Mirror Objects

Mirroring flips an object along an axis or mirror line. You can mirror all drawing objects.

To mirror an object, use the Mirroring function of a transformation matrix. This function requires a Point3d, Plane, or Line3d object to define the mirror line. Since mirroring is done with a transformation matrix, a new object is not created. If you want to maintain the original object, you will need to create a copy of the object first and then mirror it.

To manage the reflection properties of Text objects, use the MIRRTEXT system variable. The default setting of MIRRTEXT is On (1), which causes Text objects to be mirrored just as any other object. When MIRRTEXT is Off (0), text is not mirrored. Use the GetSystemVariable and SetSystemVariable methods to query and set the MIRRTEXT setting.

You can mirror a Viewport object in paper space, although doing so has no effect on its model space view or on model space objects.

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

Mirror a polyline about an axis

This example creates a lightweight polyline and mirrors that polyline about an axis. The newly created polyline is colored blue.

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

Imports Autodesk.AutoCAD.Geometry

<CommandMethod("MirrorObject")> _

Public Sub MirrorObject()

  '' 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)

      '' Create a bulge of -2 at vertex 1

      acPoly.SetBulgeAt(1, -2)

      '' Close the polyline

      acPoly.Closed = True

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

      acBlkTblRec.AppendEntity(acPoly)

      acTrans.AddNewlyCreatedDBObject(acPoly, True)

      '' Create a copy of the original polyline

      Dim acPolyMirCopy As Polyline = acPoly.Clone()

      acPolyMirCopy.ColorIndex = 5

      '' Define the mirror line

      Dim acPtFrom As Point3d = New Point3d(0, 4.25, 0)

      Dim acPtTo As Point3d = New Point3d(4, 4.25, 0)

      Dim acLine3d As Line3d = New Line3d(acPtFrom, acPtTo)

      '' Mirror the polyline across the X axis

      acPolyMirCopy.TransformBy(Matrix3d.Mirroring(acLine3d))

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

      acBlkTblRec.AppendEntity(acPolyMirCopy)

      acTrans.AddNewlyCreatedDBObject(acPolyMirCopy, 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("MirrorObject")]

public static void MirrorObject()

  // 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);

      // Create a bulge of -2 at vertex 1

      acPoly.SetBulgeAt(1, -2);

      // Close the polyline

      acPoly.Closed = true;

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

      acBlkTblRec.AppendEntity(acPoly);

      acTrans.AddNewlyCreatedDBObject(acPoly, true);

      // Create a copy of the original polyline

      Polyline acPolyMirCopy = acPoly.Clone() as Polyline;

      acPolyMirCopy.ColorIndex = 5;

      // Define the mirror line

      Point3d acPtFrom = new Point3d(0, 4.25, 0);

      Point3d acPtTo = new Point3d(4, 4.25, 0);

      Line3d acLine3d = new Line3d(acPtFrom, acPtTo);

      // Mirror the polyline across the X axis

      acPolyMirCopy.TransformBy(Matrix3d.Mirroring(acLine3d));

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

      acBlkTblRec.AppendEntity(acPolyMirCopy);

      acTrans.AddNewlyCreatedDBObject(acPolyMirCopy, true);

      // Save the new objects to the database

      acTrans.Commit();

VBA/ActiveX Code Reference