实体的B-rep表示模型是一非常复杂的模型，要求能够表达出多面体各几何元素之间完整的几何和拓扑关系，并且允许对这种几何和拓扑关系进行修改.在B-rep表示中，体、面、边和顶点是最基本的几何元素，在实体的拼合、显示、分析计算或人机交互过程中-The B-rep solid representation model is a very complex model, requires the ability to express the polyhedron between the geometric elements of the complete geometry and topology, and allows for such changes the relationship between geometry and topology. In B-rep representation, body, face, edge and vertex is the most basic geometric elements, in the merging entities, display, analysis and calculation, or the process of human-computer interaction