二维图形的外轮廓线搜索

本文针对CAPP中工序图生成的需要,在总结了前人在图形外轮廓线搜索方面所做研究的基础上,提出了一种改进的外轮廓线搜索求解思路,并运用AutoCAD提供的二次开发工具ADS,开发了相应的程序,该程序具有搜索自动化程度高、可操作性强、不易出错等特点,适合于任意复杂的图形。本文还就外轮廓线原始图形的恢复作了深入的探讨。     

VC++类和文件技术在AutoCAD二次开发中的应用

智能图形编程系统中,通常采用已有的几何建模工具构造实体几何模型图,然后再从图形标准交换文件中提取实体的几何数据进行分析和数控加工程序的自动编程.文中针对智能图形编程过程中图形数据的提取和动态管理这一关键技术,结合VC++中的类,分析了DXF文件中曲面、实体等数据的组织结构.对AutoCAD二次开发过程中数据接口文件中动态数据结构的设计及其层次模型和系统实现等进行了研究.结果说明提出的方法可以方便正确地实现数据的提取和表达,采用的动态内存管理可以有效地对数据进行管理.     

用Visual Basic对AutoCAD进行二次开发

一、引言AutoCAD一直是CAD市场中的主流产品。随着AutoCAD的日益普及，在其上进行二次开发的工具也不断更新。从早期的Auto Lisp、ADS、 DCL到现在流行的 Object ARX、ActiveX Automation、Visual Lisp，均可十分方便地对AutoCAD进行二次开发。本文主要讨论关于运用Visual Basic对AutoCAD基于ActiveX Automation的二次开发技术。选用 ActiveX有两个原因，一是因为Visual Basic的普及性与易用性，二是采用这种方法进行二次开发可方便地实现与其它图形软件的接口，如与SolidWorks实现实体造型与二维绘图的结合，以及根据用…     

VC＋＋类和文件技术在AutoCAD二次开发中的应用

智能图形编程系统中，通常采用已有的几何建模工具构造实体几何模型图，然后再从图形标准交换文件中提取实体的几何数据进行分析和数控加工程序的自动编程。文中针对智能图形编程过程中图形数据的提取和动态管理这一关键技术，结合VC＋＋中的类，分析了DXF文件中曲面、实体等数据的组织结构。对AutoCAD二次开发过程中数据接口文件中动态数据结构的设计及其层次模型和系统实现等进行了研究。结果说明提出的方法可以方便正确地实现数据的提取和表达，采用的动态内存管理可以有效地对数据进行管理。     

应用VBA技术进行AutoCAD二次开发

在AutoCAD制图应用过程中,需要开发一些符合用户需求的AutoCAD工具。VBA是一种对AutoCAD进行二次开发的灵活手段、应用VBA技术控制在AutoCAD环境中绘图,探讨它在AutoCAD二次开发中,VBA程序语句设计的基本步骤、具体实现过程．达到绘制所需要AutoCAD图形的目的.     

基于图形理解的预算工程量提取算法

分析了建筑图样（施工图）视图表达和图形理解的特点，基于工程量相关图形信息中各类图形实体的信息理解关系，提出了关联、特征实体的概念；给出施工图中工程量相关信息图形理解策略，并将图形理解的方法应用于预算工程的自动提取，为实现建筑CAD与概预算一体化提供新的途径；以土石方工程量为例，给出了工程量相关信息理解、搜索和识别算法。     

二次开发AutoCAD的消隐功能

AutoCAD作为优秀的图形设计软件平台，由于其良好的二次开发性能，在国内工程设计行业已经得到广泛运用。在程序设计中，灵活地运用AutoCAD提供的命令、系统变量、已定义的函数，往往可以解决许多难以解决的问题，起到事半功倍的效果。在机械、工程设计中常碰到消隐的问题，需要搜索图形的外边界，生成外边界，形成遮挡消隐。巧妙地利用AutoCAD提供的BOUNDARY命令进行编程，可以对任何具有封闭外边界图形，生成由Lwpolyline（多段线）构成的封闭的外边界,然后再利用AutoCAD在附赠程序中提供Wipeout命令通过封闭的多段线生成遮挡…     

