The free-form light stage

We present the Free-form Light Stage, a system that captures the reflectance field of an object using a free-moving, hand-held light source. By photographing the object under different illumination conditions, we are able to render the object under any lighting condition, using a linear combination of basis images. During the data acquisition, the light source is moved freely around the object and hence, for each picture, the illuminant direction is unknown. This direction is estimated automatically from the images. Although the reflectance field is sampled non-uniformly, appropriate weighting coefficients are calculated. Using this system, we are able to relight objects in a convincing and realistic way.