Patent ID: 7940396

Claim:
An apparatus for measuring a spatially under-sampled Bidirectional Reflectance Distribution Function (BRDF) of a surface, the apparatus comprising: a first light source directed to illuminate the surface from a first illumination direction; a plurality of sensors positioned to receive light reflected by the surface, wherein the plurality of sensors comprises: a first sensor positioned to receive light reflected by the surface in a first reflectance direction; a second sensor positioned to receive light reflected by the surface in a second reflectance direction; and a third sensor positioned to receive light reflected by the surface in a third reflectance direction, wherein the first, second, and third directions are not coplanar; and a computer in communication with the plurality of sensors, wherein the computer is configured to convert light sensed by the plurality of sensors into a first appearance property of the surface considering the first, second, and third reflectance directions, wherein the first appearance property includes a plurality of directional responses of the surface, wherein each directional response is for a different wavelength or range of wavelengths, wherein the plurality of directional responses comprises a set of vectors, and wherein each of the set of vectors represents a vector sum of light measured over the plurality of reflectance directions at a given wavelength or wavelength range.