Re: VisAD and transparency

• To: JR Schmidt <schmidt@xxxxxxxxxxxxx>
• Subject: Re: VisAD and transparency
• From: Bill Hibbard <billh@xxxxxxxxxxxxx>
• Date: Thu, 21 Apr 2005 03:39:51 -0500 (CDT)

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.

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

Cheers,
Bill

On Wed, 20 Apr 2005, JR Schmidt wrote:

> I have encountered a problem with VisAD and isosurface transparency.  From
> browsing the archives of the list, it seems that there may be a problem with
> transparency in general, due to a lack of a z-sort in Java3D.  I am not sure
> whether this issue has been resolved in Java3D 1.3.
>
> Transparency seems to work, for the most part, except that I get 'banding'
> in the resulting image.  The banding changes as I rotate the image.  For
> example, see
> http://www.webmo.net/test/moviewer.jpg
>
> Are such problems to be expected, due to deficiencies in Java3D?  Or are
> there possible workarounds?  I have tried changing the transparency mode in
> the GraphicsControl, which does not seem to help (or hurt).
>
>     JR Schmidt
>     UW-Madison
>
>

• Follow-Ups:
  • Re: VisAD and transparency
    • From: Don Murray

• References:
  • VisAD and transparency
    • From: JR Schmidt