Identification of faces in a 2D line drawing projection of awireframe object

An important key to reconstructing a three-dimensional object depicted by a two-dimensional line drawing projection is face identification. Identification of edge circuits in a 2D projection corresponding to actual faces of a 3D object becomes complex when the projected object is in wireframe representation. This representation is commonly encountered in drawings made during the conceptual design stage of mechanical parts. When nonmanifold objects are considered, the situation becomes even more complex. This paper discusses the principles underlying face identification and presents an algorithm capable of performing this identification. Face-edge-vertex relationships applicable to nonmanifold objects are also proposed. Examples from a working implementation are given     

特征造型软件环境下图样表达方法研究

结合已经实行的“数字化产品数据定义通则”系列国家标准,对比二维图样 表达方法的优缺点,分析三维特征造型软件环境下的图样表达方式,研究了三维表达的基本 形式,指出基于特征造型软件环境开展工程制图教学,应在手工绘图条件下的各种二维表达 方式的基础上,充分发挥产品数字化数据定义的优势,采用最新国家标准,开展多种形式的 三维图样表达的教学。     

Labeling Line Drawings with Hidden-Part-Drawn of Planar Object with Trihedral Vertices

Although line drawings consist of only line segments on a plane, they convey much information about the three-dimensional object structures. For a computer interpreting line drawings, some intelligent mechanism is required to extract three-dimensional information from the two-dimensional line drawings. In this paper, a new labeling theory and method are proposed for the two-dimensional line drawing with hidden-part-draw of a three-dimensional planar object with trihedral vertices. Some rules for labeling line drawing are established. There are 24 kinds of possible junctions for line drawing with hidden-part-draw, in which there are 8 possible Y and 16 W junctions. The three problems are solved that Sugihara's line drawing labeling technique exists. By analyzing the projections of the holes in manifold planar object, we have put forward a labeling method for the line drawing. Our labeling theory and method can discriminate between correct and incorrect hidden-part-draw natural line drawings. The hidden-part-draw natural line drawings can be labeled correctly by our labeling theory and method, whereas the labeling theory of Sugihara can only label the hidden-part-draw unnatural line drawings in which some visible lines must be drawn as hidden lines, and some invisible lines must be drawn as continuous lines.     

基于MAR 的工程制图助学系统研究

在工程制图课程中根据二维图纸来构思三维形状,对于初学者来说有相当大的难 度。针对传统基于PC 端工程制图的多媒体辅助教学方式在交互性和易用性上的不足,研究基 于移动增强现实的工程制图助学系统。采用无标记识别技术实现工程图样与三维数字化模型的 自然交互,并在此基础上开发了一个功能齐全的助学APP,使用者可以通过手机摄像头扫描识 别二维工程图,在屏幕上叠加显示三维模型以及其他相关教学资源,用户可实时完成模型缩放、 旋转等操作,并且可对复杂的工程装配体模型进行拆卸和组装。实验结果表明,该系统不仅便 于学生自主学习,而且在一定程度上改善了工程制图课程的教学环境。     

具有相切面的曲面立体线画图标记研究

为了更好地理解三维景物，介绍了前人对线画图标记的研究成果，同时建立了一种标记具有相切面的曲面立体线画图的方法，并给出了具有相切面的曲面立体线画图的标记规则。由于线画图中的节点是由三面角构成的顶点的投影，因此对于画出隐藏线的具有相切面的曲面立体线画图，其合法的节点标记形式有38种，其中Y型节点有6种，W型节点有18种，V型节点有14种。新的标记方法适用于由平面立体和曲面立体组合而成的复杂立体线画图。     

与基于模型定义技术相融合的工程图学课程教学探讨

摘 要：针对工程图学课程教学,从工程应用角度介绍了产品定义技术所经历的 3 个阶段, 即二维设计二维出图、三维设计二维出图和全三维数字化定义,引出基于模型技术的起源与应 用发展。结合波音 787 飞机模型解析了基于模型定义数据集的组成和表达形式。引用航空标准 中几何尺寸与公差标注方法,以圆柱面为例,探讨了与基于模型定义技术相融合的工程图学课 程教学案例,对比分析了二维工程图和三维基于模型定义数据集的表达内容、表达形式和优缺 点。与基于模型定义技术相融合的工程图学课程教学,一方面可以增加课堂信息量、拓宽学生 的知识面,强化学生的工程基础,为后续专业课程学习和实际应用打下良好基础;另一方面也 可以激发学生的学习兴趣和科研兴趣,形成科研与教学之间的良性互动。     

智能装配机器人机械零件知识库的自动建立

为了实现智能装配机器人能够模拟人装配机械零件,系统应包含有关装配所必需的知识.利用这些知识,机器人自动编制装配工艺规程.并自动安排机器人的一系列控制命令.机械零件知识库是基于知识的智能装配机器人规划系统中不可缺少的知识.本文介绍了由机器人的视觉系统摄入机械零件图纸后,如何由摄入的二值化图形自动建立机械零件知识库.     

