Partial Entity Structure: A Compact Boundary Representation for Non-Manifold Geometric Modeling
Partial Entity Structure: A Compact Boundary Representation for Non-Manifold Geometric Modeling
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DOI：
10.1115/1.1433486
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发表时间：
2001-12
期刊：
影响因子：
--
通讯作者：
Sang-Hun Lee;Kunwoo Lee
中科院分区：
文献类型：
--
作者：
Sang-Hun Lee;Kunwoo Lee
ed models for conceptual design, mixed dimensional shapes for intermediate design steps, solid models for final design, mesh models on abstracted part shape for engineering analysis @3,4#, offset polyhedral models for tool path generation, and so on. • Boolean operations are closed in the representation domain of non-manifold models, unlike solid models @5–7#. The resultant shape of Boolean operations can be stored in a merged set, which contains not only the final Boolean result, but also a complete description of the input primitives, all of the intersections between them, and historical information @5,8,9#. By using this merged set, Brep models can be reshaped independently of their construction Boolean sequences @9#, and a feature-based modeler based on B-rep can be easily implemented @9,10#. • Traditional solid modeling functions such as sweeping and offsetting operations can be applied to different dimensional objects. For instance, a sheet model is generated by sweeping wire edges, a solid model is generated by sweeping a sheet model, and a mixed dimensional model is generated by sweeping a mixture of sheets and wireframes @11#. In addition, a thin-walled solid model can be generated efficiently by sheet modeling and offsetting @12#. The research concerned with the foundation of non-manifold modeling systems can be categorized into three groups: the design of topological representation schemes, the specification of a set of primitive topological operators, and the implementation of various high-level modeling capabilities like sweeping or Boolean operations. In the area of the design of topological representation schemes, several data structures such as the radial edge structure and the vertex-based representation have been suggested so far. These representations mainly focus on describing the sufficient a jacency relationships between topological entities in a nonmanifold model without considering the storage size. As a result, although they are quite efficient for topological queries, they are so redundant and complicated that the models occupy too much storage space. The storage requirement can be a critical problem, particularly for models in which topological data storage is more dominant than geometric data, such as tessellated or mesh models. For example, a cellular model composed of one million cubical cells requires more than 1 GB of storage only for its topological data if it is represented in the radial edge structure. Therefore, it is desirable to devise a new representation scheme that is more compact, but as efficient as the existing schemes. To fulfil this requirement, in this paper, we propose a compact as well as fast non-manifold boundary representation, called the partial entity structure~PES!. This representation allows the reduction of storage to approximately half that of the radial edge structure, while still allowing full topological adjacency relationships to be derived without loss of efficiency. In order to verify this improvement, the time and storage efficiency of the partial entity structure are investigated and compared with those of existing schemes. The rest of this paper is organized as follows: Section 2 describes the previous work on non-manifold data structures. Section 3 represents an approach to measure the time and storage efficiency of a data structure, and our method to design a more optimal data structure based on this measurement. Section 4 describes the partial topological entities that are introduced to repContributed by the Computer Aided Product Development ~CAPD! Committee for publication in the J OURNAL OF COMPUTING AND INFORMATION SCIENCE IN ENGINEERING. Manuscript received Aug. 2001; revised manuscript received Nov. 2001. Associate Editor: D. Anderson, K. Lee. 356 Õ Vol. 1, DECEMBER 2001 Copyright © 2001 by ASME Transactions of the ASME PROOF COPY 011104CIS
