Numerical Shape from Shading and Occluding Contours in a Single View
This report describes research done at the Artificial Intelligence Laboratory of the Massachusetts Institute of Technology. Support for the laboratory's artificial intelligence research is provided in part by the Office of Naval Research under Office of Naval Research contract N00014-77-C-0389. Fig. 2-A and Fig. 26 are used from "magnification" by David Scharf under permission of the author.
An iterative method of using occluding boundary information is proposed to compute surface slope from shading. We use a stereographic space rather than the more commonly used gradient space in order to express occluding boundary information. Further, we use "average" smoothness constraints rather than the more obvious "closed loop" smoothness constraints. We develop alternate constraints from the definition of surface smoothness, since the closed loop constraints do not work in the stereographic space. We solve the image irradiance equation iteratively using a Gauss-Seidel method applied to the constraints and boundary information. Numerical experiments show that the method is effective. Finally, we analyze SEM (Scanning Electron Microscope) pictures using this method. Other applications are also proposed.