There is a lot of research in the Computer Vision literature on this topic and its generalization. One particularly prolific researcher on the subject is Jan Ko

There is a lot of research in the Computer Vision literature on this topic and its generalization. One particularly prolific researcher on the subject is Jan Koenderink[1]. Or search for "Shape from Shading" or "shape from occluding contours" [1]http://www.cs.rutgers.edu/~decarlo/readings/koenderink-percep84.pdf http://www.cs.rutgers.edu/~decarlo/readings/koenderink-perce...