Improved shape-from-shading using Darboux smoothing

This paper describes a new surface normal smoothing process which can be used in conjunction with shape-from-shading. Rather than directly smoothing the surface normal vectors, we exert control over their directions by smoothing the field of principal curvature vectors. To do this we develop a topography sensitive smoothing process which overcomes the problems of singularities in the field of principal curvature directions at the locations of umbilics and saddles