中文摘要：

针对动车组大模型实时绘制困难的问题，提出一种基于零件包围盒中心点的LOD自动生成方法与一种基于面向装配和维修重要性的实时自适应绘制方法．通过保留CAD装配树信息，以零件包围盒中心点为LOD中心点转换CAD大模型为虚拟装配、虚拟维修LOD模型，实现了大模型的LOD绘制．在上述LOD模型基础上，根据装配、维修对象的重要性，动态地调整LOD分辨率等级，实现了LOD实时自适应绘制．实验结果表明：采用文中方法生成的大型模型能完整保留CAD装配树，并可在普通计算机上实现实时的自适应绘制．

英文摘要：

In order to solve real-time rendering of massive models, an automatic LOD generation method based on bounding box center of parts and a real-time adaptive rendering method of assembly and maintenance are presented. By the method of building LOD center from the bounding box center of parts, the LOD model for vir- tual assembly and virtual maintenance comes from massive CAD model for keeping the CAD assembly tree, and rendering in real-time. On the basis of the LOD model,other method is used to adjust LOD levels according to the importance of the assembly and maintenance objects. The experiment result shows that the massive LOD model is rendered in interactive rate on a personal computer,and the CAD assembly tree are kept completely.