[Paraview] Question about Integrate Variables Filter

[Yuanxin Liu]

Hi, Sam,
  I am still having trouble with the file. I tried to open it with several
programs on windows   and linux platforms and could not open it.  If you
have a .tex file, maybe you can try to post that instead.
thanks,
Leo

On Sun, Jun 10, 2012 at 8:49 PM, Samuel Key <samuelkey at bresnan.net> wrote:

>  Leo,
>
> Here is the *.pdf file again.
>
> Sam
>
>
> On 6/10/2012 6:36 PM, Yuanxin Liu wrote:
>
> Hi, Sam,
>   Would you mind reposting this?  The pdf file seems corrupt.
> thanks,
> Leo
>
> On Sun, Jun 10, 2012 at 7:38 PM, Samuel Key <samuelkey at bresnan.net> wrote:
>
>>  Hi Leo,
>>
>> Though likely more arithmetically intense than you would like, I have
>> attached a 3-page write-up on how to do an exact integration over the
>> surface of a bi-linear isoparametric coordinate based quadrilateral in
>> three-space. It is easily adapted to a flux integration as well.
>>
>> If it helps, please free to incorporate it into ParaView.
>>
>> Sam Key.
>>
>>
>>
>>
>> On 6/10/2012 12:55 PM, Yuanxin Liu wrote:
>>
>> Hi,
>>    This is not really a bug, but just what the linear precision
>> integration does.  As you can see in vtkIntegrateAttributes.cxx:215, the
>> quad cell is basically cut into two triangles along a diagonal, integration
>> is done for each triangle and the results are added up.   So, depending
>> where your "1" falls on a diagonal vertex, you will get different results.
>>
>>  Leo
>>
>>
>> On Sat, Jun 9, 2012 at 8:57 AM, Magician <f_magician at mac.com> wrote:
>>
>>> Hi all,
>>>
>>>
>>> Now I found a bug of the filter.
>>>
>>> My ParaView's version is 3.14.1.
>>> I define node names as below:
>>> > c--d
>>> > |  |
>>> > a--b
>>>
>>> Case 1: a=1.0, b=0.0, c=0.0, d=0.0
>>> Integration Value = 0.33333
>>>
>>> Case 2: a=0.0, b=1.0, c=0.0, d=0.0
>>> Integration Value = 0.16666
>>>
>>> ( Case 3: a=0.0, b=0.0, c=1.0, d=0.0
>>>
>>> Integration Value = 0.16666
>>>
>>> Case 4: a=0.0, b=0.0, c=0.0, d=1.0
>>> Integration Value = 0.33333
>>>
>>> So Integration Values are calculated as (2*a+b+c+2*d)/6.
>>> I think it's not a good result.
>>> ,br>
>>> Magician
>>>
>>>
>>> On(2012/06/08, at 12:54, Magician wrote:
>>>
>>> > Hi all,
>>> >
>>> >
>>> > I'm now comparing integjation results of each postprocessors.
>>>
>>> > I made a simple Quadratic VTK model as below:
>>> >> # vtk DataFile Version 2.0
>>> ( >
>>>
>>> >> QuadCell
>>> >> ASCII
>>> >> DATASET UNSTRUCTURED_GRID
>>> >> POINTS 4 FLOAT
>>> >> 0 0 0
>>> >> 1 0 0
>>> >> 0 1 0
>>> >> 1 1 0
>>> >> CELLS 1 5
>>> >> 4 0 1 3 2
>>> >> CELL_TYPES 1
>>> >> 9
>>> >> POINT_DATA 4
>>> >> SCALARS scalar FLOAT 1
>>> >> LOOKUP_TABLE DEFAULT
>>> >> 0.0
>>> >> 1.0
>>> >> 2.0
>>> >> 4.0
>>> >
>>> > When I apply Point Data to Cell Data filter,
>>> > scalar values are interpolated as 1.75.
>>> > It may be calculated as (0.0+1.0+2.0+4.0)/4.0.
>>> >
>>> > But when I apply Integrate Variables filter,
>>> > scalar value is integrated as 1.833....
>>> > The area value of quadratic cell is 1.0, so I thought
>>> > integrated values should be equal to cell data.
>>> >
>>> > How the integrated value is calculated?
>>> >
>>> >
>>> > Magician
>>>
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>>
>>
>>
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