混合细分曲面尖锐和半尖锐特征生成

在实际细分曲面造型中，模型初始控制网格经常需要同时用含有三角形和四边形的混合网格来表示。本文主要研究基于三角形和四边形的混合细分曲面的尖锐、半尖锐特征的生成方法。提出一种基于局部修改混合细分规则，把混合细分曲面的尖锐、半尖锐特征生成方式统一起来的自适应细分方法。为了使得多条折痕在相交点是C^1连续，在靠近折痕交点附近运用四点插值细分方法。根据特征处的尖锐程度通过自适应混合细分来实现半尖锐特征效果。实例表明，本算法生成的混合细分曲面尖锐、半尖锐特征效果非常好。

Generation of Sharp and Semi-Sharp Features of Hybrid Subdivision Surfaces

The surface with a quad and triangle hybrid patch structure is often desirable in engineering surface modeling. Generation of sharp and semi-sharp features such as crease, cone and corner over the quad and triangle hybrid mesh is investigated. A method based on modifying hybrid subdivision masks is presented. The subdivision matrices on feature points are discussed. Algorithms for generating sharp and semi-sharp features on hybrid subdivision surface are unified. Result of semi-sharp feature is dominated by sharpness of feature on the adaptive hybrid subdivision surface. In order to generate the C 1 continuity cross of many creases in hybrid subdivision surface, four-point interpolatory subdivision scheme is applied for points near the cross. Examples show the effects of sharp and semi-sharp features generated by the method.