[Paraview] Question about Integrate Variables Filter

[Yuanxin Liu]

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.
>
>
> Magician
>
>
> On 2012/06/08, at 12:54, Magician wrote:
>
> > Hi all,
> >
> >
> > I'm now comparing integration 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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