Re: File Input

• To: Yuzhong Shen <shen@xxxxxxxxxxxxxxx>
• Subject: Re: File Input
• From: Bill Hibbard <hibbard@xxxxxxxxxxxxxxxxx>
• Date: Tue, 21 Mar 2000 12:40:46 -0600

Hi Yuzhong,

> I have a binary file containing 2-D scalar data in raw format, I'd like
> to know how to read the file. Is there a class in VisAD that can read
> such raw file directly, or do I have to write codes in Java to read the
> file by myself? Thanks a lot.

VisAD has file readers for a variety of specific formats
(e.g., netCDF, HDF-5, McIDAS, GIF, etc) but for a new format
you'll need to write some code to read the file and build
a VisAD data object.  2-D scalar data shouldn't be too
difficult.  For example, if you read your data into an
array named "data" of size "float[nx][ny]" then you'd
construct a VisAD Data object like this:

  RealType x = new RealType("x");
  RealType y = new RealType("y");
  RealType scalar = new RealType("scalar");
  RealTupleType domain = new RealTupleType(new Real[] {x, y});
  FunctionType function_type = new FunctionType(domain, scalar);
  Integer2DSet domain_set = new Integer2DSet(nx, ny);
  FlatField field = new FlatField(function_type, domain_set);
  float[][] field_data = new float[1][nx * ny];
  int k = 0;
  for (int j=0; j<ny; j++) {
    for (int i=0; i<nx; i++) {
      field_data[0][k] = data[i][j];
      k++;
    }
  }
  field.setSamples(field_data);

Then you can visualize the "field" data object with
something like this:

  DisplayImplJ3D display = new DisplayImplJ3D("scalar display");
  display.addMap(new ScalarMap(x, Display.XAxis));
  display.addMap(new ScalarMap(y, Display.YAxis));
  display.addMap(new ScalarMap(scalar, Display.ZAxis));
  DataReference ref = new DataReferenceImpl("scalar data");
  ref.setData(field);
  display.addReference(ref);

Which should make a simple terrain surface.  Lots of other
possibilities exist.

Cheers,
Bill
----------------------------------------------------------
Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738
http://www.ssec.wisc.edu/~billh/vis.html

• References:
  • File Input
    • From: Yuzhong Shen