基于ObjectARX 开发工程图模块的研究

三维实体建模在机械产品的设计过程中得到了广泛应用,但二维工程图仍 是当前指导生产和进行技术交流必不可少的文件。为了从三维实体模型快速得到二维工程 图,利用ObjectARX 二次开发工具,在AutoCAD 平台上开发工程图模块,实现了实体模型 向工程图的快速转化以及自动标注。工程图生成在模型空间,方便后续操作。通过实例证明 该工程图模块能够从特征实体模型中提取工程图的相关信息,快速生成二维工程图,大大提 高用户的工作效率。     

一种二维工程图向三维模型的尺寸映射算法

针对当前制造型企业内部存在二维工程图和三维CAD模型之间的数据共享问题,提出一种基于图匹配的二维工程图向三维CAD模型的尺寸映射算法,将二维工程图中的尺寸信息直接映射到对应的三维CAD模型上。首先将三维模型进行投影得到投影视图,然后将投影视图和二维工程图转化为一种空间关系图,对两个空间关系图进行图匹配,找出图元间的映射关系,并且利用工程图中尺寸标注的特点对算法进行改进,提高算法效率和可靠性。实验结果表明,该算法可以很好的实现二维工程图向三维CAD模型的尺寸映射。     

正轴测投影反求建模研究

论文应用投影变换方法建立正轴测投影数学求解模型,提出一般伸缩系 数方法,实现了反求正轴测投影图的真实尺寸,再进行三维实体建模,达到原始设计不受 计算机约束,充分发挥人脑的想象力之目的。根据有立体感的正轴测投影图反求真实尺寸 后进行实体建模,生成二维加工图,这些过程由计算机完成,使之更符合设计从三维开始 的本质。     

钢结构节点三维实体技术

针对钢结构节点设计和施工图绘制需要大量构造细节的问题,应用钢结构节点的三维实体技术,研发相应的钢结构后处理系统.采用模板的概念与方法表达各种形式的钢结构节点,用三维实体技术构造钢结构节点及构件的三维计算机模型.该系统作为钢结构专业CAD软件3D3S的核心技术已经成功应用于数千项实际工程的施工详图设计中,实用性很强.     

3D Icons and Architectural CAD

3D computer input has been a recurring challenge to engineers developing effective CAD systems. The approach adopted in this paper attempts to address a specific type of 3D input which is applicable to architecture and some engineering design tasks. In these processes, the object being designed is often an assembly of defined components. In a conventional graphics based CAD system these components are usually represented by graphical Icons which are displayed on the graphics screen and are arranged by the user. The system described here consists of 3D modelling elements which the user physically assembles to form his design. Each modelling element contains an element processor consisting of a machine readable label, data paths and control logic. The CAD system interrogates the elements. The logic within the element processors and the data paths are then used to interrogate other adjacent elements in the model. This system can therefore be considered as a "user generated""machine readable" modelling system. In an architectural application this provides the user with a system of 3D Icons with which to model and evaluate the built environment.     

基于Pro／E的机械产品设计

基于Pro／E特征建模、参数化、全数据相关的特点,不仅能实现零部件的参数化实体建模,也可以方便地建立从三维模型到二维工程图的转换,有效地缩短设计时间,提高设计效率与质量。通过对Pro／E特点的讨论,结合台式钻床产品设计实例,论述了Pro／E在机械产品设计中的应用。     

用圆锥曲面求解几何约束问题

通常大多数三维参数化CAD系统都只用平面和球面作为最基本的作图工具,这在某种程度上限制了三维参数化CAD系统的作图范围.通过引进一类新的作图工具,使得三维参数化CAD系统的作图范围得到扩大. 同时证明了一个三维几何图形可以用平面、球面和圆锥曲面构造出来的充分必要条件是这个三维几何图形可以用一个三角化的次数小于9的代数方程组来描述.通过引进圆锥曲面作为新的作图工具,著名的三维Appolonius作图问题可以被完全求解.     

