Create Regions (.NET)

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

C#

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

Sub AddRegion()
    ' Define an array to hold the
    ' boundaries of the region.
    Dim curves(0 To 0) As AcadCircle
 
    ' Create a circle to become a
    ' boundary for the region.
    Dim center(0 To 2) As Double
    Dim radius As Double
    center(0) = 2
    center(1) = 2
    center(2) = 0
    radius = 5#
    Set curves(0) = ThisDrawing.ModelSpace.AddCircle _
                                     (center, radius)
 
    ' Create the region
    Dim regionObj As Variant
    regionObj = ThisDrawing.ModelSpace.AddRegion(curves)
 
    ZoomAll
End Sub