Discrimination Of Junctions In Line Drawing Based On AutoCAD ObjectARX Redevelopment

With the development of science and technology, communication with the graphs between people and computers is being paid attention and on many occasions its importance is shown. In order to make the computer see and understand object's projection chart, we need to study computer interpretting projection chart's mechanism. Research results of computer's analysis, process and interpretation of the chart can be used for the Internet, people-machine communication interface of the CAD system, reverse engineering and computer vision system, shorten graph input time and alleviate people's workload in people-machine communication.This paper aims to study and discriminate the new junctions marker classification in curved objects chart markers given by French scholars Cooper. Its junctions representation classification have:terminal, C, curvature-L, L, 3-tangent, W Y, T,4-tangent, Xo, K,Ψ, Peak, Multi, Lo, X, etc. In this paper, a variety of comparatively detailed algorithms to discriminate this 16 kinds of common junctions in the line marks in the three-dimensional chart are presented, and the mathematical reasoning processes for each algorithm are given, and algorithms for judging the same junction type is compared to seek a more optimal algorithm. In the early validation part of the junctions' algorithms, Visual C++ 6.0 programs are used, and through inputting junctions' coordinates and the junctions' adjacent points' coordinates and outputting junctions' graphics and judging results consistency in the MFC interface, the feasibility of the algorithm is verified.Because the line marks in the three-dimensional chart are in the plane, AutoCAD is chosen to discriminate junctions' types in the line drawing markers. Through analyzing the requirement of the junctions' types discrimination in the line marks in the three-dimensional chart, the developed AutoCAD software's functions are further obtained definitely. And through the further understanding of the AutoCAD system structure and interface language and predecessors' related and experienced summaries in developing and expanding AutoCAD function, feasibility in the AutoCAD 2002 platform with development forms to solve junctions' types discrimination problem in the line drawing marker is concluded and the whole junctions' types discrimination system's overall design scheme and the corresponding various discrimination flowcharts are given. Through comparing and analyzing various AutoCAD development tools' characteristics and requirements of junctions' types discrimination in the AutoCAD 2002, the Visual C++ 6.0 as the platform, ObjectARX as a development tool is decided.While developing the junctions' types discrimination system and analyzing various junctions' component liners, classes corresponding to various liners are chosen, such as AcDbLine class, AcDbCurve class corresponding to straight lines and curves, and corresponding functions are chosen to get straight lines' and curves' start points and end points, such as using AcDbCurve class to define object, and functions getStartPoint () and getEndPoint () to obtain start and end points' coordinates. Besides getting start and end points, required points can be obtained through getting straight lines' and curves' feature points and other methods, such as using the function getOsnapPoints () to obtain ellipses' and elliptic curves' snap points. In all required points of a junction, junction's coordinates are obtained through comparison algorithm, and the junction's type can be discriminated through the rest known points' coordinates, the mathematical relationship between the junction's coordinates and others points' coordinates and curves' and the algorithm of lines' statistical number to classify junctions.In order to make the AutoCAD development expanded interface meet people's operation habit and be distinguished from original interface, besides customers use custom commands, function menu is added and the docked window in non-modal dialog style is created through ObjectARX development tools' MFC function.