为什么多边形边的延长线上的点与多边形用IntersectWith求交点时候返回值也不为空

clement

写了一个判断点是否在多边形的某条边上的程序，
以白色部分作为边界的时候，当取某条边延长线（红色部分）上的点时，

请问什么结果不正确？

Private Sub TestOnBoundary()
  Dim TestPoint As Variant
  Dim Util As AcadUtility
  Dim Entity As AcadEntity
  Dim PickPt As Variant
                                                              
  Set Util = ThisDrawing.Utility
  On Error GoTo Done
  Util.GetEntity Entity, PickPt, "Select region: "
  Do While (True)
    TestPoint = Util.GetPoint(, vbCrLf & "Test point: ")
    If IsPointOnBoundary(TestPoint, Entity) Then
      Util.Prompt (vbCrLf & "Point is on the boundary")
    Else
      Util.Prompt (vbCrLf & "Point is not on the boundary")
    End If
  Loop
Done:
End Sub

Private Function IsPointOnBoundary( _
                ByVal varPnt As Variant, _
                ByVal objBoundary As AcadEntity) As Boolean
  Dim objDoc As AcadDocument
  Dim objBlock As AcadBlock
  Dim objPnt As AcadPoint
  Dim varPnts As Variant
               
  Set objDoc = objBoundary.Document
  Set objBlock = objDoc.ObjectIdToObject(objBoundary.OwnerID)
 
  Set objPnt = objBlock.AddPoint(varPnt)
  varPnts = objPnt.IntersectWith(objBoundary, acExtendNone)
  IsPointOnBoundary = UBound(varPnts) > 0
  objPnt.Delete
               
End Function

雪山飞狐_lzh

点和实体怎么会有交点?

过该点做一条直线,如果直线和边界的交点在该点,则点在边界上

clement

点在边界上的时候当然就有交点了，如果没记错的话做射线那种方法测的是否在边界内部

雪山飞狐_lzh

仔细看一下我的方法！和以前的射线法不一样的

clement

明白了：）