Rapid Acquisition of Specular and Diffuse Normal Maps from Polarized Spherical Gradient Illumination

Abstract
we estimate surface normal maps of an object from either its diffuse or specular reflectance using four spherical gradient illumination patterns. in constract to traditional photometric stereo, the spherical patterns allow normals to be estimated simultaneously from any number of viewpoints. 与传统的光度立体视觉相比，球面模式允许从任意角度同时估计法线 we present two polarized lighting techniques that allow the diffuse and specular normal maps of an object to be measured independently. for scattering materials, we show that the specular normal maps yield the best record of detailed surface shape while the diffuse normals deviate from 偏离 the true surface normal due to subsurface scattering, and that this effect is dependent on wavelength. we show several applications of this acquisition technique. first, we capture normal maps of a facial perfomance simultaneoulsy from several viewing positions using time-multiplexed 多路复用 illumination. second, we show that resolution normal maps based on the specular component can be used with structured light 3D scanning to quickly acquire high-resolutoin facial surface geometry using off-the-shelf 现成的 digital still cameras. finally, we present a realtime shading model that uses independently estimated normal maps for the specular and diffuse color channels to reproduce some of the perceptually important effects of subsurface scattering.