Create Composite Regions

You can create composite regions by subtracting, combining, or finding the intersection of regions or 3D solids. You can then extrude or revolve composite regions to create complex solids. To create a composite region, use the Boolean method.

When you subtract one region from another, you call the Boolean 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 floorplan, call the Boolean method from the outer boundary of the floor space and use the uncarpeted areas, such as pillars and counters, as the object in the Boolean parameter list.

Create a composite region

Sub Ch4_CreateCompositeRegions()

	' Create two circles, one representing a room,

	' the other a pillar in the center of the room

	Dim RoomObjects(0 To 1) As AcadCircle

	Dim center(0 To 2) As Double

	Dim radius As Double

	center(0) = 4

	center(1) = 4

	center(2) = 0

	radius = 2#

	Set RoomObjects(0) = ThisDrawing.ModelSpace. _

						 AddCircle(center, radius)

	radius = 1#

	Set RoomObjects(1) = ThisDrawing.ModelSpace. _

						 AddCircle(center, radius)

	' Create a region from the two circles

	Dim regions As Variant

	regions = ThisDrawing.ModelSpace.AddRegion(RoomObjects)

	' Copy the regions into the region variables for ease of use

	Dim RoundRoomObj As AcadRegion

	Dim PillarObj As AcadRegion

	If regions(0).Area > regions(1).Area Then

		' The first region is the room

		Set RoundRoomObj = regions(0)

		Set PillarObj = regions(1)

	Else

		' The first region is the pillar

		Set PillarObj = regions(0)

		Set RoundRoomObj = regions(1)

	End If

' Subtract the pillar space from the floor space to

	' get a region that represents the total carpet area.

	RoundRoomObj.Boolean acSubtraction, PillarObj

	' Use the Area property to determine the total carpet area

	MsgBox "The carpet area is: " & RoundRoomObj.Area

End Sub

Find the area of the resulting region with the Area property.