[Paraview] tube filter, surfaces aren't closed?

[burlen]

Hi Ken,

You are correct. when VTK creates an OSMesa context is requests the 
default. OSMesa's default depth buffer is 16 bits, and that is the 
source of the problem. Explicitly requesting a 32 bit depth buffer 
solves the problems with the artifacts and the compositing. See the 
attached patch. Thanks to tom fogal for suggesting this during our 
conversation on the mesa-users mail list.

ParaView should probably default to a 32 bit depth buffer. I have just 
sent this to the vtk-dev list as well, since it looks like more of a VTK 
issue.

Burlen


Moreland, Kenneth wrote:
> I’m guessing that this is a z-buffer precision issue. The nVidia card 
> must be using a higher precision z-buffer or doing something else that 
> is preventing the z-fighting that appears to be happening in the Mesa 
> implementation.
>
> -Ken
>
>
> On 1/18/10 11:47 AM, "burlen" <burlen.loring at gmail.com> wrote:
>
>     Yes, that is the case. There are 200 lines , each a single cell , and
>     the pvtp reader splits them up fairly evenly amongst processes to
>     begin
>     with. D3 is moving stuff around but it doesn't noticeably change
>     the result.
>
>     Moreland, Kenneth wrote:
>     > Looking at the mesa-artifacts-decomp.png image, it appears that you
>     > have many tubes that are coincident (or at least close to
>     coincident).
>     > There might be z-buffer resolution problems. What happens if you run
>     > the geometry through D3?
>     >
>     > -Ken
>     >
>     >
>     > On 1/15/10 10:28 AM, "burlen" <burlen.loring at gmail.com> wrote:
>     >
>     > FYI, I re-organized the images illustrating the bug, and made a
>     > comparison of nvidia to mesa rendering on two cases 1) the
>     > artifacts 2)
>     > the parallel inconsistency, and removed the older images.
>     >
>     > 1)
>     > http://nashi-submaster.ucsd.edu/movies/PV/tube-filter-artifact/mesa-artifacts.png
>     > http://nashi-submaster.ucsd.edu/movies/PV/tube-filter-artifact/nvidia-no-artifacts-decomp.png
>     >
>     > 2)
>     > http://nashi-submaster.ucsd.edu/movies/PV/tube-filter-artifact/mesa-artifacts-decomp.png
>     > http://nashi-submaster.ucsd.edu/movies/PV/tube-filter-artifact/nvidia-no-artifacts.png
>     >
>     > burlen wrote:
>     > > So you are right these are artifacts not holes. Nasty looking
>     ones at
>     > > that. zooming in enough makes the artifacts receded toward the
>     egdes
>     > > of the tube. After some experimentation I'm finding that this has
>     > > something to do with mesa. It is reproducible only when using mesa.
>     > > Hardware rendering works fine, no artifacts.
>     > >
>     > > There also looks to be two things going on, 1) the artifacts, 2)
>     > > inconsistent selection of the visible faces on parallel runs.
>     > This is
>     > > shown here:
>     > >
>     http://nashi-submaster.ucsd.edu/movies/PV/tube-filter-artifact/decomp-8-procs.png
>     > >
>     > >
>     > > I was using PV on this cluster fine back in dec to make very
>     similar
>     > > figures with stream tubes and didn't see any of these issues...
>     > >
>     > > I added the dataset to reproduce to the bug report.
>     > >
>     > > Moreland, Kenneth wrote:
>     > >> It could be a rendering artifact. What happens when you zoom into
>     > >> the problem area?
>     > >>
>     > >> -Ken
>     > >>
>     > >>
>     > >> On 1/14/10 12:24 AM, "burlen" <burlen.loring at gmail.com> wrote:
>     > >>
>     > >> Any ideas as to why tubes from the tube filter aren't closed
>     > >> surfaces
>     > >> now? screenshot:
>     > >> http://public.kitware.com/Bug/view.php?id=10139
>     > >>
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>     > >>
>     > >> **** Kenneth Moreland
>     > >> *** Sandia National Laboratories
>     > >> *********** *** *** *** email: kmorel at sandia.gov
>     > >> ** *** ** phone: (505) 844-8919
>     > >> *** web: http://www.cs.unm.edu/~kmorel
>     <http://www.cs.unm.edu/%7Ekmorel>
>     > <http://www.cs.unm.edu/%7Ekmorel>
>     > >> <http://www.cs.unm.edu/%7Ekmorel>
>     > >>
>     > >
>     >
>     >
>     >
>     >
>     >
>     > **** Kenneth Moreland
>     > *** Sandia National Laboratories
>     > ***********
>     > *** *** *** email: kmorel at sandia.gov
>     > ** *** ** phone: (505) 844-8919
>     > *** web: http://www.cs.unm.edu/~kmorel
>     <http://www.cs.unm.edu/%7Ekmorel>
>     > <http://www.cs.unm.edu/%7Ekmorel>
>     >
>
>
>
>
>
> **** Kenneth Moreland
> *** Sandia National Laboratories
> ***********
> *** *** *** email: kmorel at sandia.gov
> ** *** ** phone: (505) 844-8919
> *** web: http://www.cs.unm.edu/~kmorel <http://www.cs.unm.edu/%7Ekmorel>
>

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