[Paraview] Extract Point Data | Nearest Neighbor Location

Sun Aug 5 12:31:44 EDT 2018

You could try sampling the unstructured grid with the polydata. But you
might run into issue if the polydata points end up outside if the
unstructured grid.
You could blow a little bit the unstructured grid by scaling it a bit...

On Sat, Aug 4, 2018 at 10:01 AM Fastl, Thomas <thomas.fastl at kcl.ac.uk>
wrote:

> Hey Sebastien,
>
> That's correct, the 'Extract Surface' filter applied to the
> UNSTRUCTURED_GRID (vtk file 1) results in more POINTS compared to the
> POINTS in the POLYDATA (vtk file 2). In addition, the POINTS in POLYDATA
> (vtk file 2) have some rounding error so that the location of
> 'corresponding points' doesn't match exactly.
>
> Maybe you've already suggested the right approach: Is there a way in
> ParaView to extract the nearest neighbor of all the POINTS in POLYDATA (vtk
> file 2) from the UNSTRUCTURED_GRID (vtk file 1)? I could just write a csv
> file of the POINTS in the POLYDATA (vtk file 2) if that'd makes the nearest
> neighbor approach in ParaView more simple? Thanks.
>
> Best, Thomas
>
> ------------------------------
> *From:* Sebastien Jourdain <sebastien.jourdain at kitware.com>
> *Sent:* Friday, August 3, 2018 9:11:54 PM
> *To:* Fastl, Thomas
> *Cc:* paraview
> *Subject:* Re: [Paraview] Extract Point Data | Nearest Neighbor Location
>
> So you are saying that the ExtractSurface on the Unstructured grid won't
> produce the same polydata since it will be more refined than your file2? If
> that's the case, then maybe just looking for point closer could be the
> solution.
>
> On Fri, Aug 3, 2018 at 10:56 AM Fastl, Thomas <thomas.fastl at kcl.ac.uk>
> wrote:
>
> Hey Sebastien,
>
>
> the UNSTRUCTURED_GRID (vtk-file 1) has around 10^8 POINTS, while the
> POYDATA (vtk-file 2) has around 10^6 POINTS, i.e., the POINTS in vtk-file 2
> are a subset of the POINTS in vtk-file 1. Additionally, the POINTS in
> vtk-file 2 have some rounding error so that the location of "corresponding
> points" doesn't matches exactly and a nearest neighbor seems necessary.
>
>
> Best, Thomas
>
> ------------------------------
> *From:* Sebastien Jourdain <sebastien.jourdain at kitware.com>
> *Sent:* Friday, August 3, 2018 17:20
> *To:* Fastl, Thomas
> *Cc:* paraview
> *Subject:* Re: [Paraview] Extract Point Data | Nearest Neighbor Location
>
> If they are truly the "same" why don't you forget your file2 and generate
> a polydata from the file1 as a file3?
>
> On Fri, Aug 3, 2018 at 9:41 AM Fastl, Thomas <thomas.fastl at kcl.ac.uk>
> wrote:
>
> Dear Community,
>
>
> I've got an UNSTRUCTURED_GRID (vtk-file 1) with POINT_DATA and want to
> extract the POINT_DATA at specific POINTS. However, the POINTS are
> defined in POLYDATA (vtk-file 2) and are slightly off by some rounding
> error. Thus, I presume the process should look similar to:
>
>
> 1) Find the nearest neighbors of all POINTS defined in vtk-file 2 in
> vtk-file 1
>
> 2) Transfer/Store the POINT_DATA of the nearest neighbors in vtk-file 1
>
>
> I've been searching the forum for hours, however, couldn't find a solution
> to that problem. I was wondering if there's a simple solution of doing this
> in Paraview? I'd really appreciate your help on this issue, thank you!
>
>
> Best, Thomas
>
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