Illumination Model

1. Dichromatic Reflection Model [1] [2] $I_i=\gamma_b C_i L_i R_{b,i}+\gamma_s C_i L_i R_{s,i}$, in which $i$ is the pixel index, $L$ is the global illumination, $C_i$ is the sensor sensitivity. The chromatic terms $R_b$ and $R_s$ account for body and surface reflection, which are only related to object material.

2. gray pixels: pixels with equal RGB values. detecting gray pixels in a color-biased image is not easy. [3]

3. albedo, shading, gloss [4] [5]

Reference

[1] Shafer, Steven A. “Using color to separate reflection components.” Color Research & Application 10.4 (1985): 210-218.
[2] Song, Shuangbing, et al. “Illumination Harmonization with Gray Mean Scale.” Computer Graphics International Conference. Springer, Cham, 2020.
[3] Qian, Yanlin, et al. “On finding gray pixels.” CVPR, 2019.
[4] Bhattad, Anand, and David A. Forsyth. “Cut-and-Paste Neural Rendering.” arXiv preprint arXiv:2010.05907 (2020).
[5] Yu, Ye, and William AP Smith. “InverseRenderNet: Learning single image inverse rendering.” CVPR, 2019.