IEEE Trans Pattern Anal Mach Intell. 2018 Jan;40(1):221-234. doi: 10.1109/TPAMI.2017.2655525. Epub 2017 Jan 19.
We propose uncalibrated photometric stereo methods that address the problem due to unknown isotropic reflectance. At the core of our methods is the notion of "constrained half-vector symmetry" for general isotropic BRDFs. We show that such symmetry can be observed in various real-world materials, and it leads to new techniques for shape and light source estimation. Based on the 1D and 2D representations of the symmetry, we propose two methods for surface normal estimation; one focuses on accurate elevation angle recovery for surface normals when the light sources only cover the visible hemisphere, and the other for comprehensive surface normal optimization in the case that the light sources are also non-uniformly distributed. The proposed robust light source estimation method also plays an essential role to let our methods work in an uncalibrated manner with good accuracy. Quantitative evaluations are conducted with both synthetic and real-world scenes, which produce the state-of-the-art accuracy for all of the non-Lambertian materials in MERL database and the real-world datasets.
我们提出了未校准的光度立体方法，以解决由于各向同性反射率未知而导致的问题。我们方法的核心是针对一般各向同性 BRDF 的“约束半向量对称”概念。我们表明，这种对称性可以在各种现实世界的材料中观察到，并且它导致了用于形状和光源估计的新技术。基于对称性的 1D 和 2D 表示，我们提出了两种用于表面法线估计的方法；一种方法侧重于在光源仅覆盖可见半球时准确恢复表面法线的仰角，另一种方法则在光源也不均匀分布的情况下进行全面的表面法线优化。所提出的稳健光源估计方法对于我们以高精度进行非校准的方法也起着至关重要的作用。使用合成和真实场景进行了定量评估，这为 MERL 数据库和真实世界数据集的所有非朗伯材料都产生了最先进的精度。
