contouring plus a colored field of same quantity

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

Stu Wier

Stuart Wier                           UCAR Unidata Program Center
wier@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8659                              Boulder, CO 80307
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