Variational Uncalibrated Photometric Stereo under General Lighting

Photometric stereo (PS) techniques nowadays remain constrained to an ideal laboratory setup where modeling and calibration of lighting is amenable. This work aims to eliminate such restrictions. To this end, we introduce an efficient principled variational approach to uncalibrated PS under general illumination, which is approximated through a second-order spherical harmonic expansion. The joint recovery of shape, reflectance and illumination is formulated as a variational problem where shape estimation is carried out directly in terms of the underlying perspective depth map, thus implicitly ensuring integrability and bypassing the need for a subsequent normal integration. We provide a tailored numerical scheme to solve the resulting nonconvex problem efficiently and robustly. On a variety of evaluations, our method consistently reduces the mean angular error by a factor of 2-3 compared to the state-of-the-art.