Shape-from-shading using viewpoint-invariant principal curvatures

We use the viewpoint compensation method of Woodham (1994) to make improved estimates of the Hessian matrix from the Gauss map in shape-from-shading. We use the improved estimates to perform curvature sensitive surface-smoothing. Rather than directly smoothing the surface normal vectors, we exert control over their directions by smoothing the field of principal curvature directions. To do this we develop a topography sensitive smoothing process which overcomes the problems of singularities in the field of principal directions at the locations of umbilics and saddles.