use netcdf data and draw with visad problem..

Dear All:

 

 I have a netcdf file which have head file like this, and
 I want to get the data (rhum[0][1][][]) to draw with visad ...
 I don't know how to assign the section netcdf data to draw with visad.
 Is there any function I can use or any example which about get nectdf file,
 parse it and draw with visad..thanks a lot(special get section data)  
 
 netcdf rh {
  dimensions:
   time = 10 ;
   level = 8 ;
   lat = 73 ;
   lon = 144 ;
  variables:
   short rhum(time, level, lat, lon) ;//rhum[time][level][lat][lon]
    .....
    .....
    rhum:add_offset = 302.65f ;
    rhum:scale_factor = 0.01f ;
    .....
    .....
 }
 
 
 
 [code] 
 import visad.data.netcdf.*;
 
 Field imagesNC = null;
    DisplayImpl display = new DisplayImplJ3D("image display");
 
 try
    {
  imagesNC = (Field) plain.open("C:/tempNcfile/rh.nc");
 }
 catch (IOException exc)
    {
     System.out.println(exc);
        System.exit(0);
    }
   
    final Field image_sequence = imagesNC;   
    FunctionType image_sequence_type = (FunctionType) image_sequence.getType();
    FunctionType image_type = (FunctionType) image_sequence_type.getRange();
    RealTupleType domain_type = image_type.getDomain();
       
    // map image coordinates to display coordinates
    display.addMap(new ScalarMap((RealType) domain_type.getComponent(0), Display.XAxis));
    display.addMap(new ScalarMap((RealType) domain_type.getComponent(1), Display.YAxis));   
    display.addMap(new ScalarMap((RealType) domain_type.getComponent(2), Display.ZAxis));
   
    // map netcdf variable(varname) values to RGB
    RealTupleType range_type = (RealTupleType)image_type.getFlatRange();
    for(int nIdex = 0 ; nIdex < range_type.getNumberOfRealComponents() ; nIdex++)
    {
        String netcdf_varname = range_type.getComponent(nIdex).prettyString();
     if(netcdf_varname.equals(varname))
        {
           display.addMap(new ScalarMap((RealType) range_type.getComponent(nIdex), Display.RGB));
           break;
        }               
    }
   
    // link the Display to image_ref
    // display will update whenever image changes
    final DataReference image_ref = new DataReferenceImpl("image");
   
    image_ref.setData(image_sequence);    
    display.addReference(image_ref);            
    [/code]
   
    Can I use "import visad.data.netcdf.*;" functions in these package, or
    rewrite parse function in netcdf class package?
   
    Please Help me, thank you~~ :)
   
p.s I have other question with this..Any boby knows what's wrong ?
 why I run examples.VerySimple class which input val(x, y) netcdf file will be ok, but
 I run same function which input rhum(time, level, lat, lon) will get these exception..
   
    visad.BadMappingException: DisplayImpl.addMap: DisplayZAxis illegal for this DisplayRenderer
 at visad.DisplayImpl.addMap(DisplayImpl.java:1884)
 at visad.DisplayImpl.addMap(DisplayImpl.java:1846)
 at visad.util.DataUtility.makeSimpleDisplay(DataUtility.java:329)
 at examples.VerySimple.main(VerySimple.java:45)
 
 Thanks a lot :)