变化光照目标图像合成的球调和方法

光照是真实感绘制技术中的一个关键因素。研究了朗伯反射的球调和表示，提出了一种基于球调和函数的任意光照目标图像生成方法。该方法在给定目标基图像及其对应光照属性的基础上，通过基图像数据矩阵的奇异值分解（SVD）分离场景环境光分量、反演计算场景反射率和表面法向量等。新光照条件下绘制图像时，采用四阶球调和函数拟合入射光和朗伯反射核计算直接光照；间接光照采用分离出的基图像环境光分量拟合。实验表明：该方法能够保证绘制精确度，适合复杂光照条件下的目标图像生成。

Spherical Harmonics Method for Object Image Synthesis under Changing of Illumination

Illumination is a key factor in Reality rendering.We research the spherical harmonics express of Lambert re- flection and propose a pure image based rendering method to synthesis image under arbitrary illumination condition based on spherical harmonics.In the method,Singular Value Decomposition (SVD) is used analytically to derive envi- ronment light part and properties of scenes from sample images,which are taken from the same view point under differ- ent point illumination condition.For Images rendering under novel lighting conditions,fourth order spherical harmonics is used to represent the illumination condition and reflectance kernel for direct illumination effect calculation:while indi- rect illumination one is added by environment light part derived before.Thus the method cuts the time complexity down fiercely while holding on a high accuracy simultaneously.So feature of this method is that it supplies a good algorithm to synthesis image in complex illumination environment.