Inverse Rendering

Rendered image by the recovered parameters

Original image
Material recovery of Translucent Object

Reference Image

Recovery of Color

Recovery of Refractive Index

Recovery of transmission coefficients

Recovery of specular reflectance and roughness

The result after the third recursive

Material properties include texture of a surface and some optical parameters of a scene such as reflectance and refractive index, and so on. Recovering material properties are referred to obtain these parameters from images and a geometric model of a scene. Some algorithms have been developed for opaque objects. Our work focuses on translucent objects. Compared with the traditional opaque objects, translucent objects have not only reflectance parameters, but also transparent parameters and refractive index as well. Due to the interaction of the parameters in the rendering, it's more difficult to recover them.

At Start, we investigate and present a new method for recovering material properties of crystal-like objects. First of all, the objects in the image are separated into two classes: the opaque objects and the translucent objects. For the translucent objects, by analyzing refractive phenomena, we propose a method to recover an approximation of the refractive index and transmission coefficients. First, obtain the refractive index with the minimum error of color variance by a certain step calculations and then iteratively recover the color parameters. Experiments show that our algorithms can be completed in few iterative steps, and recovery error is very small. With the recovered material properties, the scene can be rendered under novel lighting or viewing conditions, and it can also be rendered when new objects are added into the scene.

Further, we investigate how to recover materials of translucent objects. Translucent objects have not only reflective coefficient but also transmission coefficient and refractive index. Here a new algorithm is presented to recover all these parameters iteratively. According to the interrelation and interaction of the parameters, we identify the sequence of parameters in the recovery and design an effective algorithm to get the parameters of the translucent objects under complex environment illumination. Furthermore, we do some experiments to validate the feasibility.


  1. Yan-kui Sun, Xi-peng Tong, Wei Wang, Hong-chuan Yu. Refractive Index and Transmission Coefficient Recovery Algorithm of Crystal-like Objects, Proceedings of the 9th international conference on Computer Aided Design and Computer Graphics, 525-530, 2005

  2. 卜海亮, 孙延奎,唐泽圣. 复杂环境光照下的半透明材质恢复算法.计算机辅助设计与图形学学报. Vol.18, No. 15,2006, 638-643
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