Estimation of shape, reflection coefficients and illuminant direction from image sequences

摘要

A comprehensive scene analysis algorithm that extracts object shape, reflection coefficients and illuminant direction from just sequential images expressed as luminance values is proposed. The proposed algorithm uses an optical model consisting of a light source, an object and a viewer. Within this framework, the algorithm allows for diffuse and specular reflection, variations in object reflection coefficients and shading. The first phase of the algorithm calculates three values: (1) the variation of inner product of illuminant direction and surface normal before and after motion, and (2) the variation of shading, as well as (3) the motion field. The second phase uses these values to recover not only object shape but also illuminant direction and reflection coefficients of the surface. The algorithm's performance is confirmed through computer simulation. The reflection coefficients and the light source direction are estimated accurately while the recovered shape contains some errors.