Comparison of two shape-from-shading algorithms

Abstract

The shape-from-shading problem is known to be mathematically equivalent to a nonlinear first-order partial differential equation in surface elevation. Many different algorithms have been developed for determining shape-from-shading information. Horn proposed an algorithm for recovering height from a single image, on a data-directed curve in the (x,y) plane called a characteristic strip. He concentrated on the importance of singular points, surface models and occluding boundaries in providing initialization for the algorithm. Bruckstein proposed a new method for obtaining the height information considering the behavior of equal-height contours. When one such contour is available his proposed algorithm reconstructs all the equal-height curves of the surface of interest in a well-defined region. This paper compares these two algorithms experimentally. It was found that the Horn's characteristic strip algorithm appears to behave better.