[Paraview] holes in distributed polydata

Moreland, Kenneth kmorel at sandia.gov
Mon Jan 18 13:54:10 EST 2010


I can't find anything wrong other then there must be some sort of precision issue that is interfering with the decision of when to draw a polygon that is smaller than a pixel.  I just checked in a change to IceT that prevents shifting around the projection matrix in single-display mode.  That should fix the problem.

-Ken


On 1/15/10 11:07 AM, "burlen" <burlen.loring at gmail.com> wrote:

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" <burlen.loring at gmail.com> 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" <burlen.loring at gmail.com> 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" <burlen.loring at gmail.com> 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" <burlen.loring at gmail.com> 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
>>     <burlen.loring at gmail.com>
>>     > > > 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: 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>
>> <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>
>> <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>
>>
>





   ****      Kenneth Moreland
    ***      Sandia National Laboratories
***********
*** *** ***  email: kmorel at sandia.gov
**  ***  **  phone: (505) 844-8919
    ***      web:   http://www.cs.unm.edu/~kmorel

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