9、Edit Polylines编辑多段线
2D and 3D polylines,rectangles,polygons,donuts,and 3D polygon meshes are all polyline variants and are edited in the same way.
二维多段线和三维多段线、矩形、多边形、圆环以及三维多边形网格都是多段线的变体，可以使用相同的方法对其进行编辑。
AutoCAD recognizes both fit polylines and spline-fit polylines. A spline-fit polyline uses a curve fit,similar to a B-spline. There are two kinds of spline-fit polylines: quadratic and cubic. Both polylines are controlled by the SPLINETYPE system variable. A fit polyline uses standard curves for curve fit and utilizes any tangent directions set on any given vertex.
AutoCAD能够识别拟合多段线和样条曲线拟合多段线。样条曲线拟合多段线使用曲线拟合而成，类似于B样条曲线。有两种样条曲线拟合多段线：二次的和三次的，两种多段线均由系统变量SPLINETYPE控制。拟合多段线使用标准曲线利用在给定顶点设置切线方向拟合而成。
To edit a polyline,use the properties and methods of the Polyline,Polyline2d,or Polyline3d object. Use the following properties and methods to open or close a polyline,change the coordinates of a polyline vertex,or add a vertex:
使用Polyline对象、 Polyline2d对象或Polyline3d对象的属性和方法来编辑多段线。下列属性和方法用于开放或闭合多段线、改变多段线顶点坐标、增加顶点等：
Closed 属性
Opens or closes the polyline. 开放或闭合多段线；
ConstantWidth 属性
Sets the constant width for a lightweight and 2D polyline. 设置轻量级和2D多段线宽度常量；
AppendVertex 方法
Adds a vertex to a 2D or 3D polyline. 给2D或3D多段线增加顶点；
AddVertexAt 方法
Adds a vertex to a lightweight polyline. 给轻量级多段线增加顶点；
ReverseCurve 方法
Reverses the direction of the polyline. 掉换多段线方向；
Use the following methods to update the bulge or width of a polyline:
SetBulgeAt 方法
Sets the bulge of a light polyline,given the segment index. 给定线段索引，设置多段线的凸度；
SetStartWidthAt 方法
Sets the start width of a lightweight polyline,given the segment index. 给定线段索引，设置轻量级多段线的起始宽度；
Straighten方法
Straightens a 2D or 3D polyline. 拉直2D或3D多段线
For more information about editing polylines,see “Modify or Join Polyline” in theUser's Guide.
关于编辑多段线的更多内容，见AutoCAD用户指南中的“修改或连结多段线”。
Edit a polyline 编辑多段线
This example creates a lightweight polyline. It then adds a bulge to the third segment of the polyline,appends a vertex to the polyline,changes the width of the last segment,and finally closes the polyline.
