求助：Engine中如何求一条线上任意两点的距离

<P>是两点在线上的距离。</P>

<PRE><FONT face=宋体>Public Function GetPointSide(pPolyline As IPolyline, pPoint As IPoint) As Boolean</FONT></PRE><PRE><FONT face=宋体>  Dim pCurve As ICurve</FONT></PRE><PRE><FONT face=宋体>  Dim outPoint As IPoint</FONT></PRE><PRE><FONT face=宋体>  Dim dAlong As Double, dFrom As Double</FONT></PRE><PRE><FONT face=宋体>  Dim bRight As Boolean</FONT></PRE><PRE><FONT face=宋体>  On Error GoTo EH</FONT></PRE><PRE><FONT face=宋体>  Set pCurve = pPolyline</FONT></PRE><PRE><FONT face=宋体>  pCurve.QueryPointAndDistance 0, pPoint, False, outPoint, dAlong, dFrom, bRight</FONT></PRE><PRE><FONT face=宋体>  GetPointSide = bRight</FONT></PRE><PRE><FONT face=宋体>  Set pCurve = Nothing</FONT></PRE><PRE><FONT face=宋体>  Set outPoint = Nothing</FONT></PRE><PRE><FONT face=宋体>  Exit Function</FONT></PRE><PRE><FONT face=宋体>EH:</FONT></PRE><PRE><FONT face=宋体>  MsgBox Err.Description</FONT></PRE><PRE><FONT face=宋体>End Function</FONT></PRE><PRE><p><FONT face=宋体> </FONT></p></PRE><PRE><FONT face=宋体>Sub test()</FONT></PRE><PRE><FONT face=宋体>  Dim pCol As IPointCollection</FONT></PRE><PRE><FONT face=宋体>  Dim pPolyline As IPolyline</FONT></PRE><PRE><FONT face=宋体>  Dim pPoint As IPoint</FONT></PRE><PRE><FONT face=宋体>  Dim i As Long</FONT></PRE><PRE><FONT face=宋体>  Dim dLength As Double</FONT></PRE><PRE><FONT face=宋体>  Dim dMaxLength As Double</FONT></PRE><PRE><FONT face=宋体>  dMaxLength = 0</FONT></PRE><PRE><FONT face=宋体>  For i = 0 To pCol.PointCount - 1</FONT></PRE><PRE><FONT face=宋体>    Set pPoint = pCol.Point(i)</FONT></PRE><PRE><FONT face=宋体>    dLength = GetPointPosition(pPolyline, pPoint)</FONT></PRE><PRE><FONT face=宋体>    If dLength > dMaxLength Then</FONT></PRE><PRE><FONT face=宋体>      dMaxLength = dLength</FONT></PRE><PRE><FONT face=宋体>    End If</FONT></PRE><PRE><FONT face=宋体>  Next i</FONT></PRE><PRE><FONT face=宋体>End sub</FONT></PRE>