Shape understanding from Lambertian photometric flow fields

Abstract

A novel idea for the analysis of shape from reflectance maps is introduced. It is shown that local surface orientation and curvature constraints can be obtained at points on a smooth surface by computing the instantaneous rate of change of reflected scene radiance caused by angular variations in illumination geometry. The resulting instantaneous changes in image irradiance values across an optic sensing array of pixels constitute what is termed a photometric flow field. There is no correspondence problem with respect to obtaining the instantaneous change in image irradiance values between successive image frames. This is because the object and camera remain static relative to one another as the illumination geometry changes. Simulations show how photometric flow fields quantitatively determine local surface orientation from a known incident orientation of an illuminator, as well as determining incident illuminator orientation from a known local surface orientation. >