Determining Cylindrical Shape from Contour and Shading

Abstract

This paper presents an algorithm for reconstructing the shape of a cylindrical object from contour and shading without knowing the surface albedo of the object or the lightiflg conditions of the scene. The input image is segmented into spherical, cylindrical, or planar surfaces by analyzing local shading. The cylindrical surface is characterized by the direction of the generating lines, determined from spatial derivatives in the image. The brightest generating line has strong constraints on the shading analysis on the cylindrical surface and leads to a simplification of the equation which represents the relation between the contour shape and the shading. Although there remains one degree of freedom between the surface normal of the base plane and the slant angle of the generating line, we can uniquely recover the cylindrical shape from this solution (up to reflection). Experimental results for synthetic image are shown.