Using the dataset below I can reproduce the issue on my workstation using 4 processes and both hardware and mesa rendering.

burlen wrote:
Ken,

Here is a dataset that I am able to reproduce with:
http://nashi-submaster.ucsd.edu/movies/PV/holes.tar.gz

run with 96 procs. Set the view to +y. If the long holes aren't appearing in your view I found that smaller holes can show up by rotating the plane in small increments about either the x or z axis. These ones are pretty small so you have to look closely.

Burlen

Moreland, Kenneth wrote:
Burlen,

Is there any possible way you can send me some data or replicate the problem with something like the Mandelbrot source? So far I have not been able to replicate it exactly.

-Ken


On 1/5/10 2:34 PM, "burlen" <[email protected]> wrote:

    Ken,
Some bad news, this patch didn't solve the problem, the holes returned
    on my first run.
    Burlen


    Moreland, Kenneth wrote:
> That was not intended to be a solution, but rather a diagnostic. My
    > guess is that there are precision errors in the rasterization
    when the
> viewport is shifted. Could you restore vtkIceTRenderManager and try
    > the attached patch to IceT?
    >
    > -Ken
    >
    >
    > On 12/10/09 12:26 PM, "burlen" <[email protected]> wrote:
    >
    > Hi Ken,
    >
    > it seems to have solved the problems. I say that with fingers
    > crossed, I
    > haven't seen holes any since your suggested changes, where before
    > I was
    > seeing them quite often, popping up from time to time.
    >
    > Burlen
    >
    > Moreland, Kenneth wrote:
    > > Hmm. It is possible that the “floating viewport” feature of IceT
    > could
    > > be causing troubles with precision. Could you try adding
    > >
    > > icetDisable(ICET_FLOATING_VIEWPORT);
    > >
    > >
    > > somewhere in the vtkIceTRenderManager::UpdateIceTContext()
    method and
    > > see if the problem goes away?
    > >
    > > -Ken
    > >
    > >
    > > On 12/7/09 10:11 AM, "burlen" <[email protected]> wrote:
    > >
    > > Hi Ken,
    > > For that figure you mention I turned on "surface with edges" to
    > > show the
> > cell size better. Sorry I can see how that could be confusing. But
    > > just
    > > to clarify, there aren't actually any holes in the surface.
    > >
    > > Here is another zoom in of the same area where "surface with
    > edges" is
    > > off and you can see that there are no holes.
    > > http://nashi-submaster.ucsd.edu/movies/PV/bug-zoom.png
    > >
> > Now I also have hit a case where after running through D3 I got a
    > hole
    > > at the process boundary. this run had 80 processes, the surface
    shown
    > > has dimensions of 5.5 x 10 units with 1500 x 2727quads with side
    > > 0.0036
    > > units.
    > > http://nashi-submaster.ucsd.edu/movies/PV/bug-d3.png
    > >
    > > I am only seeing this with the small quads and in parallel at
    process
    > > boundaries.
    > >
    > > Burlen
    > >
    > >
    > > Moreland, Kenneth wrote:
    > > > Burlen,
    > > >
    > > > For the zoom in, you say there are no holes/lines, but in the
    > image I
    > > > see a grid of lines. It looks like you have a bunch of little
    quads
> > > with spacing in between them. Is this the case? If so, then the
    > > “hole”
> > > artifacts you see on the bottom of the screen are probably simply
    > > > aliasing artifacts. They are places where the pixel happens to
    > align
    > > > right where the gap is.
    > > >
    > > > I can’t think of an easy way around this (other than to
    modify your
    > > > data to remove the gaps, if that makes sense). Anti-aliasing
    > > > techniques such as oversampling or smoothing would probably
    fix the
    > > > problem, but they would also break the parallel rendering so
    > they are
    > > > no good.
    > > >
    > > > -Ken
    > > >
    > > >
    > > > On 12/5/09 12:18 AM, "burlen" <[email protected]> wrote:
    > > >
    > > > its ugly but I get a lot better performance by splitting the
