[vtkusers] Re: Strange VTK Behavior...

[Andrea Gavana]

Hello NG,

    OK, after a day of trying different things, I have a VTK data file in
which only the first 2 vertical "layers" of my unstructured grid are shown.
The new grid is composed by 5014 hexahedron cells (having thus 40112
points), with a single property as scalar. By using the script attached to
the mail, I have checked that there are *NO* coincident cells. The file in
which the coincident cells should be stored comes out empty.
So, now, this is what I have by trying my script, Mayavi and Paraview:

1) My script:  http://xoomer.virgilio.it/infinity77/myscript.JPG
2) Mayavi: http://xoomer.virgilio.it/infinity77/mayavi.jpg
3) Paraview: http://xoomer.virgilio.it/infinity77/paraview.jpg

All of them shows this problematic behavior... the cells seems corrupted
with severe artifacts, even if I have checked that there are no coincident
cells (at this point I hope that my checking script is wrong...). The VTK
data file, for those interested in, is here:

http://xoomer.virgilio.it/infinity77/KPO5.zip

Is about 250 Kb, much smaller than the other :-)

I really hope that I am doing something wrong somewhere... otherwise it
starts to look like a bug, but I am clearly too inexperienced to talk about
bugs.

Thank you very mucg for your help and suggestions.

Andrea.


On 4/4/06, Andrea Gavana <andrea.gavana at gmail.com> wrote:
>
>
> Hello Goodwin & NG,
>
>     thank you very much for your help. Unfortunately, it seems that the
> use of these 2 methods does not make any difference :-( . Anyway, you are
> right, there are quite a lot of duplicated cells... the problem is that the
> grid comes in a binary format from another gridding software (which I can
> not control). Mhm... is there a way in VTK to "hide" or filter out the cells
> that are duplicated (share the same points)? I think this is the last
> alternative I have...
>
> Thank you very much for your help and suggestions.
>
> Andrea.
>
>  On 4/4/06, Goodwin Lawlor <goodwin.lawlor at ucd.ie> wrote:
> >
> > Andrea Gavana wrote:
> > >
> > > Hello John & NG,
> > >
> > >     I made a relatively small example (with a VTK data file) that
> > shows
> > > the problem. Basically, once loaded the VTK file, just zoom since the
> > > grid occupies all the available screen space of the VTK window (more
> > or
> > > less). Then, if you rotate the scene you will see that the grid is
> > > corrupted in some zones (you will see some artifacts). This may be
> > > reproduced using:
> > >
> > > 1) The script I am attaching (sorry it's Python);
> > > 2) Mayavi
> > > 3) Paraview
> > >
> > > At this point I don't know what to do or to think... does anyone have
> > a
> > > suggestion? Could please someone try and see if he/she gets the same
> > > results? The VTK Data file is here:
> > >
> > > http://xoomer.virgilio.it/infinity77/KPO3.zip
> > >
> > > It's 600 Kb zipped and about 5 MB unzipped... sorry for that, but it
> > is
> > > the only grid I have to show that problem...
> > >
> > > Thank you very much for every suggestion/hint.
> > >
> > > Andrea.
> > <SNIP>
> >
> > Hi Andrea,
> >
> > Looks like coincident cells... try:
> >
> > surfaceMapper.SetResolveCoincidentTopologyToPolygonOffset()
> >
> > or
> >
> > surfaceMapper.SetResolveCoincidentTopologyToShiftZBuffer()
> >
> > hth
> >
> > Goodwin
> >
> >
> > _______________________________________________
> > This is the private VTK discussion list.
> > Please keep messages on-topic. Check the FAQ at: http://www.vtk.org/Wiki/VTK_FAQ
> >
> > Follow this link to subscribe/unsubscribe:
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> >
>
>
>
> --
> "Imagination Is The Only Weapon In The War Against Reality."
>
> http://xoomer.virgilio.it/infinity77/
>



--
"Imagination Is The Only Weapon In The War Against Reality."

http://xoomer.virgilio.it/infinity77/
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fid = open("KPO5.vtk", "rt")

cellpoints = []
linecount = 0
singlecell = []

while 1:

    tline = fid.readline()

    if not tline:
        break

    if tline.find("POINTS ") >= 0:

        while 1:

            tline = fid.readline().strip("\n")

            if len(tline.strip()) == 0 or tline.find("CELLS") >= 0:
                break

            singlecell.extend(tline.split(" "))
            linecount = linecount + 1
            
            if linecount%8 == 0:
                cellpoints.append(singlecell)
                singlecell = []
                
        break

fid.close()

fid = open("ResultsVTK.txt", "wt")

count = 0

for cells in cellpoints:
    if cellpoints[count+1:].count(cells) > 0:
        indx = cellpoints[count+1:].index(cells)
        fid.write(str(count) + " " + str(indx+count+1) + "\n")

    count = count + 1
    print "Cell Number: ", count

fid.close()