基于哈希的二维工程 CAD 图纸检索技术

针对企业在设计创新过程中大量采用已有计算机辅助设计(CAD)图纸进行设计重 用的情况,提出了一种基于哈希的二维工程 CAD 图纸检索方法。首先基于环形分割算法提取 工程 CAD 图纸中每个组件对象几何特征;基于传统 LBP 算子提出了一种局部拓扑矢量量化模 式(T-LVQP),实现对各个组件拓扑特征的提取;然后基于协方差描述符融合几何特征和拓扑特 征,通过 LBG 算法将所有组件按照几何特征分组后得到工程 CAD 图纸的特征向量表达;最后 通过迭代量化哈希算法生成图纸的哈希序列。实验结果表明,该算法检索速度快、准确度高, 对于二维工程 CAD 图纸具有较好的检索效果。     

融合视觉认知的工程视图理解方法

基于人的理解过程和方法,文中提出了工程视图理解的新算法框架。它允许用户参与到理解过程中,在出现歧义时,根据人的视觉认知规律进行“猜测”和“推理”,可得到与人的理解结果更为一致的解,并允许加入剖视图的处理。该文着重介绍该方法的算法思想,以及基元的划分与生成、剖视图处理、视觉推理等关键算法步骤。     

AutoCAD三维实体图形生成二维图形的实现

计算机辅助设计(CAD)是计算机应用技术中一项重要的技术。在CAD领域中,技术人员利用专门的计算机辅助设计软件来制作表现物体几何特征。AutoCAD是新一代计算机辅助设计软件,其功能强大,使用方便的特点在多种工程设计中得到广泛的应用。AutoCAD有强大的三维功能,可以在三维空间中先建立模型并从不同角度观察和处理模型,从三维模型可以生成各个方向的视图。本文主要介绍在AutoCAD中使用相关命令完成三维实体图形生成二维图形的方法。     

“3D 机械制图”教学中提高学生读图能力的实践与思考

随着以三维实体结构的表达方式为主干,三维设计表达方法和二维工程图 表达方法并重的知识结构体系的教学改革的不断深入,越来越多的人开始了解它,相关文献 也逐渐增多。因为随着计算机科学技术的发展,计算机技术已逐渐渗透到其他科学当中,同 时使得社会的产业结构也在悄悄的发生着变化,工程制图作为一门古老的学科也迎接着新科 技时代到来所带来的变革。因此,为了顺应时代的发展,图学教育完成由二维投影表达三维 立体过渡到直接三维设计将是历史发展的必然趋势。 论文结合十多年来讲授“3D 机械制图”的实践,总结多年的教改实际,针对如何改善 学生空间想象能力,更好地完成三维到二维的过度这一问题,介绍了作者近年来的教学实践 与思考。     

Decomposition of complex line drawings with hidden lines for 3D planar-faced manifold object reconstruction

Three-dimensional object reconstruction from a single 2D line drawing is an important problem in computer vision. Many methods have been presented to solve this problem, but they usually fail when the geometric structure of a 3D object becomes complex. In this paper, a novel approach based on a divide-and-conquer strategy is proposed to handle the 3D reconstruction of a planar-faced complex manifold object from its 2D line drawing with hidden lines visible. The approach consists of four steps: 1) identifying the internal faces of the line drawing, 2) decomposing the line drawing into multiple simpler ones based on the internal faces, 3) reconstructing the 3D shapes from these simpler line drawings, and 4) merging the 3D shapes into one complete object represented by the original line drawing. A number of examples are provided to show that our approach can handle 3D reconstruction of more complex objects than previous methods.     

