方差阴影图中的光渗现象消除算法  

Removal of Light Bleeding in Variance Shadow Maps

作　　者：薛盖超[1,2] 吕伟伟[1,2] 刘学慧[1] 

机构地区：[1]中国科学院软件研究所计算机科学国家重点实验室,北京100190 [2]中国科学院研究生院,北京100049

出　　处：《计算机辅助设计与图形学学报》2009年第2期165-171,共7页Journal of Computer-Aided Design & Computer Graphics

基　　金：国家自然科学基金(60573155,60473105)

摘　　要：方差阴影图算法使用概率的方法计算像素被遮挡的上限概率,通过对深度图滤波的方法来有效地减少阴影图算法中的走样问题,但在深度比较复杂的场景中方差阴影图算法会出现光渗现象,即在应该是阴影的区域却有了亮度.文中使用最小-最大阴影图来辅助消除方差阴影图中的光渗现象,在对深度纹理进行滤波的同时生成一个最小-最大阴影图;在实时绘制场景时,利用最小-最大阴影图来辅助判断当前片元是否完全处在阴影区域内部,由此生成更真实、更准确的阴影.该算法可以很容易地添加到已有的方差阴影图算法的片元处理程序中,并且不会对原有阴影的柔和边界以及绘制的帧率产生影响.Variance shadow maps algorithm adopts a probability method to estimate the up-bound of the probability of a pixel falling in shadow, it effectively reduces the aliasing in traditional shadow maps algorithm by filtering the shadow maps themselves. However, this method may cause light bleeding in scenes of high depth complexity, i.e. areas with umbra may receive some light. In this paper, we propose an algorithm of integrating min-max shadow maps with variance shadow maps to remove light bleeding. We construct min-max shadow maps when we filter variance shadow maps. During the rendering process, the min-max shadow maps are used to determine whether a fragment is in shadow or not. While our new approach generates more realistic and accurate shadows, it can be easily integrated into the fragment shader of variance shadow maps, and lay no influence on soft edges of shadows and fps.

关 键 词：阴影图 方差阴影图 光渗现象 预滤波 最小-最大阴影图 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]