A multilevel graphics system based on top-down methodology

STRUKEDIT is an interactive graphics system based on top-down methodology. It is especially designed to manipulate very large drawings representing complex entities, such as electronic circuits or an organization chart.STRUKEDIT allows the user to create a drawing according to the principles of step-wise refinement and top-down design. At the highest level, there is a general representation of the object; this object may be divided into several parts, each of which may be drawn in more detail at the lower level. The process of refinement applies again to this level, and so on until all relevant details are included at the lowest level.STRUKEDIT is implemented in the MIRA-2D language, a graphical PASCAL extension based on abstract graphical types. It may be a useful tool in business administration, technical and industrial design, electronic design, and in all areas that involve the representation of complex objects or structures.     

Three-dimensional graph drawing

Graph drawing research has been mostly oriented toward two-dimensional drawings. This paper describes an investigation of fundamental aspects of three-dimensional graph drawing. In particular we give three results concerning the space required for three-dimensional drawings. We show how to produce a grid drawing of an arbitraryn-vertex graph with all vertices located at integer grid points, in ann×2n×2n grid, such that no pair of edges cross. This grid size is optimal to within a constant. We also show how to convert an orthogonal two-dimensional drawing in anH×V integer grid to a three-dimensional drawing with volume. Using this technique we show, for example, that three-dimensional drawings of binary trees can be computed with volume . We give an algorithm for producing drawings of rooted trees in which thez-coordinate of a node represents the depth of the node in the tree; our algorithm minimizes thefootprint of the drawing, that is, the size of the projection in thexy plane. Finally, we list significant unsolved problems in algorithms for three-dimensional graph drawing. This work was performed as part of the Information Visualization Group(IVG) at the University of Newcastle. The IVG is supported in part by IBM Toronto Laboratory.     

基于免疫遗传算法的工程图自动调优技术

针对目前三维模型参数化变型后,工程图自动生成方法中出现的视图布局 不合理、比例失调、标注混乱等问题,及现有调图技术的局限性,论文提出采用免疫遗传算 法对工程图进行优化调整。实现了基于模板参数化驱动后工程图的自动更新与视图布局、视 图比例及其各种标注位置等的优化调整。实验证明该方法可以实现智能化快速出图,保证设 计的准确性,提高设计效率和质量。     

基于约束关系的平面立体三维重建

提出一种基于约束的平面立体三维重建算法。该算法采用参数化方式来表示空间直线及其投影,这种参数化方式能满足数字图像中直线提取所需的唯一性、有界性及均匀性条件。依据平面立体投影线图的拓扑结构隐含的三维信息,建立平面立体上棱线、表面空间位置参数之间的约束方程,联立约束方程组求其最小二乘解,恢复出平面立体的三维结构。研究成果可用于计算机视觉和智能CAD系统。     

Thoughtful Drawings: A Computational Model of the Cognitive Nature of Children''s Drawing

An interpretation of children's drawing is presented that is based on active perception of the world and the construction of an equivalent self contained two-dimensional world. This model is implemented in a computer program called Rose (Representation Of Spatial Experience). Inspired by the drawings of young children, Rose simulates the perception of the general form and structure of three-dimensional computer models and constructs equivalent childlike two-dimensional representations from them. Rose serves to illustrate the plausibility of the constructive process as a model for real children's drawing and in addition serves as an alternative approach to traditional computer graphic rendering.     

Intelligent approaches for generating assembly drawings from 3-D computer models of mechanical products

In order to reduce the time of mechanical product design and ensure the high quality of their assembly drawings, this paper develops an intelligent approach for generating assembly drawings automatically from three-dimensional (3-D) computer assembly models of mechanical products by simulating the experienced human designer's thinking mode with the aid of computer graphics and knowledge-based expert system. The key issues include the strategies and methods for selecting the necessary views in an assembly drawing, determining necessary sectional views in each view, eliminating the unreasonable projective overlap of the components in each view, and minimizing the numbers of both the views in an assembly drawing and the sectional views in each view. Based on the approach, corresponding software prototype was developed. Finally, it is demonstrated, from an example of the fixture in a modularized drilling machine, that its assembly drawing was generated successfully using this intelligent software prototype.     