基于增强现实技术的工程图学移动端教学系统 设计与开发

依托当前快速发展的虚拟现实技术,以工程图学课程图感培养为目标,将增强现 实技术引入课程教学,开发以移动终端为应用平台的辅助教学系统,将真实场景中的平面视图 与虚拟三维立体模型相结合,通过视觉耦合叠加和增强交互操作突出体验的真实感,搭建起视 图与形体间的以图感意识为桥梁的高效转换通道,提升了抽象三维形体的可接受度。配合课程 讲解和课下辅导,学生能够有意识地强化图感在视图解读中的认知作用,该教学模式和资源的 改革探索将有助于推动新时期工程图学教学的发展。     

Parametric virtual laboratory development: A hydropower case study with student perspectives

In order to take advantage of trends such as genetic-design students need to be familiar, and comfortable, with the concept of parametric computer models and how their parameters relate to physical-forms. Virtual learning software can aid in creating that understanding and help support studies at all undergraduate levels in engineering design disciplines. As an example, hydropower rotors are complex and largely rely on computational analysis of geometries for single rotor types. That problem can be significantly overcome using a parametric algorithm capable of creating an almost-infinite variety of computer models. Therefore, this paper investigates the shared parametric properties of common crossflow hydropower rotor geometries, resulting in a generic model that is then used to illustrate application in real-time interactive virtual learning software capable of producing accurate stereoscopic images and stereolithography files for 3D printing, as well as linking to constructive solid geometry software for slower, but more detailed, analysis. A pilot survey of student attitudes to the virtual learning prototype and resulting geometries is then discussed, illustrating the potential for 3D graphics as an effective addition to virtual learning of parametric design methods, and giving initial direction for future work.     

Sketching 3D models with 2D interaction devices

The creation of a 3D shape using CAD tools, namely solid modelers, is difficult and time-consuming. Therefore, these systems are kept away from the conceptual phases of design, perhaps the most important in any product life cycle. The sketch is considered by many people as one of the fundamental techniques during a design's conceptual stages, as it enables high level design options to be explored at low cost. In general, this technique IS under-appreciated in the computer graphics world. In this paper, we present a system called IDeS that tries to combine simplicity and intuition while drawing, with the useful features of the solid modelers, for example, CSG operators.     

Recovering solid geometric object from single line drawing image

Many educational materials contain a lot of solid geometric figures. The solid geometric objects in these figures are usually drawn as 2D line drawings thus have lost their 3D information. This paper presents a method to recover the 3D information of the solid geometric object from single line drawing image taken from the geometric books, which would be used to help the users better present and understand the solid geometric object on their mobile devices. The main advantage of our method is the abilitYTo handle inaccurately processed sketches as opposed to the previous methods which require perfect line drawings as inputs. Our method consists of three main steps as follows. First, the sketch of the input line drawing image is automatically extracted and further represented as an undirected graph. Second, candidate 3D models from the pre-built 3D model database are found by graph similarity-based searching and sub-graph isomorphism matching. Third, for each candidate 3D model, the model parameters, the rotation and the translation aligning the model with the sketch are found by minimizing an objective function which is composed of the residuals between the vertices of the sketch and the 2D projections of the candidate model’s vertices, and an optimal reconstruction solution is further selected as the final result. Extensive experimental results demonstrate the effectiveness and robustness of our method for recovering the solid geometric object from single line drawing image.     

A Graphic Programming Environment Based on KAΔMOΣ

In this paper the design and development of a graphic programming system to be relied on KAΔMOΣ are described. The system architecture upresented together with the functionality of construction and manipulation of the geometric entities. The environment provides an homogeneous handling of both 2D and 3D objects, these last being represented in a complete solid modelling scheme. Handling is achieved through a set of operators designed to manipulate geometric entities in a way suitable to hide users the implementation details of the specific representation domain. Prolog has been used as a common language to implement both the geometric entities supported by a hierarchical construction and their shape constraints.     

从知识表示到表示:人工智能认识论上的进步

知识表示是对智能进行模拟的一个数学模型,然而它可以不是一个对智能本质的描述,特别是传统的符号主义知识表示离揭示人的智能行为发生的内在过程还有很大的差距,在神经科学和心理学的指导下,通过对智能行为的生理基础和心理过程的研究,遵循“解释智能”的思想,可以得到对知识的心智表示的新认识,这种表示观的不同,预示着人工智能方法论上的进步。