Proceedings Article | 29 November 2011
KEYWORDS: Bidirectional reflectance transmission function, Cameras, Optical spheres, Light sources, Calibration, Digital cameras, Computer graphics, Image processing, Reflectivity, Sensors
BRDF (Bidirectional Reflective Distribution Function)is broadly used in many fields, such as physics, heat
transformation, remote sensing, and computer graphics. Traditional methods to measure BRDF are expensive for most
peoples, and image based approach becomes a novel direction. Until now, for such an image based system, at least a
video camera and a still camera are indispensible, and the operations are not easily carried out under a convenient
condition. In this paper, a method using only one still camera is proposed, with the help of a light source, a cylinder
support, and a sphere. The material to be measured is painted on the sphere, putting on the cylinder support painted with
BRDF- known material. Around the cylinder support, a simple control points nets are distributed. In the measurement
process, the light source and the support are fixed, operators goes around the sphere to obtain pictures at different view
angles and the rest work is finished automatically by a set of programs. The pictures are first processed by a
photogrammetric program to get the geometry in the scene, including the positions, directions, and the shapes of light
source, the support, the sphere, and the cameras. The BRDF samples are calculated from the image intensity and the
obtained geometric relations, which are approximated by a multivariable spline to get a full BRDF description. Three
different materials are tested with the method.
