object render order

[Tim Hutton]

As I understand it, transparency is not properly implemented in OpenGL, I
too have seen odd behaviours. I don't know how to get round this, or
whether it is generally regarded as a bug.

At 13:31 14/09/99 -0500, Bryan VanDeVen wrote:
>
>I seem to be having some troubles with object order.  I have an
>application that displays an isosurface of sonar signal excess along
>with the underlying bathymetry (a warped grid).   At certain view
>angles, the surface can be seen (correctly) above the basin actor.
>However, when a user starts interacting, things run afoul.  Some of the
>polygons that make up the warped grid basin begin to "pop up front" in
>front of the isosurface as the scene is rotated.  In fact starting from
>a view straight down with all of the basin correctly behind the
>isosurface, just zooming straight out will produce this behaviour where
>the basin starts to appear "above" the isosurface.
>
>I'm willing to believe that perhaps the basin and the surface aren't as
>precisely lined up as could be, but it seems to me scenes should still
>render consistently (right or wrong) through rotations and zooming,
>maintaining initial relative positions even if they are off.
>
>This happens whether the basin is opaque or semi-transparent, stripping
>or decimating the grid does not seem to give any change, and the order
>in which I add the actors does not seem to matter either.
>
>Someone please tell me I am overlooking something simple and stupid :)
>Any and all advice is very welcome.
>
>TIA,
>
>--
>Bryan Van de Ven
>Applied Research Labs
>University of Texas, Austin
>
>
>
>-----------------------------------------------------------------------------
>This is the private VTK discussion list.  Please keep messages on-topic.
>Check the FAQ at: <http://www.automatrix.com/cgi-bin/vtkfaq>
>To UNSUBSCRIBE, send message body containing "unsubscribe vtkusers" to
><majordomo at gsao.med.ge.com>.  For help, send message body containing
>"info vtkusers" to the same address.     Live long and prosper.
>-----------------------------------------------------------------------------
>
>
>
---------------------------------------------------------------------------
Tim Hutton, Research Assistant            Email: T.Hutton at eastman.ucl.ac.uk
MINORI Project                     http://www.eastman.ucl.ac.uk/~dmi/MINORI
Dental and Medical Informatics                   Tel: [+44] (0171) 915 2344
Eastman Dental Institute, UCL                    Fax: [+44] (0171) 915 2303
256 Gray's Inn Road, London WC1X 8LD, UK
---------------------------------------------------------------------------
This email represents the views of the sender alone and must not be
construed as representing the views of the Eastman Dental Institute. It may
contain confidential information and may be protected by law as a legally
privileged document and copyright work. Its content should not be disclosed
and it should not be given or copied to anyone other than the person(s)
named or referenced above. If you have received this email in error, please
contact the sender.



-----------------------------------------------------------------------------
This is the private VTK discussion list.  Please keep messages on-topic.
Check the FAQ at: <http://www.automatrix.com/cgi-bin/vtkfaq>
To UNSUBSCRIBE, send message body containing "unsubscribe vtkusers" to
<majordomo at gsao.med.ge.com>.  For help, send message body containing
"info vtkusers" to the same address.     Live long and prosper.
-----------------------------------------------------------------------------