Adding the manifold ID to a DataOutFaces<dim>

[Bruno Blais]

Dear all, 

I hope you are well.

I am currently working extensively with adaptive mesh refinement and I feel the need to output the 2D boundary surface of my 3D mesh (thus a dim=2, spacedim=3 type of problem)

I have realized there is an amazing Data out object that exists  DataOutFaces<dim> which does exactly what I need.

I have figured out how to attach data to it and how to write parallel vtu files with it. However, I would like to add a data to this DataOutFace that would give out the manifold number (or the boundary id) of my boundary condition. However, since this DataOutFace only contains face of the surface, I am really unsure how to iterate on this structure.
I saw that there is a first_face() and next_face() function that should allow me to iterate over the face. However, this structure appears to be an std::pair and from this point I am confused as to how to use it.

Could somebody point me in the right direction? I have looked online, but it seems this class is not used extensively.

Thank you very much for your help,

Bruno

[Jean-Paul Pelteret]

Hi Bruno,

I haven’t used this class before, and admittedly haven’t gone digging too deep for examples of where its used. But here are a few examples (one tutorial and a couple from the test suite) that may be able to guide you in the right direction. At first glance, its seems to work more-or-less like the normal DataOut class.

https://www.dealii.org/developer/doxygen/deal.II/step_51.html

https://github.com/dealii/dealii/blob/master/tests/data_out/data_out_faces_01.cc

https://github.com/dealii/dealii/blob/master/tests/data_out/data_out_faces_postprocessor_scalar_02.cc

I hope that this helps you a little.

Best,

Jean-Paul

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[Jean-Paul Pelteret]

Sorry, I hit send too soon. It might be possible to use a PostProcessorScalar to extract the manifold ID from the cell that the post-processor is actively working on, and return that value as the outputted “computed_quantities". Then you don’t need to worry about any of the iterating yourself. But I’m not quite sure if you can get it to colour each face as a single manifold ID (as it might interpolate the values between adjacent faces). That said, I would be surprised if this were not somehow possible to do, since we allow the cell material ID to be output as a cell constant value.

Maybe someone else on the mailing list knows more about this class, and could provide more hints?

[Wolfgang Bangerth]

On 4/9/20 5:00 PM, Jean-Paul Pelteret wrote:
> Sorry, I hit send too soon. It might be possible to use a PostProcessorScalar
> to extract the manifold ID from the cell that the post-processor is actively
> working on, and return that value as the outputted “computed_quantities". Then
> you don’t need to worry about any of the iterating yourself.

Yes, that's the way I would have used.

> But I’m not quite
> sure if you can get it to colour each face as a single manifold ID (as it
> might interpolate the values between adjacent faces). That said, I would be
> surprised if this were not somehow possible to do, since we allow the cell
> material ID to be output as a cell constant value.

For DataOutFaces, you get a different data record for each face. So you should
definitely be able to plot individual faces of the same cell with different
colors.

Best
W.

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Wolfgang Bangerth email: bang...@colostate.edu
www: http://www.math.colostate.edu/~bangerth/