三角形重建的几何阴影图算法  

Geometric Shadow Mapping via Triangle-Based Reconstruction

作　　者：杜文俊[1] 冯结青[1] 杨宝光[1] 沈笠[1] 

机构地区：[1]浙江大学CAD&CG国家重点实验室,杭州310058

出　　处：《计算机辅助设计与图形学学报》2016年第2期208-217,共10页Journal of Computer-Aided Design & Computer Graphics

基　　金：国家自然科学基金(61170138;61173128)

摘　　要：针对阴影图算法中的走样和深度偏移的问题,使用离散的场景原始三角面片来表示和记录阴影遮挡物的信息,提出一种几何阴影图算法.由于遮挡物的深度值能够通过这种原始的连续几何进行精确地重构,解决了透视走样和投影走样的问题;只需要一个相对较小、取值稳定的深度偏移值来获得较好的接触阴影效果,同时避免自阴影的问题;为了降低算法中三角形几何的冗余存储,提出一种基于GPU的几何缓存压缩算法作为算法的选项;最后使用一种打包的阴影计算算法来进一步降低算法的访存开销;为了解决几何信息不完整所造成的阴影瑕疵,对于这一类像素使用线性外插的算法来估计其深度值.实验结果表明,文中算法能够高效地绘制出高质量的阴影.In this paper, a geometric shadow mapping (GSM) algorithm is proposed to address the issues of shadow aliasing artifacts and depth bias in shadow mapping algorithm. In GSM, occluders are discretely repre-sented in terms of the original triangles of the scene. Both perspective and projective aliasings can be greatly re-duced due to the ac-curate reconstruction of the depth from continuous geometries. For a given scenario, a rela-tively small and constant depth bias can guarantee both faithful contact shadows and being free of the self-shadowing problem. Furthermore a GPU-based geometry buffer compression method is proposed to reduce the storage redundancy of triangles. Packet-based shadow evaluation is employed to further reduce the total memory fetch overhead of the algorithm. To remedy artifacts caused by inconsistent pixels, depth values are es-timated via linear extrapolations for such pixels. The experimental results demonstrate that the proposed GSM algorithm can generate high-quality hard shadows in real time.

关 键 词：阴影图 基于三角形的几何 几何阴影图压缩 深度外插 

分 类 号：TP391[自动化与计算机技术—计算机应用技术]