Create Regions

Regions are added to a BlockTableRecord object by creating an instance of a Region object and then appending it to a BlockTableRecord. Before you can add it to a BlockTableRecord object, a region needs to be calculated based on the objects that form the closed loop. The CreateFromCurves function creates a region out of every closed loop formed by the input array of objects. The CreateFromCurves method returns and requires a DBObjectCollection object.

AutoCAD converts closed 2D and planar 3D polylines to separate regions, then converts polylines, lines, and curves that form closed planar loops. If more than two curves share an endpoint, the resulting region might be arbitrary. Because of this, several regions may actually be created with the CreateFromCurves method. You need to append each region created to a BlockTableRecord object.

Create a simple region

The following example creates a region from a single circle.

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

Imports Autodesk.AutoCAD.Geometry

<CommandMethod("AddRegion")> _

Public Sub AddRegion()

  '' 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 an in memory circle

      Using acCirc As Circle = New Circle()

          acCirc.Center = New Point3d(2, 2, 0)

          acCirc.Radius = 5

          '' Adds the circle to an object array

          Dim acDBObjColl As DBObjectCollection = New DBObjectCollection()

          acDBObjColl.Add(acCirc)

          '' Calculate the regions based on each closed loop

          Dim myRegionColl As DBObjectCollection = New DBObjectCollection()

          myRegionColl = Region.CreateFromCurves(acDBObjColl)

          Dim acRegion As Region = myRegionColl(0)

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

          acBlkTblRec.AppendEntity(acRegion)

          acTrans.AddNewlyCreatedDBObject(acRegion, True)

          '' Dispose of the in memory object not appended to the database

      End Using

      '' Save the new object 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("AddRegion")]

public static void AddRegion()

  // 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 an in memory circle

      using (Circle acCirc = new Circle())

          acCirc.Center = new Point3d(2, 2, 0);

          acCirc.Radius = 5;

          // Adds the circle to an object array

          DBObjectCollection acDBObjColl = new DBObjectCollection();

          acDBObjColl.Add(acCirc);

          // Calculate the regions based on each closed loop

          DBObjectCollection myRegionColl = new DBObjectCollection();

          myRegionColl = Region.CreateFromCurves(acDBObjColl);

          Region acRegion = myRegionColl[0] as Region;

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

          acBlkTblRec.AppendEntity(acRegion);

          acTrans.AddNewlyCreatedDBObject(acRegion, true);

          // Dispose of the in memory circle not appended to the database

      // Save the new object to the database

      acTrans.Commit();

VBA/ActiveX Code Reference