AutoCAD实体曲面边界信息的提取及应用

一、前言AutoCAD在我国企业中普及率较高,其强大的绘图、编辑功能使许多设计人员甩掉了图板,提高了设计效率。笔者利用AutoCAD的ObjectARX二次开发环境所自带的边界表述库对零件实体的边界曲面信息进行提取分析,生成零件加工的刀具路径,并验证刀具位置。二、ObjectARX中的边界表述库AutoDesk公司为用户提供了一个强有力的二次开发环境——ObjectARX,利用C及C++语言的高效性,进行底层操作,扩充了AutoCAD的应用范围。ObjectARX自带的边界表述库（AcBr库）能对实体的边界进行访问,它可以处理三维实体、形体和面域等实体…     

AutoCAD2000电气图元菜单生成及与数据库的链接

本文基于AutoCAD2000对微机电气绘图进行了二次开发，阐述了电气图元菜单的生成方法及实施步骤，探讨了图形实体结构及附加属性与外部数据库的连接，说明其实现的原理及关键技术。     

面向异形切割的数控自动编程系统的开发

一、引言 异形切割是利用水切割机、雕刻机等专用切割机对异形金属板材、玻璃、布料、大理石等多种异形材料进行切割、图案裁剪的一种加工方法.异形切割一般适用于平面切割,针对不同材料有其特殊的加工工艺.现有的绘图编程一体化CAD/CAM软件不能满足要求,而且价格昂贵.本系统是基于绘图软件二次开发工具的自动编程系统,它以AutoCAD为开发平台,以AutoCAD VBA和VB6.0为编程语言,实现了图形处理、自动编程等功能.     

嵌入式镜片磨边机镜框采集处理系统

镜片磨边机作为眼镜加工的重要设备,使用者和市场对其技术要求越来越高,在这种情况下研制了嵌入式镜片磨边机。磨边机的镜框采集处理系统使用CMOS图像传感器对眼镜框进行采样,再通过OV511图像传感器通过USB接口芯片传送到中心处理器S3C2410中,采样图像在S3C2410中经过数字图像二值化和边缘检测等处理,获得镜框边缘信息并求出其它镜框参数以便在其它加工环节上使用。     

一种三角网格模型的轮廓生成方法

从三维网格模型中提取轮廓信息是一个具有挑战性的过程。现有的方法一般是基于局部形状特征 分析,如曲面的曲率和相邻面法向之间的夹角,但其特性通常对模型中的局部特征变化敏感。为了解决这个问题, 提出一种基于三维形状几何近似的轮廓提取方法。利用完善的变分几何分割算法来得到一套完整的描述性特征曲 线,首先基于变分几何近似方法划分模型为若干分片;其次提取所有分片的内部特征曲线,并过滤较短的特征曲 线;然后将分片的边界曲线平滑化;最后合并分片边界曲线与特征曲线,并延伸曲线得到闭合的轮廓。该方法的 优点是：在几何近似的基础上结合特征提取方法,使轮廓能够体现三维形状的全局结构。通过在各类网格模型上 进行实验和比较表明,该方法在提取模型轮廓的正确性和完整性方面优于现有方法。     

Dual representation of spatial rational Pythagorean-hodograph curves

In this paper, the dual representation of spatial parametric curves and its properties are studied. In particular, rational curves have a polynomial dual representation, which turns out to be both theoretically and computationally appropriate to tackle the main goal of the paper: spatial rational Pythagorean-hodograph curves (PH curves). The dual representation of a rational PH curve is generated here by a quaternion polynomial which defines the Euler–Rodrigues frame of a curve. Conditions which imply low degree dual form representation are considered in detail. In particular, a linear quaternion polynomial leads to cubic or reparameterized cubic polynomial PH curves. A quadratic quaternion polynomial generates a wider class of rational PH curves, and perhaps the most useful is the ten-parameter family of cubic rational PH curves, determined here in the closed form.     

Feature-preserving T-mesh construction using skeleton-based polycubes

This paper presents a novel algorithm which uses skeleton-based polycube generation to construct feature-preserving T-meshes. From the skeleton of the input model, we first construct initial cubes in the interior. By projecting corners of interior cubes onto the surface and generating a new layer of boundary cubes, we split the entire interior domain into different cubic regions. With the splitting result, we perform octree subdivision to obtain T-spline control mesh or T-mesh. Surface features are classified into three groups: open curves, closed curves and singularity features. For features without introducing new singularities like open or closed curves, we preserve them by aligning to the parametric lines during subdivision, performing volumetric parameterization from frame field, or modifying the skeleton. For features introducing new singularities, we design templates to handle them. With a valid T-mesh, we calculate rational trivariate T-splines and extract Bézier elements for isogeometric analysis.     