基于 MBD 的三维图样表达方式研究与系统实现

针对现有三维图样技术在实际应用中存在的主要问题,提出了设计视图、模型与 标注分区显示、集成标注等具体方法,解决了目前三维图样信息显示不清晰、无法满足复杂产 品信息定义需求等关键问题。结合数字化环境下产品信息表达与数据一致性等需求,采用信息 结构树保证了几何与非几何信息间的关联性。给出了三维图样系统的具体设计方案,以及相应 可视化功能的具体实现方法,实现了基于 ACIS 与 HOOPS 联合平台的三维图样软件系统开发, 在该系统中完成了典型零件的精度设计,验证了三维图样软件系统的实用性。     

现代化工设备三维可视化设计

介绍了三维可视化设计应用于现代化工设备设计的优越性和可行性,重点介绍三维可视化设计在塔板、填料、液体分布器、气体分布器和支撑结构等精馏塔内件中的应用。实践证明：三维可视化可以和强度、刚度、二维、重量、流体力学、数字化设计和制造相结合,从而,化工设备的设计过程从单一平面图转变为可视化的三维实体,使得设计过程更接近生产实际,缩短了产品设计周期,有效地降低成本。这项工作的推广将促进我国化工设备制造行业的信息化建设。     

宾州州立大学工程图学课程教学方法启发

为加快建设一流本科教育,以具有代表性的宾州州立大学工程图学为例,对教学 模式进行了深入对比与新方法探索研究。国外在教学内容上重视三维构形,关注细节;教学实 践上立足项目设计,理论与实践有机融合;教学手段能灵活综合运用胶片投影、多媒体和白板“三 位一体”。根据宾州州立大学工程图学注重教学内容与设计思维相结合的思想,结合国内教学现 状,潜心思索,进行了教学方法改革探索与实践。以装配图为引导,零件图为课程开展的思维 导图,对教学内容进行了模块化编排;同时制作了三维虚拟教具,提升学生的三维形体库储备, 强化读图能力;最后引导学生通过 SolidWorks 软件虚拟设计机械构件,并进行 3D 打印的延展 实践教学应用。相较目前国内多所高校“细而全”的输入式教学模式,强化了学生的表达技能训 练和主观能动学习,且学习成效显著,教学方法改革具有一定的有效性。     

Data integrity in an IGES description of turned part geometry

There is a growing interest in converting manually drawn engineering drawings into computer databases in a Computer Aided Design (CAD) format such as Initial Graphics Exchange Specification (IGES). This conversion is done by a high resolution scanning device. CAD drawings resulting from the scan-conversion process often contain discontinuities. A draftman using manual drafting equipment may adjust and reposition the ink pen for ease of drawing. This could cause breaks in the drawing, which, though unnoticeable to the human eye, are identified as discontinuities in the electronic scanning process. The subsequent CAD representation may then have broken geometries in place of continuous ones.

The work presented here is aimed at verifying the IGES file representing a scan-converted drawing. If any discontinuities are detected in the lines and arcs in the drawing, the breaks are mended. Algorithms are developed to identify and correct errors in the IGES files.

The algorithms are coded in Common LISP. The program runs on a VAX VMS system and can handle drawings of turned parts. This research is part of a larger project dealing with feature recognition of turned parts. Extension of the procedure to other geometries is straightforward. The program has been tested on some test drawings obtained from a scanning company. The results are very promising.     

基于工作过程的“机械图样识读与绘制”学习领域课程开发与设计

基于工作过程教学模式成为目前适应高职教育的有效模式。以机械设计 与制造专业基础课程“机械制图”与“计算机辅助设计与绘图”的整合为例,探讨对该课程学 科体系下的知识解构和基于工作过程导向重组,开发与设计、基于工作过程的“机械图样 识读与绘制”学习领域课程,使课程学习内容与工作内容良好对接,实现上岗工作“零适应 期”。     

建筑安装工程施工图设计与管理系统的实现

对安装工程施工图综合设计与管理系统的背景、总体设计作简要的介绍,由传统的二维图生成三维建筑构造图,建筑师可直接在三维空间设计水、风、电等安装子系统,进行碰撞检查和工程量统计,并对由三维模型图自动生成二维施工图的实现技术作较为详尽的叙述。     

工程设计中多图联动建模技术的研究与应用

工程设计中多图联动建模技术提供用户友好的工程设计空间,建立了工程原理图和多个工程布置图之间的信息关联。采用3D数据存储——2D图形可视转换技术,得到图形变换矩阵。把设备的各个视图的图块预存入图形库中,绘图时,设置相应的绘图图层,只要在布置图的一个视图中插入设备图,系统会在其他视图中自动插入相应的投影图形,并且当修改或者删除一个视图中的图形时,其他视图对应的图形也会自动完成相应的操作,实现了多个工程视图的联动。