An improved variational approach of shape-from-shading is proposed. A new objective functional is formulated using a reflectance map equation and an image gradient equation. The reflectance map equation is described by a hybrid reflectance model which is prone to reality. Since the gradients of images exhibit the detailed information of two-dimensional image
the new objective functional contains more information of three-dimensional surface than the objective functional formulated by only reflectance map equation. Then
an improved algorithm of shape-from-shading is proposed by using the variational principle. The accuracy of the proposed algorithm is improved evidently compared with the basic variational algorithm
and experiments on synthetic images of hemisphere show that the relative average error of the proposed algorithm is reduced by 13.45% under the same iteration times. Reconstruction results from real complicated images show that the proposed algorithm is more accurate than the basic variational algorithm in dealing with the details of the surface.
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