Edit Splines

You can edit the properties of an open or closed spline, and even convert it to a polyline. Use the following properties to open or close a spline, change its control points, or reverse the direction of a spline:

Degree: Returns the polynomial representation of the spline.
EndFitTangent: Returns the end tangent of the spline as a directional vector.
FitTolerance: Refits the spline to the existing points with new tolerance values.
NumControlPoints: Returns the number of control points for the spline.
NumFitPoints: Returns the number of fit points for the spline.
StartFitTangent: Returns the start tangent for the spline.

In addition, you can use the following methods to edit splines:

InsertFitPointAt: Adds a single fit point to the spline at a given index.
ElevateDegree: Increases the degree of the spline to the given degree.
GetControlPointAt: Gets the control point of the spline at a given index. (Gets one control point only.) The NumControlPoints property contains the number of control points of the spline.
GetFitPointAt: Gets the fit point of the spline at a given index. (Gets one fit point only. To query all the fit points of the spline, use the FitData property and then query the FitData object returned with its GetFitPoints member function.) The NumFitPoints property contains the number of fit points of the spline.
RemoveFitPointAt: Deletes the fit point of a spline at a given index.
ReverseCurve: Reverses the direction of a spline.
SetControlPointAt: Sets the control point of the spline at a given index.
SetFitPointAt: Sets the fit point of the spline at a given index. (Sets one fit point only. To change all the fit points of the spline, use the FitPoints property.)
SetWeightAt: Sets the weight of the control point at a given index.

Use the following read-only properties to query splines:

Area: Gets the enclosed area of a spline.
Closed: Indicates whether the spline is open or closed.
Degree: Gets the degree of the spline's polynomial representation.
IsPeriodic: Specifies if the given spline is periodic.
IsPlanar: Specifies if the given spline is planar.
IsRational: Specifies if the given spline is rational.
NumControlPoints: Gets the number of control points of the spline.
NumfFitPoints: Gets the number of fit points of the spline.

For more information about editing splines, see “Modify Splines” in the AutoCAD User's Guide.

Change a control point on a spline

This example creates a spline and then changes the first control point for the spline.

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

Imports Autodesk.AutoCAD.Geometry

<CommandMethod("EditSpline")> _

Public Sub EditSpline()

  '' 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 Point3d Collection

      Dim acPt3dColl As Point3dCollection = New Point3dCollection()

      acPt3dColl.Add(New Point3d(1, 1, 0))

      acPt3dColl.Add(New Point3d(5, 5, 0))

      acPt3dColl.Add(New Point3d(10, 0, 0))

      '' Set the start and end tangency

      Dim acStartTan As Vector3d = New Vector3d(0.5, 0.5, 0)

      Dim acEndTan As Vector3d = New Vector3d(0.5, 0.5, 0)

      '' Create a spline

      Dim acSpline As Spline = New Spline(acPt3dColl, _

                                          acStartTan, _

                                          acEndTan, 4, 0)

      '' Set a control point

      acSpline.SetControlPointAt(0, New Point3d(0, 3, 0))

      '' Add the new object to the block table record and the transaction

      acBlkTblRec.AppendEntity(acSpline)

      acTrans.AddNewlyCreatedDBObject(acSpline, 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("EditSpline")]

public static void EditSpline()

  // 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 Point3d Collection

      Point3dCollection acPt3dColl = new Point3dCollection();

      acPt3dColl.Add(new Point3d(1, 1, 0));

      acPt3dColl.Add(new Point3d(5, 5, 0));

      acPt3dColl.Add(new Point3d(10, 0, 0));

      // Set the start and end tangency

      Vector3d acStartTan = new Vector3d(0.5, 0.5, 0);

      Vector3d acEndTan = new Vector3d(0.5, 0.5, 0);

      // Create a spline

      Spline acSpline = new Spline(acPt3dColl,

                                   acStartTan,

                                   acEndTan, 4, 0);

      // Set a control point

      acSpline.SetControlPointAt(0, new Point3d(0, 3, 0));

      // Add the new object to the block table record and the transaction

      acBlkTblRec.AppendEntity(acSpline);

      acTrans.AddNewlyCreatedDBObject(acSpline, true);

      // Save the new objects to the database

      acTrans.Commit();

VBA/ActiveX Code Reference