We present a practical photometric stereo method that works with general isotropic reflectances. Unlike previous approaches that use special hardware setups or dense measurements, our method only requires dozens of random yet known lighting directions. By spherically interpolating the light source directions to approximate the scene appearance under desired lighting directions, our method separately computes azimuth and elevation angles of the surface normal for each pixel. The effectiveness and accuracy of the proposed method are validated using a measured reflectance database with 100 isotropic materials and various real-world objects.
"Photometric stereo for general isotropic reflectances by spherical linear interpolation," Optical Engineering 54(8), 083104 (21 August 2015). https://doi.org/10.1117/1.OE.54.8.083104