Re: contouring plus a colored field of same quantity

Hi Stuart,

> Again working through Ugo Taddei's VisAd tutorial, in section 3.5
> (
> I am trying to modify the example program P3_05 to plot contours
> of one color on a color-filled background map of the same quantity.
> The program as given plots contours of temperature, and the contours
> are colored according to the underlying elevation. I want to have one color
> contours of temperature over a background colored by temperature value.
> Commenting out the     "display.addMap( elevMap );"
> I get white contours on a black background, which is fine.
> then using (in place of tempIsoMap),
>     tempMapRGB = new ScalarMap( temperature,  Display.RGB );
>     display.addMap( tempMapRGB );
> I get a colored field, colored according to temperature values. As expected.
> So I think I shall plot white contours over the colored temperature
> field, by using both tempIsoMap and tempMapRGB.  To my surprise
> I get colored contours, and no colored field at all.  Why?
> Why does adding a isocontour map means my surface gets
> destroyed, when I simply wanted to have the isolines on top of the
> surface?

The behavior of the default DataRenderers is to render either
contours or filled colors for a single FlatField (instead of
contours, you could also substitute flow vectors, shapes or

To do what you want with the default DataRenderers is a little
tricky.  You need to make a copy of 'FlatField vals_ff'
temperature values with a new RealType substituted for
temperature in its MathType (which is a FunctionType).
Something like this:

    . . .
    temperature_2 = new RealType("temperature_2");
    func_domain_range_2 = new FunctionType( domain_tuple, temperature_2);
    . . .
    vals_ff = . . .
    float[][] values = vals_ff.getFloats(false); // don't copy
    float[][] values_2 = {values[0]};
    FlatField vals_ff_2 = new FlatField(func_domain_range_2, domain_set);
    vals_ff_2.setSamples(values_2, false); // don't copy
    . . .
    // simple color fill with temperature_2 values
    display.addMap(temperature_2, Display.RGB);
    . . .
    DataReferenceImpl data_ref_2 = new DataReferenceImpl("data_ref_2");
    data_ref_2.setData( vals_ff_2 );
    . . .

Leave all the other logic alone, to get the iso-contours of
temperature values in vals_ff.  I have not tried this code,
but the basic idea should work.

Bill Hibbard, SSEC, 1225 W. Dayton St., Madison, WI  53706
hibbard@xxxxxxxxxxxxxxxxx  608-263-4427  fax: 608-263-6738