the approach of curved mirrors to remove the need for hemispherical positioning of the camera and illumination source. Instead, simple planar translations of optical components are used to vary the illumination direction and to scan the surface. Furthermore, the measurement process is fast because the device enables simultaneous measurements of multiple viewing directions.