[vtkusers] Probing unstructured point data onto an unstructured grid

[Goodwin Lawlor]

Hi Alex,

A couple of things might work:

1. You could use either vtkShepardMethod or vtkGaussianSplatter to sample
the brick_8.ipr data onto a volume. You could then probe this volume with
the brick_8.vtk data

2. It looks like the brick_8.ipr could be topologically regular. If thats
the case, then use vtkStructuredGrid to hold your brick_8.ipr data. You
could then probe the structured grid.

Attached is what the structured grid vtk file would look like. You have to
be careful with the point order... Just use vtkStructuredGridReader instead
of vtkUnstructuredGridReader

The vtk data is outside the ipr data so it wont be able to probe anyway- I
assume the bricks are apart of a larger mesh so this wont matter (except at
the edges). The "splatting" above might let you extrapolate.

HTH

Goodwin


----- Original Message -----
From: "Alex Lennon" <alennon at tcd.ie>
To: "Prabhu Ramachandran" <prabhu at aero.iitm.ernet.in>
Cc: "Vtkusers" <vtkusers at public.kitware.com>
Sent: Thursday, November 14, 2002 11:05 AM
Subject: RE: [vtkusers] Probing unstructured point data onto an unstructured
grid


> Hi Prabhu,
>
> Sorry if the mail was unclear.
>
> >>2. The points in your brick_8.ipr do not coincide with the points in
> >> brick_8.vtk.  Is this what you want?
>
> The 'ipr' file contains the finite element integration points. These are
> simply interpolated points inside a finite element at which numerical
> integration is performed (this is why they do not coincide with the points
> in the 'vtk' file). All quantities are calculated at these points and not
at
> the nodes of the element (vertices of the cell in the 'vtk' file).
>
> >>1. brick_8.ipr defines no volumes and only points.  Probing with this
> >> will only give you the values at these points.  Visualizing these
> >> points will not be any fun, you'll just see a bunch of tiny coloured
> >> points.  If you want to probe the volume then you need to probe with
> >> another volume.
>
> The point data in the 'ipr' file already contains the results---what I'd
> like to do is to interpolate from the point data in the 'ipr' file to the
> nodes of the 'vtk' file (i.e. the reverse of the above). I have written
code
> to do this before writing out the vtk file from my finite element
> application but I would like to be able to do this when selecting
different
> subsets of integration points as I visualise the data (e.g. based on
> material properties of the finite element model).
>
> I tried vtkPointDataToCellData but it still gave 0's. Anyway, it's the
> points making up the cell in the 'vtk' file that I would like to map the
> data to. If a probe filter is not the correct way of going about this I'd
> appreciate any suggestions as to what is.
>
> Thanks for the help,
>
> Alex
>
> Trinity Centre for Bioengineering
> Dept. Mechanical Engineering
> Trinity College
> Dublin 2
> Ireland
>
> email: alennon at tcd.ie
> Tel:   +353-1-608 2396
> Fax:   +353-1-679 5554
> http://www.biomechanics.ie
>
> -----Original Message-----
> From: Prabhu Ramachandran [mailto:prabhu at aero.iitm.ernet.in]
> Sent: Wednesday, November 13, 2002 7:07 PM
> To: Alex Lennon
> Cc: Vtkusers
> Subject: Re: [vtkusers] Probing unstructured point data onto an
> unstructured grid
>
>
> >>>>> "AL" == Alex Lennon <alennon at tcd.ie> writes:
>
>     AL> Hi, I'm using vtk to visualise results of finite element
>     AL> simulations and would like to sample integration point results
>     AL> to nodes. To do this I'm using two separate unstructured grid
>     AL> files: one with the integration points and their associated
>     AL> data, and the other with just the nodes (i.e. points) and
>     AL> elements (i.e. cells). I'm working in python (which I'm pretty
>
> I'm not completely clear on what exactly you want to do, but are you
> simply trying to convert your PointData to CellData?  If so, you dont
> need to go through all this probing.  Simply use the
> vtkPointDataToCellData class to do the job.
>
> If that is not the case I am confused with a few things in your data:
>
>  1. brick_8.ipr defines no volumes and only points.  Probing with this
>  will only give you the values at these points.  Visualizing these
>  points will not be any fun, you'll just see a bunch of tiny coloured
>  points.  If you want to probe the volume then you need to probe with
>  another volume.
>
>  2. The points in your brick_8.ipr do not coincide with the points in
>  brick_8.vtk.  Is this what you want?
>
>  3. I am not entirely sure if probing will work the way you want with
>  cell data and point data.
>
> cheers,
> prabhu
>
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