The Frenet frame beyond classical differential geometry: Application to cartographic generalization of roads

The reconstruction of curves from their curvature is a problem not very well-solved in cartographic generalization of roads. Frenet’s formulas theoretically solve this problem. The result shows that there exists a curve (up to rigid motion) with prefixed curvature function and torsion. By the use of the curvature and torsion functions, in closed forms, it is possible to obtain many beautiful examples in connection with this classical construction. In the case of plane curves, the torsion is equal to zero and the curve is characterized by the curvature. Nevertheless, if our starting point is a discrete set of arc length curvature experimental measures, the application of the Frenet frame is not straightforward. This study aims to describe how to adapt the classical Frenet frame to more realistic contexts derived from practical requirements. Our approach is applied to numerical measures derived from roads defined by Spanish Cartography, more precisely, by the Mapa Topográfico Nacional 1:25.000 (MTN25). The method described will be used to obtain generalizations of the original road by performing a standard wavelet decomposition on the curvature before the application of the Frenet frame for plane curves.     

Motion design with Euler–Rodrigues frames of quintic Pythagorean-hodograph curves

The paper presents an interpolation scheme for G¹ Hermite motion data, i.e., interpolation of data points and rotations at the points, with spatial quintic Pythagorean-hodograph curves so that the Euler–Rodrigues frame of the curve coincides with the rotations at the points. The interpolant is expressed in a closed form with three free parameters, which are computed based on minimizing the rotations of the normal plane vectors around the tangent and on controlling the length of the curve. The proposed choice of parameters is supported with the asymptotic analysis. The approximation error is of order four and the Euler–Rodrigues frame differs from the ideal rotation minimizing frame with the order three. The scheme is used for rigid body motions and swept surface construction.     

Fundamental limitations on projective invariants of planar curves

In this paper, some fundamental limitations of projective invariants of non-algebraic planar curves are discussed. It is shown that all curves within a large class can be mapped arbitrarily close to a circle by projective transformations. It is also shown that arbitrarily close to each of a finite number of closed planar curves there is one member of a set of projectively equivalent curves. Thus a continuous projective invariant on closed curves is constant. This also limits the possibility of finding so called projective normalisation schemes for closed planar curves     

Frame detection using gradients fuzzy logic and morphological processing for distant color eye images in an intelligent iris recognition system

The capture of an eye image with the occlusion of spectacles in a non-cooperative environment compromises the accuracy in identifying a person in an iris recognition system. This is due to the obstruction of the iris by the frame which tends to produce an incorrect estimation of the initial center of the iris and the pupil during the iris segmentation process. In addition, it also causes incorrect localization of the upper eyelid during the process of iris segmentation and sometimes, the edges of the frame are wrongly identified as the edges of the upper eyelid. A frame detection method which involves the combination of two gradients, namely the Sobel operator and high pass filter, followed by fuzzy logic and the dilation operation of morphological processing is proposed to identify the frame on the basis of different frame factors in the capture of a distant eye image. In addition, a different color space is applied and only a single channel is used for the process of frame detection. The proposed frame detection method provides the highest frame detection rate compared to the other methods, with a detection rate of more than 80.0%. For the accuracy of the iris localization, upper eyelid localization and iris recognition system, the proposed method gives more than 96.5% accuracy compared to the other methods. The index of decidability showed that the proposed method gives more than 2.35 index compared to the existing methods.     

Flexible smoothing with periodic cubic splines and fitting with closed curves

An algorithm is presented for constructing a smoothing cubic spline with periodic end conditions. The Lagrangian multipliers for pointwise individual closeness of fit conditions serve as control parameters. Using this algorithm parametrically the fitting of given points in the plane or in the three-dimensional space by smooth closed curves can easily be established.     

Multiresolution for Closed Curves and Surfaces Using Wavelets

Multiresolution modeling is becoming a powerful tool for fast display, and geometric data compression and transmission of complex shapes. Most of the existing literatures investigating the multiresolution for B-spline curves and surfaces are concentrated on open ones. In this paper, we focus on the multiresolution representations and editing of closed B-spline curves and surfaces using wavelets. A repetition approach is adopted for the multiresolution analysis of closed B-spline curves and surfaces. Since the closed curve or surface itself is periodic, it can overcome the drawback brought by the repetition method, i.e. introducing the discontinuities at the boundaries. Based on the models at different multiresolution levels, the multiresolution editing methods of closed curves and surfaces are introduced. Users can edit the overall shape of a closed one while preserving its details, or change its details without affecting its overall shape.