本例创建一条轻量级多段线，然后将第三条线段变成曲线（添加凸度）、追加一个顶点、修改最后那条线段的宽度，最后闭合该多段线。
VB.NET
Imports Autodesk.AutoCAD.Runtime
Imports Autodesk.AutoCAD.ApplicationServices
Imports Autodesk.AutoCAD.DatabaseServices
Imports Autodesk.AutoCAD.Geometry
<CommandMethod("EditPolyline")> _
Public Sub EditPolyline()
'' Get the current document and database
Dim acDoc As Document = Application.DocumentManager.MdiActiveDocument
Dim acCurDb As Database = acDoc.Database
'' Start a transaction
Using acTrans As Transaction = acCurDb.TransactionManager.StartTransaction()
'' Open the Block table for read
Dim acBlkTbl As BlockTable
acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,_
OpenMode.ForRead)
'' Open the Block table record Model space for write
Dim acBlkTblRec As BlockTableRecord
acBlkTblRec = acTrans.GetObject(acBlkTbl(BlockTableRecord.ModelSpace),_
OpenMode.ForWrite)
'' Create a lightweight polyline
Dim acPoly As Polyline = New Polyline()
acPoly.AddVertexAt(0,New Point2d(1,1),0)
acPoly.AddVertexAt(1,2),0)
acPoly.AddVertexAt(2,New Point2d(2,0)
acPoly.AddVertexAt(3,New Point2d(3,0)
acPoly.AddVertexAt(4,New Point2d(4,4),0)
'' Add the new object to the block table record and the transaction
acBlkTblRec.AppendEntity(acPoly)
acTrans.AddNewlyCreatedDBObject(acPoly,True)
'' Sets the bulge at index 3
acPoly.SetBulgeAt(3,-0.5)
'' Add a new vertex
acPoly.AddVertexAt(5,0)
'' Sets the start and end width at index 4
acPoly.SetStartWidthAt(4,0.1)
acPoly.SetEndWidthAt(4,0.5)
'' Close the polyline
acPoly.Closed = True
'' Save the new objects to the database
acTrans.Commit()
End Using
End Sub
C#
using Autodesk.AutoCAD.Runtime;
using Autodesk.AutoCAD.ApplicationServices;
using Autodesk.AutoCAD.DatabaseServices;
using Autodesk.AutoCAD.Geometry;
[CommandMethod("EditPolyline")]
public static void EditPolyline()
{
// Get the current document and database获取当前文档和数据库
Document acDoc = Application.DocumentManager.MdiActiveDocument;
Database acCurDb = acDoc.Database;
// Start a transaction启动事务
using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
{
// Open the Block table for read以读打开块表
BlockTable acBlkTbl;
acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,
OpenMode.ForRead) as BlockTable;
// Open the Block table record Model space for write
// 以写打开块表记录模型空间
BlockTableRecord acBlkTblRec;
acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],
OpenMode.ForWrite) as BlockTableRecord;
// Create a lightweight polyline创建轻型多段线
Polyline acPoly = new Polyline();
acPoly.AddVertexAt(0,new Point2d(1,0);
acPoly.AddVertexAt(1,0);
acPoly.AddVertexAt(2,new Point2d(2,0);
acPoly.AddVertexAt(3,new Point2d(3,0);
acPoly.AddVertexAt(4,new Point2d(4,0);
// Add the new object to the block table record and the transaction
//将新对象添加到块表记录和事务
acBlkTblRec.AppendEntity(acPoly);
acTrans.AddNewlyCreatedDBObject(acPoly,true);
// Sets the bulge at index 3设置线段3的凸度
acPoly.SetBulgeAt(3,-0.5);
// Add a new vertex添加新顶点
acPoly.AddVertexAt(5,0);
// Sets the start and end width at index 4设置线段4的起止宽度
acPoly.SetStartWidthAt(4,0.1);
acPoly.SetEndWidthAt(4,0.5);
// Close the polyline闭合多段线
acPoly.Closed = true;
// Save the new objects to the database提交修改
acTrans.Commit();
}
}
VBA/ActiveX Code Reference
Sub EditPolyline()
Dim plineObj As AcadLWPolyline
Dim points(0 To 9) As Double
' Define the 2D polyline points
points(0) = 1: points(1) = 1
points(2) = 1: points(3) = 2
points(4) = 2: points(5) = 2
points(6) = 3: points(7) = 2
points(8) = 4: points(9) = 4
' Create a light weight Polyline object
Set plineObj = ThisDrawing.ModelSpace. _
AddLightWeightPolyline(points)
' Add a bulge to segment 3
plineObj.SetBulge 3,-0.5
' Define the new vertex
Dim newVertex(0 To 1) As Double
newVertex(0) = 4: newVertex(1) = 1
' Add the vertex to the polyline
plineObj.AddVertex 5,newVertex
' Set the width of the new segment
plineObj.SetWidth 4,0.1,0.5
' Close the polyline
plineObj.Closed = True
plineObj.Update
End Sub
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