Surface topography using shape-from-shading,

This paper demonstrates how a recently reported shape-from-shading scheme can be used to extract topographic information from 2D intensity imagery (Worthington and Hancock, IEEE Trans. Pattern Anal. Mach. Intell. 21 (1999) 1250}1267). The shape-from-shading scheme has two important features which enhance the recovered surface description. Firstly, it uses a geometric update procedure which allows the image irradiance equation to be satis"ed as a hard constraint. This not only improves the data closeness of the recovered needle map, but also removes the necessity for extensive parameter tuning. Secondly, we use curvature information to impose topographic constraints on the recovered needle map. The topographic information is captured using the shape index of Koenderink and van Doorn (Image Vision Comput. 10 (1992) 557}565) and consistency is imposed using a robust error function. We show that the new shape-from-shading scheme leads to a meaningful topographic labelling of 3D surface structures. Moreover, the resulting topographic information proves to be useful in a simple histogram-based object recognition scheme. ( 2001 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.