像素与地图空间单位转换问题

<PRE><CODE><FONT color=#0000ff>Private Function</FONT></CODE> <FONT style="BACKGROUND-COLOR: #316ac5" color=#ffffff>ConvertPixelsToMapUnits</FONT>(pixelUnits <CODE><FONT color=#0000ff>As Double</FONT></CODE>) <CODE><FONT color=#0000ff>As Double
  Dim</FONT></CODE> realWorldDisplayExtent <CODE><FONT color=#0000ff>As Double
  Dim</FONT></CODE> pixelExtent <CODE><FONT color=#0000ff>As Long
  Dim</FONT></CODE> sizeOfOnePixel <CODE><FONT color=#0000ff>As Double
  Dim</FONT></CODE> pDT <CODE><FONT color=#0000ff>As</FONT></CODE> IDisplayTransformation
  <CODE><FONT color=#0000ff>Dim</FONT></CODE> deviceRECT <CODE><FONT color=#0000ff>As</FONT></CODE> tagRECT
  <CODE><FONT color=#0000ff>Dim</FONT></CODE> pEnv <CODE><FONT color=#0000ff>As</FONT></CODE> IEnvelope
  <CODE><FONT color=#0000ff>Dim</FONT></CODE> pActiveView <CODE><FONT color=#0000ff>As</FONT></CODE> IActiveView
  <CODE><FONT color=#0000ff>Dim</FONT></CODE> pMxDocument <CODE><FONT color=#0000ff>As</FONT></CODE> IMxDocument
  
  <CODE><FONT color=#008000>' Get the width of the display extents in Pixels</FONT></CODE>
  <CODE><FONT color=#008000>' and get the extent of the displayed data</FONT></CODE>
  <CODE><FONT color=#008000>' work out the size of one pixel and then return</FONT></CODE>
  <CODE><FONT color=#008000>' the pixels units passed in mulitplied by that value</FONT></CODE>

  <CODE><FONT color=#008000>' QI for the IMxDocument interface from ThisDocument</FONT></CODE>
  <CODE><FONT color=#0000ff>Set</FONT></CODE> pMxDocument = ThisDocument
  
  <CODE><FONT color=#008000>' QI for the IActiveView interface from the currently selected Map</FONT></CODE>
  <CODE><FONT color=#0000ff>Set</FONT></CODE> pActiveView = pMxDocument.FocusMap

  <CODE><FONT color=#008000>' Get IDisplayTransformation</FONT></CODE>
  <CODE><FONT color=#0000ff>Set</FONT></CODE> pDT = pActiveView.ScreenDisplay.DisplayTransformation

  <CODE><FONT color=#008000>' Get the device frame which will give us the number of pixels in the X direction</FONT></CODE>
  deviceRECT = pDT.DeviceFrame
  pixelExtent = deviceRECT.Right - deviceRECT.Left

  <CODE><FONT color=#008000>' Now get the map extent of the currently visible area</FONT></CODE>
  <CODE><FONT color=#0000ff>Set</FONT></CODE> pEnv = pDT.VisibleBounds
  
  <CODE><FONT color=#008000>' Calculate the size of one pixel</FONT></CODE>
  realWorldDisplayExtent = pEnv.Width
  sizeOfOnePixel = realWorldDisplayExtent / pixelExtent

  <CODE><FONT color=#008000>'Multiply this by the input argument to get the result</FONT></CODE>
  <FONT style="BACKGROUND-COLOR: #316ac5" color=#ffffff>ConvertPixelsToMapUnits</FONT> = pixelUnits * sizeOfOnePixel
<CODE><FONT color=#0000ff>End Function</FONT></CODE>
这是Map中像素转为地图单位的程序，可是在Scene中如何实现呢？</PRE>

高手们帮忙看看啊，急

没弄过