Measuring BRDF using a single still digital camera

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.