Modeling Illumination Variation with Spherical Harmonics
The appearance of objects including human faces can vary dramatically with the lighting. We present results that use spherical harmonic illumination basis functions to understand this variation for face modeling and recognition, as well as a number of other applications in graphics and vision.
Ravi Ramamoorthi. "Modeling Illumination Variation with Spherical Harmonics". In Face Processing: Advanced Modeling Methods, pages 385–424. 2006.