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排序方式: 共有65条查询结果,搜索用时 31 毫秒
1.
基于边界表达的ParaSolid与ACIS直接双向接口   总被引:8,自引:0,他引:8  
赵建军  王启付 《计算机工程》2004,30(8):40-41,141
提出了一种以边界表达Brep作为CAD软件问数据交流接口层的方法。针对目前Parasoljd和ACIS作为主流CAD几何核心这一事实,讨论了如何提取这两大几何核心的Brep,以及如何建立它们之间映射关系,继而通过重构Brep完成接口转换,并给出了实例验证该方法的可行性。  相似文献
2.
Differential Representations for Mesh Processing   总被引:6,自引:0,他引:6  
3.
基于径向基函数网络的隐式曲线   总被引:5,自引:1,他引:4  
将径向基函数网络与隐式曲线构造原理相结合,提出了构造隐式曲线的新方法,即首先由约束点构造神经网络的输入与输出,把描述物体边界曲线的隐式函数转化为显式函数,然后用径向基函数网络对此显式函数进行逼近,最后由神经网络的仿真曲面得到物体边界的拟合曲线.实验表明,基于径向基函数网络的隐式曲线具有很强的物体边界描述能力和缺损修复能力.  相似文献
4.
Construction and optimization of CSG representations   总被引:3,自引:0,他引:3  
Boundary representations (B-reps) and constructive solid geometry (CSG) are widely used representation schemes for solids. While the problem of computing a B-rep from a CSG representation is relatively well understood, the inverse problem of B-rep to CSG conversion has not been addressed in general. The ability to perform B-rep to CSG conversion has important implications for the architecture of solid modelling systems and, in addition, is of considerable theoretical interest.

The paper presents a general approach to B-rep to CSG conversion based on a partition of Euclidean space by surfaces induced from a B-rep, and on the well known fact that closed regular sets and regularized set operations form a Boolean algebra. It is shown that the conversion problem is well defined, and that the solution results in a CSG representation that is unique for a fixed set of halfspaces that serve as a ‘basis’ for the representation. The ‘basis’ set contains halfspaces induced from a B-rep plus additional non-unique separating halfspaces.

An important characteristic of B-rep to CSG conversion is the size of a resulting CSG representation. We consider minimization of CSG representations in some detail and suggest new minimization techniques.

While many important geometric and combinatorial issues remain open, a companion paper shows that the proposed approach to B-rep to CSG conversion and minimization is effective in E2, In E3, an experimental system currently converts natural-quadric B-reps in PARASOLID to efficient CSG representations in PADL-2.  相似文献

5.
Boolean set operations on non-manifold boundary representation objects   总被引:3,自引:0,他引:3  
For Boolean operations on geometric models, we have developed an intersection algorithm for non-manifold boundary models with vertices, linear edges, planar faces, and volumetric regions. The algorithm operates by intersecting entities in an ordered manner, from vertex to edge, then to face elements. Singular intersections are systematically handled by determining if an entity in one object is within a tolerance region of the entity in the other object. The algorithm performs Boolean operations between objects of different dimensionality as well as solids. An implementation of the proposed algorithm and the experimental results are briefly discussed.  相似文献
6.
Solid modeling of 4-axis wire EDM cut geometry   总被引:3,自引:0,他引:3  
NC verification has been widely used in milling and turning machining, but the implementation of NC verification for wire electrical discharge machine (wire EDM) has received little attention, made difficult by the characteristics of geometry cut by the thin wire. For an NC verification system, the speed and the accuracy of are two of the most critical issues. In this paper, a novel solid modeling method, which utilizes a dual quadtree structure and a boundary representation, is applied to modeling the parts cut by a wire EDM. In this implementation, two extended quadtrees on the top and bottom surfaces of the stock are first created. Special quadtree nodes are introduced into the dual quadtree structure to model the features associated with the almost coincident surfaces left by a thin wire. The region swept by a wire in each move is generated based on the diameter of the wire, spark gap size and the paths. The overall geometry of the part is represented by a boundary representation which is updated by means of efficient Boolean operations of extended quadtrees. The free-falling objects which may damage the machine tool can be detected. Dimensional inspection and feature detection can be made with the solid model representing the machined part. The system has demonstrated very promising speed and accuracy.  相似文献
7.
AutoCADObjectARX中实体B—REP的数据结构   总被引:3,自引:0,他引:3  
本文通过对AutoCAD中实体模型的边界表示法(B-REP)演变的论述,给出了ObjectARX中实体的半边数据结构。  相似文献
8.
图象边界的链码表示研究   总被引:3,自引:0,他引:3  
图象边界表示在模式识别、图象处理以及计算机视觉等领域扮演着十分重要的角色。本文研究了图象边界的链码表示,提出一种改进的链码表示方法。该方法通过二元组代替方向编号逐一编码方法,使用一个字节的高低位存取二元组的两个数值,节省了存储空间。理论分析和实验结果表明,与常用链码相比,该方法有效缩短了链码长度,能提高边界重绘速度,具有较强的实用性。  相似文献
9.
基于工程图的三维重建研究   总被引:3,自引:0,他引:3       下载免费PDF全文
龚洁晖  张 慧 《软件学报》2008,19(7):1794-1805
由二维工程图重建三维形体是一种快速的形体造型方法,已成为计算机图形学和人工智能领域的重要研究方向.立足于基于工程图的三维重建问题,分类总结了形体重建方法的研究成果,着重介绍了典型的重建算法.在比较了典型算法的适用范围的基础上,剖析了目前形体重建研究所面临的问题.最后,指出了基于工程图的三维重建算法进一步的研究方向.  相似文献
10.
快速成型中STL数据模型的B-Rep实体精确重建   总被引:2,自引:0,他引:2  
针对快速成型机广泛使用的STL数据模型,建立了STL文件拓扑重建的数据结构,给出了边界提取和面片分割的具体实施方法,实现了基于边界表示的实体建模.利用回转面的内在几何性质,提出了球面、柱面等规则曲面的识别方法,从而还原机械型面的原貌并实现规则型面的精确表示.对于自由曲面,采用调和映射参数化技术,实现了该类网格曲面的精确NURBS建模,给出了曲面片间保持G^1连续的优化拼接方法.实际的验证结果表明,重构的实体模型精度较高且便于系统间的数据交换,非常适于数控加工领域.  相似文献
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