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—变动产品模型及其研究内容   总被引:2,自引:2,他引:8  
变动产品模型是从现有的产品数据模型中归纳出来的一类新的产品数据理论模型,具有许多新的性能特点,是新一代CAD/CAM系统产品数据模型的核心。  相似文献
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Automatic surface generation in computer aided design   总被引:1,自引:1,他引:1  
A technique for smoothly blending algebraic surfaces and a language for syntactic specification of objects are developed. Their use in automated design is illustrated by a gate valve example in which all fillets, edge roundings and joining surfaces are automatically constructed. The resulting object has an internal representation that is particularly amenable to interactive editing.This work was supported in part by the National Science Foundation under grant ECS 83-12096 and MCS 82-17996  相似文献
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Display of profiled sweep objects   总被引:1,自引:1,他引:0  
A class of free-form solids called profiled sweep objects is defined by four parametric curves: a 2D contour (cross-section), a 3D trajectory (spine), and two profile curves, which control the scaling of the contour as it moves along the trajectory. Subclasses of this are profiled prisms, which have a linear trajectory, and profiled generalized cylinders, which have an arbitrary 3D trajectory. First an exact definition of profiled sweep object, is presented and their relation with common sweep objects is described. Then a method is given for the construction of planar approximations of these objects that can be used for fast display generation. Finally, ray-tracing algorithms are given that directly use the exact definition for high-quality display.  相似文献
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任意多边形的Delaunay三角剖分   总被引:1,自引:1,他引:65  
任意多边形的三角剖分是计算机图形学领域中的一个基本算法,其用途非常广泛,本文利用著名的Delaunay三角剖分的优化性质,提出了一个简洁、通用的任意多边形Delaunay三角剖分算法,并给出了该算法在有限元网络自动生成过程的应用。  相似文献
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Interactive Visualization of Implicit Surfaces with Singularities   总被引:1,自引:1,他引:1  
This paper presents work on two methods for interactive visualization of implicit surfaces: physically-based sampling using particle systems and polygonization followed by physically-based mesh improvement which explicitly makes use of the surface-defining equation. While most previous work applied to bounded manifolds without singularities and without boundary (topological spheres) we broaden the scope of the methods to include surfaces with such features, in particular cusp points and surface self-intersections. These aspects are not (yet) essential for computer graphics modelling with implicit surfaces but they naturally occur in simulations of interest in mathematical visualization. In this paper we use the Kummer family of algebraic surfaces as an example.  相似文献
8.
曲面实体造型中曲线和曲面交点的求解   总被引:1,自引:1,他引:4       下载免费PDF全文
求交是曲面实体造型系统中影响拼合算法效率和稳定性的重要因素,而求交算法又是和曲面的几何表示密切相关的。NURBS虽然能统一表示所有曲面,但却给二次曲面的求交带来了不必要的复杂性。二次曲面经常在机械零件的设计中被用来描述轴、孔、槽等几何特征,因此它们的求交算法应具有高精度、高效率和高稳定性。为此,对一种实用的二次曲面表示方法——几何法进行了深入研究后,给出了构成二次曲面轮廓的几种二次曲线和空间四次曲线与二次曲面交点的求法。  相似文献
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In the initial stage of ship design, designers represent geometry, arrangement, and dimension of hull structures, which correspond to product model information, with 2D geometric primitives such as points, lines, arcs, and drawing symbols on 2D drawings. However, designers must translate the product model information defined on the 2D drawings more intelligently in the following design stages. Thus, design semantics could be lost and design processes that follow could be delayed because of errors by mistranslating the information. Here, design semantics mean design intents of the designer, that is, functions and structures which the product must have.In this study, a semantic product model data structure of an initial ship hull structure was proposed, and a semantic product modeling system was developed based on the proposed data structure. The proposed data structure can store semantic product model information such as product design results with the use of 2D wire frame geometrical data, part attributes, and design knowledge. Hence, this information can be used to generate a 3D solid model and production material information for CAPP as needed.The applicability of the proposed data structure and the developed system was verified by applying them to the deadweight 300,000 ton of Very Large Crude oil Carrier’s product modeling procedure. The application results showed that the proposed data structure and the developed system can be efficiently used for overall initial ship design environment.  相似文献
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广州西塔钢结构深化设计CAD软件   总被引:1,自引:1,他引:0  
针对广州西塔外钢框筒节点的构造非常复杂,且现有国内外钢结构深化设计软件不能胜任其深化设计工作的问题,研究复杂节点在构造上的规律与特点,同时考察加工与安装要求,基于AutoCAD平台,以ObjectARX与VC 为工具,开发专用的深化设计CAD软件.该软件具备从三维实体建模到自动绘制加工图的完整功能,已成功应用于广州西塔钢结构的深化设计工作.  相似文献
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