Shape from shading and polarization constrained by approximate shape

Abstract

We propose a method which estimates the surface normal from shading information and polarization information. Unlike photometric stereo techniques which use three lights, shape-from-shading uses a single light and is an ill-posed problem. Therefore, to uniquely determine the surface normal using a shape-from-shading method, additional assumptions or additional inputs are required. We use polarization for additional input, because polarization can constrain the surface normal. One example of common assumption is to limits the target object to be a single color, but such assumption restricts the application field. Therefore, we use an approximate shape of the object to solve this problem. Thanks to this approximate shape, we can estimate the surface normal of multi-colored object.