Carlos Hernández George Vogiatzis Roberto Cipolla Shadows in Three-Source Photometric Stereo. 290-303 2008 ECCV (1) http://dx.doi.org/10.1007/978-3-540-88682-2_23 conf/eccv/2008-1 db/conf/eccv/eccv2008-1.html#HernandezVC08