    > work up
    > > > dynamically with a small grain size. in the run shown below
    > there are
    > > > only 16 processes but there are a whole lot of process
    boundaries.
    > > >
    > > > I was able to reproduce it on a second system today.
    > > >
> > > these holes are pretty non-deterministic in where they show up.
    > > moving
    > > > the camera they can show up in different places. Which makes
    > sense if
> > > this is related to some parallel rendering/finite precision issue
    > > with
    > > > all those process boundaries. The small size of the quads are
    > also a
> > > factor, because I didn't ever notice it before when using larger
    > > > quads.
    > > >
    > > > I saved the data as a legacy file and opening it on my desktop
    > > > there are
> > > no issues, so its definitely a parallel only issue. Also running
    > > > through
    > > > D3 seems to fix it, but the issue may still be there because
    > with the
    > > > minimal number of process boundaries its much less likely to
    > get the
    > > > camera in just the right position.
    > > >
    > > > Berk Geveci wrote:
    > > > > Ouch. That's very distributed :-) Does the problem go away
    > when you
    > > > > decrease the number of partitions?
    > > > >
    > > > > On Thu, Dec 3, 2009 at 10:55 AM, burlen
    <[email protected]>
    > > > wrote:
    > > > >
> > > >> I'm seeing lines where the background shows through a surface
    > > > polydata of
    > > > >> quads. When I zoom into the region to investigate the
    holes are
    > > > gone. Moving
    > > > >> the image around the holes appear in different places. They
    > > > depend on camera
> > > >> position. In this surface there are 2.5E6 quads. the area is
    > > > 10x16 units and
    > > > >> the number of quads is 1250x2000. each quad has 0.008
    units on a
    > > > side. I
> > > >> hadn't seen the holes before going to this higher resolution.
    > > > It's likely
    > > > >> that the hole is near a process boundary, in my polydata
    filter
    > > > each process
    > > > >> adds his quads to his output polydata, in this run the
    quads are
    > > > distributed
    > > > >> in strips of 512 as needed.
    > > > >>
    > > > >> 3 holes/lines in bottom half of the image (black background
    > > > shows through):
    > > > >> http://nashi-submaster.ucsd.edu/movies/PV/bug.png
    > > > >>
    > > > >> zoom in no holes/lines:
    > > > >> http://nashi-submaster.ucsd.edu/movies/PV/bug-zoom-2.png
    > > > >>
    > > > >> process boundaries (from process id filter):
    > > > >> http://nashi-submaster.ucsd.edu/movies/PV/bug-procs.png
    > > > >>
> > > >> Should PV be able to handle a polydata distributed like this?
    > > > >>
    > > > >>
    > > > >>
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    > > > **** Kenneth Moreland
    > > > *** Sandia National Laboratories
    > > > ***********
    > > > *** *** *** email: [email protected]
    > > > ** *** ** phone: (505) 844-8919
    > > > *** web: http://www.cs.unm.edu/~kmorel
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    > > >
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    > >
    > >
    > >
    > >
    > > **** Kenneth Moreland
    > > *** Sandia National Laboratories
    > > ***********
    > > *** *** *** email: [email protected]
    > > ** *** ** phone: (505) 844-8919
    > > *** web: http://www.cs.unm.edu/~kmorel
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> <http://www.cs.unm.edu/%7Ekmorel> <http://www.cs.unm.edu/%7Ekmorel>
    > >
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    >
    >
    >
    > **** Kenneth Moreland
    > *** Sandia National Laboratories
    > ***********
    > *** *** *** email: [email protected]
    > ** *** ** 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: [email protected]
** *** ** phone: (505) 844-8919
*** web: http://www.cs.unm.edu/~kmorel <http://www.cs.unm.edu/%7Ekmorel>



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