[vtk-developers] VTK and transparency problems

[Wylie, Brian]

Actually the Sandia folks were just talking about this today. :)

I'm assuming the cull face trick will avoid a z-sort of the polygons for
cylindrical, spherical, tubular geometries by making sure that back
faces (which tend to be 'farther' back in the scene) get rendered first
and then front faces (which tend to be 'closer' get rendered over the
back faces). Is that the jist? 

Also I second putting this into VTK as default, or at least into
ParaView 2.4. :)

  Brian Wylie - Org 9227
  Sandia National Laboratories
  MS 0822 - Building 880/A1-J
  (505)844-2238 FAX(505)845-0833                       
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                                    Unleash the Beast
 

> -----Original Message-----
> From: vtk-developers-bounces+bnwylie=sandia.gov at vtk.org 
> [mailto:vtk-developers-bounces+bnwylie=sandia.gov at vtk.org] On 
> Behalf Of Ken Martin
> Sent: Friday, September 30, 2005 2:22 PM
> To: 'Prabhu Ramachandran'; vtk-developers at vtk.org
> Subject: RE: [vtk-developers] VTK and transparency problems
> 
> > Every so often we encounter users (on vtkusers and 
> elsewhere) who run 
> > into difficulties with VTK and transparent actors.  VTK 
> does so many 
> > things out-of-the-box and does them so well that they are usually 
> > quite surprised that something that *they* think ought to 
> be a simple 
> > issue does not work correctly at all.
> > 
> > I am no expert but do understand that this is not a trivial 
> thing to 
> > solve especially when performance is concerned.  However, 
> this issue 
> > comes up very often and the requirement is not entirely 
> unreasonable 
> > either.
> > 
> > I noticed that Clinton Stimpson had this response:
> > 
> >  
> http://public.kitware.com/pipermail/vtkusers/2005-January/077971.html
> > 
> > It appears from his comments that this approach works 90% 
> (?) of the 
> > time.  So would it be possible to make this the default behavior as 
> > part of VTK?  Or is there a better way than this?  Comments?
> 
> The approach he describes would certainly improve the quality 
> of transparent renderings at a cost of rendering the 
> transparent actors twice. His approach is a very good 
> compromise between performance and correct renderings.
> Someone should add this to VTK in my opinion.
> 
> Thanks
> Ken
> 
> 
> 
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