Ronen Basri Weizmann Institute of Science Shading provides rich information about shape. Beginning with the seminal work of Horn shape recovery using shading information has become one of the pillars of computer vision. This talk will survey some of the fundamental problems and algorithms for utilizing shading, focusing on the case of lambertian objects illuminated by directional sources. In particular, the problems of shape from shading and photometric stereo will be introduced along with their solutions using fast marching and factorization. Finally, we will discuss the generalized bas relief reconstruction ambiguity.