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.
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
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)
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)
End Using
'' Save the new objects to the database
acTrans.Commit()
End Using
End Sub
C#
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
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);
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
Sub MirrorObject()
' Create the polyline
Dim plineObj As AcadLWPolyline
Dim points(0 To 11) As Double
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
points(10) = 4: points(11) = 1
Set plineObj = ThisDrawing.ModelSpace. _
AddLightWeightPolyline(points)
plineObj.SetBulge 1, -2
plineObj.Closed = True
ZoomAll
' Define the mirror axis
Dim point1(0 To 2) As Double
Dim point2(0 To 2) As Double
point1(0) = 0: point1(1) = 4.25: point1(2) = 0
point2(0) = 4: point2(1) = 4.25: point2(2) = 0
' Mirror the polyline
Dim mirrorObj As AcadLWPolyline
Set mirrorObj = plineObj.Mirror(point1, point2)
mirrorObj.color = acBlue
ZoomAll
End Sub