This paper proposes a method for estimating a set of spectral-power distributions of an omnidirectional light distribution from images taken by a camera aimed at a mirrored ball. First, we introduce some measuring systems that are designed for acquiring ambient light at any location in natural scenes. Second, a mapping algorithm is determined between coordinates on the ball and light rays in the world. Then we create images representing the omnidirectional light distribution. Third, the illuminant spectral-power distribution is recovered using the RGB image data and the calibrated reflectance data of the ball. Fourth, a CG image is created using the estimated omnidirectional illuminant distribution and a spectral-reflectance model for various objects. An experiment is conducted in our university gym.
Shoji Tominaga, Norihiro Tanaka, "Spectral Measurement of Omnidirectional Light Distribution and Its Application to Image Rendering" in Proc. IS&T 11th Color and Imaging Conf., 2003, pp 30 - 35, https://doi.org/10.2352/CIC.2003.11.1.art00007