Re: Another Alpha Question

Hi Kevin,

There may be some problems with alpha in a 2-D display, since
ZAxis is a bit artificial in 2-D. The Australian BOM does its
2-D actually in 3-D, but with PARALLEL_PROJECTION and setting
the MouseHelper to disallow 3-D rotations. That way they can
explicitly control the ZAxis depths off its layers. Perhaps
Don is doing something like this? Or perhaps he will tell
you how he gets his displays to work the way you want yours
to.

One other suggestion is to experiment with the order of the
addReference() calls for your different data.

Good luck,
Bill

On Sat, 31 Jan 2004, Kevin Manross wrote:

>
> Greetings,
>
> I'm still struggling with the use of Alpha in a 2D display
> (TwoDDisplayRendererJ3D to be specific).  I have a FlatField
> (lat,lon)->Alt in a 2D display.  I then create a "wedge" shape using
> DelaunayCustom.fill and add the shape to the display while setting its
> alpha value to 0.5.
>
>       ConstantMap[] pointMap = { new ConstantMap (0.0f, Display.Red),
>                                 new ConstantMap (0.0f, Display.Green),
>                                 new ConstantMap (0.0f, Display.Blue),
>                                 new ConstantMap (0.5f, Display.Alpha),
>                                 new ConstantMap (4.0f, Display.PointSize) };
>
>
>      DataReferenceImpl widthRef = new DataReferenceImpl("widthRef");
>      display.addReference(widthRef, pointMap);
>      widthRef.setData(widthSet);
>
> The wedge is not transparent to the displayed data "below" it.  Please see:
>
> http://www.cimms.ou.edu/~kmanross/VCPRPE/VisADSamples/VisADAlphaIssue.gif
>
>
> The only thing that changing the value for Display.Alpha does it change
> the color of the wedge from black (0.0) to white (1.0).
>
> I am hoping for the wedge to behave like the transparent radar echoes do
>   in Don Murray's 1st two examples:
>
> http://www.unidata.ucar.edu/staff/donm/radar_pics.html
>
> where you can see the state boundaries below the radar echo.
>
> Also, If I translate the displayed image (left click drag) to the upper
> left corner, it covers up the cursor readout when the middle button is
> clicked.  Is there a way that I can ensure that readout remains visible
> when data is displayed in that region of the window?
>
> Many thanks!!
>
> -kevin.
>
>
>
> --
> +------------------------------------------------------------+
> Kevin L. Manross      [KD5MYD] <><           (405)-366-0557
> CIMMS Research Associate               kevin.manross@xxxxxxxx
> [NSSL-WRDD/SWATN]         http://www.cimms.ou.edu/~kmanross
>
> "My opinions are my own and not representative of CIMMS, NSSL,
>   NOAA or any affiliates"
> +------------------------------------------------------------+
>
>