Re: VisAD and transparency

• To: Bill Hibbard <billh@xxxxxxxxxxxxx>
• Subject: Re: VisAD and transparency
• From: Don Murray <dmurray@xxxxxxxxxxxxxxxx>
• Date: Thu, 21 Apr 2005 06:15:58 -0600

Hi Bill-

Bill Hibbard wrote:

Sorting transparent polygons is a very hard problem,
especially for complex and unpredictable shapes like
iso-surfaces. And note the sort order must change as
the user interactively rotates in 3-D. In Vis5D we
got around this problem by using screen-door
transparency, but the last time (a long time ago) I
tried it in Java3D it didn't work right.

Maybe it's time to investigate this again.  Any pointers on
how to do this would be appreciated.

I think transparency is over-rated. 3-D images are
ambiguous enough and using transparency just adds to
that ambiguity.

There are times when in 2D images transparency is
important.  For example, if I want to overlay a radar
image on a satellite image, I want to have portions of
the radar image (missing data) be transparent.  I can do
this, but only if the DataReferences are adding in the
correct order.  There are many other cases where it would
be useful to use transparency (fading images in and out like
Tom does in many of his applets) so while I agree that for
things like 3D displays transparency can be ambiguous, in
the 2D displays, it is a very useful feature and currently
a serious problem in VisAD.

Don
*************************************************************
Don Murray                               UCAR Unidata Program
dmurray@xxxxxxxxxxxxxxxx                        P.O. Box 3000
(303) 497-8628                              Boulder, CO 80307
http://www.unidata.ucar.edu/staff/donm
        "Time makes everyone interesting, even YOU!"
*************************************************************

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  • Re: VisAD and transparency
    • From: Bill Hibbard