Offset Objects

Offsetting an object creates a new object at a specified offset distance from the original object. You can offset arcs, circles, ellipses, lines, lightweight polylines, polylines, splines, and xlines.

To offset an object, use the GetOffsetCurves method provided for that object. The function requires a positive or negative numeric value for the distance to offset the object. If the distance is negative, it is interpreted by AutoCAD as being an offset to make a “smaller” curve (that is, for an arc it would offset to a radius that is the given distance less than the starting curve's radius). If “smaller” has no meaning, then AutoCAD would offset in the direction of smaller X,Y,Z WCS coordinates.

For many objects, the result of this operation will be a single new curve (which may not be of the same type as the original curve). For example, offsetting an ellipse will result in a spline because the result does fit the equation of an ellipse. In some cases it may be necessary for the offset result to be several curves. Because of this, the function returns a DBObjectCollection object, which contains all the objects that are created by offsetting the curve. The returned DBObjectCollection object needs to be iterated for each object created and then be appended to the drawing database.

For more information about offsetting objects, see “Copy, Offset, or Mirror Objects” in the AutoCAD User's Guide.

Offset a polyline

This example creates a lightweight polyline and then offsets it.

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

<CommandMethod("OffsetObject")> _

  Public Sub OffsetObject()

  '' 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)

      acPoly.AddVertexAt(5, New Point2d(4, 1), 0, 0, 0)

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

      acBlkTblRec.AppendEntity(acPoly)

      acTrans.AddNewlyCreatedDBObject(acPoly, True)

      '' Offset the polyline a given distance

      Dim acDbObjColl As DBObjectCollection = acPoly.GetOffsetCurves(0.25)

      '' Step through the new objects created

      For Each acEnt As Entity In acDbObjColl

          '' Add each offset object

          acBlkTblRec.AppendEntity(acEnt)

          acTrans.AddNewlyCreatedDBObject(acEnt, True)

      Next

      '' 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;

[CommandMethod("OffsetObject")]

public static void OffsetObject()

  // 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);

      acPoly.AddVertexAt(5, new Point2d(4, 1), 0, 0, 0);

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

      acBlkTblRec.AppendEntity(acPoly);

      acTrans.AddNewlyCreatedDBObject(acPoly, true);

      // Offset the polyline a given distance

      DBObjectCollection acDbObjColl = acPoly.GetOffsetCurves(0.25);

      // Step through the new objects created

      foreach (Entity acEnt in acDbObjColl)

          // Add each offset object

          acBlkTblRec.AppendEntity(acEnt);

          acTrans.AddNewlyCreatedDBObject(acEnt, true);

      // Save the new objects to the database

      acTrans.Commit();

VBA/ActiveX Code Reference