Edit Polylines

2D and 3D polylines, rectangles, polygons, donuts, and 3D polygon meshes are all polyline variants and are edited in the same way.

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.

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:

Closed property: Opens or closes the polyline.
ConstantWidth property: Sets the constant width for a lightweight and 2D polyline.
AppendVertex method: Adds a vertex to a 2D or 3D polyline.
AddVertexAt method: Adds a vertex to a lightweight polyline.
ReverseCurve: Reverses the direction of the polyline.

Use the following methods to update the bulge or width of a polyline:

SetBulgeAt: Sets the bulge of a light polyline, given the segment index.
SetStartWidthAt: Sets the start width of a lightweight polyline, given the segment index.
Straighten: Straightens a 2D or 3D polyline.

For more information about editing polylines, see “Modify or Join Polyline” in the User's Guide.

Edit a polyline

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.

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, 0, 0)

      acPoly.AddVertexAt(1, New Point2d(1, 2), 0, 0, 0)

      acPoly.AddVertexAt(2, New Point2d(2, 2), 0, 0, 0)

      acPoly.AddVertexAt(3, New Point2d(3, 2), 0, 0, 0)

      acPoly.AddVertexAt(4, New Point2d(4, 4), 0, 0, 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, New Point2d(4, 1), 0, 0, 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

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

  Document acDoc = Application.DocumentManager.MdiActiveDocument;

  Database acCurDb = acDoc.Database;

  // Start a transaction

  using (Transaction acTrans = acCurDb.TransactionManager.StartTransaction())

      // Open the Block table for read

      BlockTable acBlkTbl;

      acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId,

                                   OpenMode.ForRead) as BlockTable;

      // Open the Block table record Model space for write

      BlockTableRecord acBlkTblRec;

      acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace],

                                      OpenMode.ForWrite) as BlockTableRecord;

      // Create a lightweight polyline

      Polyline acPoly = new Polyline();

      acPoly.AddVertexAt(0, new Point2d(1, 1), 0, 0, 0);

      acPoly.AddVertexAt(1, new Point2d(1, 2), 0, 0, 0);

      acPoly.AddVertexAt(2, new Point2d(2, 2), 0, 0, 0);

      acPoly.AddVertexAt(3, new Point2d(3, 2), 0, 0, 0);

      acPoly.AddVertexAt(4, new Point2d(4, 4), 0, 0, 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, new Point2d(4, 1), 0, 0, 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();

VBA/ActiveX Code Reference