Spin-UP: Spin Light for Natural Light Uncalibrated Photometric Stereo
Authors: Zongrui Li, Zhan Lu, Haojie Yan, Boxin Shi, Gang Pan, Qian Zheng, Xudong Jiang

Natural Light Uncalibrated Photometric Stereo (NaUPS) relieves the strict environment and light assumptions in classical Uncalibrated Photometric Stereo (UPS) methods. However due to the intrinsic ill-posedness and high-dimensional ambiguities addressing NaUPS is still an open question. Existing works impose strong assumptions on the environment lights and objects' material restricting the effectiveness in more general scenarios. Alternatively some methods leverage supervised learning with intricate models while lacking interpretability resulting in a biased estimation. In this work we proposed Spin Light Uncalibrated Photometric Stereo (Spin-UP) an unsupervised method to tackle NaUPS in various environment lights and objects. The proposed method uses a novel setup that captures the object's images on a rotatable platform which mitigates NaUPS's ill-posedness by reducing unknowns and provides reliable priors to alleviate NaUPS's ambiguities. Leveraging neural inverse rendering and the proposed training strategies Spin-UP recovers surface normals environment light and isotropic reflectance under complex natural light with low computational cost. Experiments have shown that Spin-UP outperforms other supervised / unsupervised NaUPS methods and achieves state-of-the-art performance on synthetic and real-world datasets. Codes and data are available at https://github.com/LMozart/CVPR2024-SpinUP.