Re: Here is a sample dataset

• To: visad-list@xxxxxxxxxxxxx
• Subject: Re: Here is a sample dataset
• From: "William L. Hibbard" <WHIBBARD@xxxxxxxxxxxxx>
• Date: Fri, 09 Apr 1999 16:38 CST

> and then ingested by the netCDF backend to VisAD, then it would appear
> as the following FlatField:
>
>     recnum -> (x, y, z, u, v, w)
>
> which is probably not what you want.  Undoubtably, you want a VisAD
> FlatField like the following:
>
>     (x, y, z) -> (u, v, w)
>
> Unfortunately, the "plain" netCDF conventions don't carry enough
> semantics with them to distinguish independent variables from dependent
> ones, which is why the first form of FlatField is created.
 
However, a FlatField with MathType:
 
    (recnum -> (x, y, z, u, v, w))
 
can still be displayed my mapping x -> XAxis, y -> YAxis,
z -> ZAxis, then perhaps u -> Flow1X, v -> Flow1Y, w -> Flow1Z
(this will make little vectors at each x, y, z location) or
some other set of mappings.
 
If you want to do something like contouring u, v and w values,
then you need a FlatField with MathType:
 
    (x, y, z) -> (u, v, w)
 
You could construct such a FlatField like this:
 
  FlatField field = ... // this has type (recnum -> (x, y, z, u, v, w))
  float[][] values = field.getFloats();
  RealTupleType range
    (RealTupleType) ((FunctionType) field.getType()).getRange();
  RealTupleType domain = new RealTupleType(
    (RealType) range.getComponent(0),
    (RealType) range.getComponent(1),
    (RealType) range.getComponent(2));
  RealTupleType new_range = new RealTupleType(
    (RealType) range.getComponent(3),
    (RealType) range.getComponent(4),
    (RealType) range.getComponent(5));
  float[][] samples = new float[3][];
  samples[0] = values[0];
  samples[1] = values[1];
  samples[2] = values[2];
  // WARNING: the Delaunay tetrahedralization used by this
  // Irregular3DSet constructor is slow for large numbers of samples
  Set set = new Irregular3DSet(domain, samples);
  FlatField new_field
    new FlatField(new FunctionType(domain, new_range), set);
  float[][] new_values = new float[3][];
  new_values[0] = values[3];
  new_values[1] = values[4];
  new_values[2] = values[5];
  new_field.setSamples(new_values);
 
There may be a few bugs in this, but its the general idea.
 
Cheers,
Bill
 
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
whibbard@xxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html