Ariel Tankus Nir A. Sochen Yehezkel Yeshurun Perspective Shape-from-Shading by Fast Marching. 43-49 2004 CVPR (1) http://csdl.computer.org/comp/proceedings/cvpr/2004/2158/01/215810043abs.htm db/conf/cvpr/cvpr2004-1.html#TankusSY04