Create Composite Regions

Subtract regions

When you subtract one region from another, you call the BooleanOperation method from the first region. This is the region from which you want to subtract. For example, to calculate how much carpeting is needed for a floor plan, call the BooleanOperation method from the outer boundary of the floor space and use the non-carpeted areas, such as pillars and counters, as the object in the Boolean parameter list.

Unite regions

To unite regions, call the BooleanOperation method and use the constant BooleanOperationType.BoolUnite for the operation instead of BooleanOperationType.BoolSubtract. You can combine regions in any order to unite them.

Find the intersection of two regions

To find the intersection of two regions, use the constant BooleanOperationType.BoolIntersect. You can combine regions in any order to intersect them.

Create a composite region

The following example creates two regions from two circles and then subtracts the smaller region from the large one to create a wheel.

VB.NET

Imports Autodesk.AutoCAD.Runtime

Imports Autodesk.AutoCAD.ApplicationServices

Imports Autodesk.AutoCAD.DatabaseServices

Imports Autodesk.AutoCAD.Geometry

<CommandMethod("CreateCompositeRegions")> _

Public Sub CreateCompositeRegions()

  '' 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 two in memory circles

      Dim acCirc1 As Circle = New Circle()

      acCirc1.Center = New Point3d(4, 4, 0)

      acCirc1.Radius = 2

      Dim acCirc2 As Circle = New Circle()

      acCirc2.Center = New Point3d(4, 4, 0)

      acCirc2.Radius = 1

      '' Adds the circle to an object array

      Dim acDBObjColl As DBObjectCollection = New DBObjectCollection()

      acDBObjColl.Add(acCirc1)

      acDBObjColl.Add(acCirc2)

      '' Calculate the regions based on each closed loop

      Dim myRegionColl As DBObjectCollection = New DBObjectCollection()

      myRegionColl = Region.CreateFromCurves(acDBObjColl)

      Dim acRegion1 As Region = myRegionColl(0)

      Dim acRegion2 As Region = myRegionColl(1)

      '' Subtract region 1 from region 2

      If acRegion1.Area > acRegion2.Area Then

          '' Subtract the smaller region from the larger one

          acRegion1.BooleanOperation(BooleanOperationType.BoolSubtract, acRegion2)

          acRegion2.Dispose()

          '' Add the final region to the database

          acBlkTblRec.AppendEntity(acRegion1)

          acTrans.AddNewlyCreatedDBObject(acRegion1, True)

      Else

          '' Subtract the smaller region from the larger one

          acRegion2.BooleanOperation(BooleanOperationType.BoolSubtract, acRegion1)

          acRegion1.Dispose()

          '' Add the final region to the database

          acBlkTblRec.AppendEntity(acRegion2)

          acTrans.AddNewlyCreatedDBObject(acRegion2, True)

      End If

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

      acCirc1.Dispose()

      acCirc2.Dispose()

      '' 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("CreateCompositeRegions")]

public static void CreateCompositeRegions()

  // 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 two in memory circles

      Circle acCirc1 = new Circle();

      acCirc1.Center = new Point3d(4, 4, 0);

      acCirc1.Radius = 2;

      Circle acCirc2 = new Circle();

      acCirc2.Center = new Point3d(4, 4, 0);

      acCirc2.Radius = 1;

      // Adds the circle to an object array

      DBObjectCollection acDBObjColl = new DBObjectCollection();

      acDBObjColl.Add(acCirc1);

      acDBObjColl.Add(acCirc2);

      // Calculate the regions based on each closed loop

      DBObjectCollection myRegionColl = new DBObjectCollection();

      myRegionColl = Region.CreateFromCurves(acDBObjColl);

      Region acRegion1 = myRegionColl[0] as Region;

      Region acRegion2 = myRegionColl[1] as Region;

      // Subtract region 1 from region 2

      if (acRegion1.Area > acRegion2.Area)

          // Subtract the smaller region from the larger one

          acRegion1.BooleanOperation(BooleanOperationType.BoolSubtract, acRegion2);

          acRegion2.Dispose();

          // Add the final region to the database

          acBlkTblRec.AppendEntity(acRegion1);

          acTrans.AddNewlyCreatedDBObject(acRegion1, true);

      else

          // Subtract the smaller region from the larger one

          acRegion2.BooleanOperation(BooleanOperationType.BoolSubtract, acRegion1);

          acRegion1.Dispose();

          // Add the final region to the database

          acBlkTblRec.AppendEntity(acRegion2);

          acTrans.AddNewlyCreatedDBObject(acRegion2, true);

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

      acCirc1.Dispose();

      acCirc2.Dispose();

      // Save the new object to the database

      acTrans.Commit();

VBA/ActiveX Code Reference