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:
Opens or closes the polyline.
Sets the constant width for a lightweight and 2D polyline.
Adds a vertex to a 2D or 3D polyline.
Adds a vertex to a lightweight polyline.
Reverses the direction of the polyline.
Use the following methods to update the bulge or width of a polyline:
Sets the bulge of a light polyline, given the segment index.
Sets the start width of a lightweight polyline, given the segment index.
Straightens a 2D or 3D 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.
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
Using 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
End Using
'' 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
using (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();
}
}
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