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 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.
