[Paraview] Face Data on vtkUnstructuredGrids
George Zagaris
george.zagaris at kitware.com
Mon Oct 31 09:23:43 EDT 2011
Hi Andy,
I tried to address your questions below
On Mon, Oct 31, 2011 at 8:58 AM, Parker, Andrew (UK Filton)
<Andrew.Parker2 at baesystems.com> wrote:
> Hi,
>
> Ok so basically I need to build and store the connectivity for the face-cell for the graph, fine I can do that no problems (a mapping of faces to left and right adjacent cells). But what about actually adding a scalar for each cell (a face of M) to the new mesh F(M)? Can I do that, can that scalar then be visualized?
>
First, the reason for extracting F(M) is that we don't have FaceData
and so, we need to work with PointData and CellData. Since F(M) stores
faces as cells, you can add scalars by just adding cell data to F(M).
This in effect will give you face data on M and you will be able to
visualize it in ParaView.
> Reason for scalar: Basically I have a very large unstructured mesh, and in the solver a flag is used, this scalar that I want to view, has a value on each face. I wish to see that in the mesh and how it change to understand the behavior of the solver, hence I want to see each face value, no interpolation, just the value in the solver, on the face of the mesh.
>
> Assuming the answer is yes to the above, another question I have is, what structure to I hand back to paraview? The input will be M, in the form of a vtkUnstructuredGrid, I still want to see that data on M, but I need to return F(M), a new mesh, looking identical, but having data on its cells (the faces of M) so that I can look at this single lowly scalar. How do I do this?
You could open both files. It is going to require more memory of
course, but, it is not much different from storing the face data
internally.
Is this not a massive waste of memory? I need to build additional
connectivity information for M, which is probably already there inside
paraview I assume, I can't believe it can't map faces to adjacent
cells, plus store a new mesh F(M), just so I can see the data on the
faces....? Why did face normals get a special treatment, and for all
other face data this has been totally missed?
Take a look at http://www.vtk.org/doc/nightly/html/classvtkUnstructuredGrid.html
-- There are some methods that you can use in your implementation.
Again the reason that we need to do that is that ParaView/VTK
currently works with PointData and CellData.
I hope this helps. Let me know if you have any other questions. I'd be
glad to help more with this.
Best,
George
>
> -----Original Message-----
> From: paraview-bounces at paraview.org [mailto:paraview-bounces at paraview.org] On Behalf Of George Zagaris
> Sent: 31 October 2011 12:35
> To: Parker, Andrew (UK Filton)
> Cc: paraview at paraview.org
> Subject: Re: [Paraview] Face Data on vtkUnstructuredGrids
>
>
> *** WARNING ***
>
> This message has originated outside your organisation,
> either from an external partner or the Global Internet.
> Keep this in mind if you answer this message.
>
>
> Hi Andy,
>
> Given your unstructured volume mesh, M, one way to achieve what you describe is the following:
>
> (1) Construct a vtkUnstructureGrid instance, F(M), consisting of the faces of M, i.e., each cell in F(M) is a facet in M.
> (2) Build auxiliary arrays for each cell in F(M) to store which cells in M the face is adjacent to.
>
> I think you can do this in one loop and it should be sufficient for the operations you want to perform, e.g., interpolate to the face etc.
>
> Let me know if you need more help to get started on this.
>
> Best,
> George
>
>
>> Message: 2
>> Date: Mon, 31 Oct 2011 11:32:09 -0000
>> From: "Parker, Andrew (UK Filton)" <Andrew.Parker2 at baesystems.com>
>> Subject: Re: [Paraview] Face Data on vtkUnstructuredGrids
>> To: <paraview at paraview.org>
>> Message-ID:
>> <FC17C27D1141BF4C945453BACB1CB1D10F7DC5 at GLKMS2100.GREENLNK.NET>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Hi,
>>
>>
>>
>> I have to be honest so far there has been no solution/suggestions to the problem I posed. I am particularly interested in the access pattern I described, but also the ability to be able to add a scale to faces of a 3d unstructured mesh, which I can then cut.
>>
>>
>>
>> Any help would be great, I should imagine this is of interest to a lot of people.
>>
>>
>>
>> Andy
>>
>>
>>
>> From: p.p pyloth [mailto:lalujesus at yahoo.co.in]
>> Sent: 29 October 2011 12:16
>> To: Parker, Andrew (UK Filton)
>> Subject: Re: [Paraview] Face Data on vtkUnstructuredGrids
>>
>>
>>
>> *** WARNING ***
>>
>> This message has originated outside your organisation,
>> either from an external partner or the Global Internet.
>> Keep this in mind if you answer this message.
>>
>> I have the same problem
>> I dont know how to export data on surfaces like wall faces through vtk
>> , as vtk is a bulk reader
>>
>> Suppose I want to show data on wall zones,inlet zones,outlet , no idea how to show that.
>> IF you solved ur problem please post the solution
>>
>>
>>
>> --- On Fri, 28/10/11, Parker, Andrew (UK Filton) <Andrew.Parker2 at baesystems.com> wrote:
>>
>>
>> From: Parker, Andrew (UK Filton) <Andrew.Parker2 at baesystems.com>
>> Subject: [Paraview] Face Data on vtkUnstructuredGrids
>> To: paraview at paraview.org
>> Date: Friday, 28 October, 2011, 6:31 PM
>>
>> Hi,
>>
>>
>>
>> I already have an established reader that reads in our bespoke format and converts it to a vtkUnstructuredGrids so that I can view it in Paraview. Furthermore a filter then reads in a solution file in a bespoke format and shows the cell data from the CFD solution. This works great, happy days. However, I now need to show data on the faces on the vtkUnstructuredGrid, a metric. I have two problems, no idea how to set this given the above setup, and two, to compute the metric I could do with the following type of access:
>>
>>
>>
>> Loop over all faces of vtkUnstructuredGrid
>>
>>
>>
>> Get the face centre
>>
>> Get the Left cell centre
>>
>> Get the Right cell centre
>>
>>
>>
>> Do some stuff?..
>>
>>
>>
>> Set a scale on the face to be a number based on the
>> stuff
>>
>>
>>
>> Finish
>>
>>
>>
>> I have no idea how to access the vtkUnstructuredGrid in the above to pattern???
>>
>>
>> Can anybody help, it would be very useful? examples more than welcome.
>>
>>
>> Cheers,
>>
>> Andy
>>
>>
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