三维船舶模型边界表示转构造表示方法  

A Method for Transforming B-Rep of 3D Ship Models into CSG

作　　者：太志伟 张兴龙 尹晓龙 沈恩亚 王建民[1] Tai Zhiwei;Zhang Xinglong;Yin Xiaolong;Shen Enya;Wang Jianmin(School of Software,Tsinghua University,Beijing 100084;Haihe Lab of ITAI,Tianjin 300459)

机构地区：[1]清华大学软件学院,北京100084 [2]先进计算与关键软件海河实验室,天津300459

出　　处：《计算机辅助设计与图形学学报》2023年第12期1851-1862,共12页Journal of Computer-Aided Design & Computer Graphics

基　　金：国家重点研发计划(2021YFB3302401);先进计算与关键软件海河实验室重点项目(XCHK20210102).

摘　　要：模型数据表示是CAD几何引擎的基础,边界表示(B-Rep)和构造实体几何(CSG)表示是常用的2种模型数据表示方法,随着混合建模的发展,B-Rep和CSG混合建模开始应用于船舶等模型量大的场景,其中B-Rep与CSG实体的互相转换是一个关键性功能.针对类型多样的基本实体的B-Rep转CSG问题,设计了解析B-Rep几何结构并根据拓扑结构组合为CSG实体的转换流程.针对复杂实体的B-Rep转CSG问题,根据凹凸性将实体划分为不同类型的区域,将区域的边界作为切割环,据此提出了切割环识别算法.基于切割环识别,设计了二叉分解树进行实体分解和CSG树生成流程.对15种基本实体以及4个复杂模型的若干B-Rep实体,测量了其转换为CSG实体的转换误差和转换时间.实验结果表明,模型尺寸归一化后,文中方法可以在0.05%模型尺寸的误差范围内完成B-Rep实体向CSG实体的转换,并已支撑船舶产品设计系统(SPD)的部件小样建模平台的模型轻量化功能.Model data representation is the foundation of the CAD geometry engine.The Boundary Representation(B-Rep)and Constructive Solid Geometry(CSG)representations are two commonly used model data representation methods.With the development of hybrid modeling,B-Rep and CSG hybrid modeling has been applied to large-scale models such as ships and the conversion between B-Rep and CSG is a key function.For the B-Rep to CSG conversion of primitives,a process was designed to parse the geometry structures in a B-Rep entity and combine them into a CSG primitive based on the topological structures.For conversion of complex entities,faces in a B-Rep entity are divided into different regions based on its convexity,and the boundary of each region is a cutting loop.Then a cutting loop recognition algorithm is proposed.Based on the cutting loop recognition results,a binary decomposition tree is designed for entity decomposition and CSG tree generation process.Fifteen types of basic entities and four complex models are used to make several B-Rep entities,and the conversion errors and time costs are measured.Experimental results show that the proposed method can achieve B-Rep to CSG conversion within an error range of 0.05%of the normalized model size,and has supported the model light-weighting function of the component sample modeling platform of the Ship Product Design System(SPD).

关 键 词：B-Rep转CSG 船舶CAD 实体分解 切割环 

分 类 号：TP391.41[自动化与计算机技术—计算机应用技术]