[Paraview] dataset questions

[SamuelKey]

John Doe,

*.pvd file is documented in the PV user's manual. Currently, the *.pvd 
file can only reference the VTK XML-formatted files. I have seen 
comments that in the future the *.pvd files will be able to reference 
some other formats.

Each file must be an independent *displayable* graphics object. An 
XML-formatted file has a point data set (coordinates). Each geometric 
entity (point, line, triangle, quadrilateral, hexahedron, et cetera is 
an integer n-tuple that references (with offsets) points that make up 
its vertexes.

All 1-D lines can be described in one set; all triangles can be 
described in another set. I am not sure that you can have different data 
on lines and triangles without using zero fill on the other geometric 
entities.

If the images you want to display consider all triangles alike and all 
lines alike, and it is important to have different data on lines and 
triangles use two files. Both files will have the same points repeated 
but PV does not care. Read in the files one after another and 
graphically process them independently.

Unless you are very familiar with "filters" and "pipe lines," and PV's 
ability to manage them it is almost impossible to describe how they work 
with words alone.

I recommend you create two toy data files, one for lines and one for 
triangles. Read them in independently and learn by trial-and-error how 
PV works. The more you use PV, the smarter it gets.



John Doe wrote:
> Looking in the vtk file formats document, I can see that the xml
> format allows multiple pieces in the same unstructured mesh.  This
> should suit my purposes.
> 
> I am assuming I can have two pieces per region.  One piece would be
> for point and line data.  The other piece would be for triangle data.
> I assume it would be ok for the two region to share the same
> coordinates?
> 
> Thanks,
> 
> Juan
> 
> On Thu, Jun 5, 2008 at 3:23 PM, John Doe <ufnoise at gmail.com> wrote:
>> Hi Sam,
>>
>> Thanks for the excellent ideas.
>>
>> Since:
>> 1 I have on average 2 triangles for every line.
>>
>> 2. And having zero data for the triangles interspersed with nonzero
>> data for the lines may not work out so well.
>>
>> Perhaps I can have a vtk file for lines and a vtk file for triangles?
>>
>> I can only find documentation online for the vtk format.  Is there
>> documentation for the pvd format?  The example file I saw online is
>> xml like, I guess this implies that I'd have to use xml for the
>> individual data files?
>>
>> Thanks,
>>
>> Juan
>>
>>
>>
>> On Thu, Jun 5, 2008 at 1:57 PM, SamuelKey <samuelkey at comcast.net> wrote:
>>> Juan,
>>>
>>> For what it is worth here is my 2 centavos,
>>>
>>> First, I would consider the VTK XML data format.
>>>
>>> Second, I have found that it works really well to consider each *.vt* file
>>> as an independently displayable graphics object. One then uses a *.pvd
>>> meta-file (an ASCII "mother" file) to get PV to read them all at once.
>>>
>>> Parallel generated data sets are managed this way. I use this approach to
>>> generate separate objects based on material type. PV does not care (or know)
>>> that they were not generated in parallel. As independently displayable
>>> graphics objects, they need to have their own point sets. PV doesn't worry
>>> about one or more points having "matching" locations.
>>>
>>> Each object has its own set of iso-surfaces so that on boundaries the data
>>> from each side is used and you get disconnected iso-surfaces which in my
>>> case is exactly what I want.
>>>
>>> The question of different fields/data on different objects someone else will
>>> need to answer. (You can always flesh out zero's.)
>>>
>>> Sam Key
>>>
>>> John Doe wrote:
>>>> I was going to use implement a vtk writer for my program.  I would
>>>> like to use the vtk ascii datafile format.  A few questions:
>>>>
>>>> 1. I have multiple regions.  Some of these regions share coordinates
>>>> at an interface.  Do I have to average the data on both sides of the
>>>> interface, or is there a way to put 2 values at the same point?  Will
>>>> paraview complain about duplicate coordinates (collinear points)?
>>>>
>>>> 2. Some data fields only exist in certain regions.  Does that mean I
>>>> have to set 0 values in the regions the field does not exist?
>>>>
>>>> 3. I have points, lines, and triangles.  If I put data on lines, does
>>>> that mean I have to define the same data fields on all of the other
>>>> cell types in my design as well?  For example, I have current flowing
>>>> along lines, but not through triangles.  So it wouldn't make sense to
>>>> have current data defined for the triangles.
>>>>
>>>> Thanks,
>>>>
>>>> Juan
>>>> _______________________________________________
>>>> ParaView mailing list
>>>> ParaView at paraview.org
>>>> http://www.paraview.org/mailman/listinfo/paraview
>>>>
> 
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