4、c++ Arx二次开发创建多段线

一、本节课程

c++ Arx二次开发创建多段线

二、本节要讲解的知识点

如何应用C++ ARX二次开发创建多段线（AcDbPolyline、AcDb2dPolyLine、AcDb3dPolyline的使用）

三、具体内容

1、ARX提供了三种多段线相关的类：AcDbPolyline、AcDb2dPolyLine、AcDb3dPolyline。PLINE 创建的是AcDbPolyline，3DPOLY创建AcDb3dPolyline。创建一般的轻量多段线只需要调用AcDbPolyline的构造函数即可，创建矩形、正多边形、圆形、圆环对象，关键在于顶点和凸度的确定。

2、添加多段线对象的函数实现：

AcDbObjectId CPolylineUtil::Add(const AcGePoint2dArray &points,double width)

{

int numVertices=points.length();

AcDbPolyline *pPoly=new AcDbPolyline(numVertices);

for (int i=0;i<numVertices;i++)

{

pPoly->addVertexAt(i,points.at(i),0,width,width);

}

return CDwgDatabaseUtil::PostToModelSpace(pPoly);

}

AcDbObjectId CPolylineUtil::Add(const AcGePoint2d &ptStart,const AcGePoint2d &ptEnd,double width)

{

AcGePoint2dArray points;

points.append(ptStart);

points.append(ptEnd);

return Add(points,width);

}

AcDbObjectId CPolylineUtil::Add3dPolyline(const AcGePoint3dArray &points)

{

AcGePoint3dArray verts=points;

AcDb3dPolyline *pPoly3d=new AcDb3dPolyline(AcDb::k3dSimplePoly,verts);

return CDwgDatabaseUtil::PostToModelSpace(pPoly3d);

}

AcDbObjectId CPolylineUtil::AddPolygon(const AcGePoint2d &ptCenter,int number,double radius,double rotation,double width)

{

double angle=2*CMathUtil::PI()/(double)number;

AcGePoint2dArray points;

for (int i=0;i<number;i++)

{

AcGePoint2d pt;

pt.x=ptCenter.x+radius*cos(i*angle);

pt.y=ptCenter.y+radius*sin(i*angle);

points.append(pt);

}

AcDbObjectId polyId=Add(points,width);

AcDbEntity *pEnt=NULL;

if (acdbOpenObject(pEnt,polyId,AcDb::kForWrite)==Acad::eOk)

{

AcDbPolyline *pPoly=AcDbPolyline::cast(pEnt);

if (pPoly!=NULL)

{

pPoly->setClosed(Adesk::kTrue);

}

pEnt->close();

}

EntityUtil::Rotate(polyId,ptCenter,rotation);

return polyId;

}

AcDbObjectId CPolylineUtil::AddRectangle(const AcGePoint2d &pt1,const AcGePoint2d &pt2,double width)

{

double x1=pt1.x,x2=pt2.x;

double y1=pt1.y,y2=pt2.y;

AcGePoint2d ptLeftBottom(min(x1,x2),min(y1,y2));

AcGePoint2d ptRightBottom(max(x1,x2),min(y1,y2));

AcGePoint2d ptRightTop(max(x1,x2),max(y1,y2));

AcGePoint2d ptLeftTop(min(x1,x2),max(y1,y2));

AcDbPolyline *pPoly=new AcDbPolyline(4);

pPoly->addVertexAt(0,ptLeftBottom,0,width,width);

pPoly->addVertexAt(1,ptRightBottom,0,width,width);

pPoly->addVertexAt(2,ptRightTop,0,width,width);

pPoly->addVertexAt(3,ptLeftTop,0,width,width);

pPoly->setClosed(true);

return CDwgDatabaseUtil::PostToModelSpace(pPoly);

}

AcDbObjectId CPolylineUtil::AddPolyCircle(const AcGePoint2d &ptCenter,double radius,double width)

{

AcGePoint2d pt1,pt2,pt3;

pt1.x=ptCenter.x+radius;

pt1.y=ptCenter.y;

pt2.x=ptCenter.x-radius;

pt2.y=ptCenter.y;

pt3.x=ptCenter.x+radius;

pt3.y=ptCenter.y;

AcDbPolyline *pPoly=new AcDbPolyline(3);

pPoly->addVertexAt(0,pt1,1,width,width);

pPoly->addVertexAt(1,pt2,1,width,width);

pPoly->addVertexAt(2,pt3,1,width,width);

pPoly->setClosed(Adesk::kTrue);

return CDwgDatabaseUtil::PostToModelSpace(pPoly);

}

4、c++ Arx二次开发创建多段线-LMLPHP

四、总结

1、AUTOCAD的三种多段线对象：AcDbPolyline、AcDb2dPolyline、AcDb3dPolyline，我们重点实现了AcDbPolyline、AcDb3dPolyline。

2、如何创建多段线，利用多段线对象来创建正多边形、矩形、圆、圆弧（关键点在于顶点坐标的计算和顶点凸度的概念的掌握）。如果对凸度概念不是很清楚，自己可以用代码来验证。

3、腾讯课堂搜索云幽学院贡献相应的公开课和报名的收费课的上课源代码、上课笔记技术咨询指导。