Transpaency in 2DDisplay and Integer2DSet

Hi everybody:

I´m using VisAD to visualize radar and lightling data. Now I've inserted also a GIF image on the background by visad.data.gif.GIFForm. The image is apearing behind all the other data, as it shoud.

The problem is that I could not make the undefined radar data invisible (alpha =0). I´m using a Integer2DSet and setting the points outside the radar range to Float.NaN but these points apear on the display´s background color.

I also tried to map to RGBA instead of RGB but didn´t worked either.

Thanks already Cicero A. W. Z.