Appearance sampling for obtaining a set of basis images for variable illumination
Appearance sampling for obtaining a set of basis images for variable illumination
复制标题
外观采样以获得一组可变照明的基础图像
DOI：
10.1109/iccv.2003.1238430
复制
发表时间：
2003
期刊：
影响因子：
--
通讯作者：
K. Ikeuchi
中科院分区：
文献类型：
--
作者：
Imari Sato;Takahiro Okabe;Yoichi Sato;K. Ikeuchi
先前的研究表明，物体在不同光照条件下的外观可以用低维线性子空间来表示。通过对不同光照条件下拍摄的大量图像进行主成分分析（PCA），可以得到一组跨越该线性子空间的基图像。虽然基于PCA的方法已经成功地用于不同光照条件下的目标识别，但人们对需要多少图像才能正确获得基本图像知之甚少。在这项研究中，我们提出了一种新的方法，可以从在点光源下拍摄的物体的输入图像中解析地获得任意照明下物体的一组基图像。我们工作的主要贡献在于，我们证明了一组光照方向可以根据物体的BRDF在角频域中的频谱来确定采样图像，这样一组谐波图像就可以基于球面谐波的采样定理解析地获得。此外，与之前提出的基于球面谐波的技术不同，我们的方法不需要物体的三维形状和反射特性来综合渲染物体的谐波图像。
Previous studies have demonstrated that the appearance of an object under varying illumination conditions can be represented by a low-dimensional linear subspace. A set of basis images spanning such a linear subspace can be obtained by applying the principal component analysis (PCA) for a large number of images taken under different lighting conditions. While the approaches based on PCA have been used successfully for object recognition under varying illumination conditions, little is known about how many images would be required in order to obtain the basis images correctly. In this study, we present a novel method for analytically obtaining a set of basis images of an object for arbitrary illumination from input images of the object taken under a point light source. The main contribution of our work is that we show that a set of lighting directions can be determined for sampling images of an object depending on the spectrum of the object's BRDF in the angular frequency domain such that a set of harmonic images can be obtained analytically based on the sampling theorem on spherical harmonics. In addition, unlike the previously proposed techniques based on spherical harmonics, our method does not require the 3D shape and reflectance properties of an object used for rendering harmonics images of the object synthetically.