The NetCDF Generic/CF reader has an option named “Output Type” that you can use 
to force the output to a vtkImageData. Then Cory’s original programmable filter 
will work, and you won’t have to deal with the coordinates.

-Ken

From: ParaView <paraview-boun...@public.kitware.com> on behalf of Cory Quammen 
<cory.quam...@kitware.com>
Date: Wednesday, May 2, 2018 at 11:19 AM
To: "j.vanengel...@uu.nl" <j.vanengel...@uu.nl>
Cc: "paraview@public.kitware.com" <paraview@public.kitware.com>
Subject: [EXTERNAL] Re: [Paraview] generic NetCDFreader support for CellData

On Wed, May 2, 2018 at 11:37 AM Engelen, J. van (Joeri) 
<j.vanengel...@uu.nl<mailto:j.vanengel...@uu.nl>> wrote:
Thank you Cory,

I sense this solution might work. However, the type of my data is “Rectilinear 
Grid”, not sure if that increases the complexity (dx = 1000, dy = 1000, dz = 1).

Ah. From the documentation: "To define a 
vtkRectilinearGrid<https://www.vtk.org/doc/nightly/html/classvtkRectilinearGrid.html>,
 you must specify the dimensions of the data and provide three arrays of values 
specifying the coordinates along the x-y-z axes". It should be a similar 
script, but you'd have to add an additional X, Y, and Z position at the end of 
those coordinate arrays. So your script would look more like:

dims = inputs[0].GetDimensions()

ext = inputs[0].GetExtent()

output.SetDimensions(dims[0]+1, dims[1]+1, dims[2]+1)

output.SetExtent(ext[0], ext[1]+1, ext[2], ext[3]+1, ext[4], ext[5]+1)

inputPd = inputs[0].GetPointData()

outputCd = output.GetCellData()

outputCd.SetScalars(inputPd.GetScalars())



# Set coordinates

xCoords = inputs[0].GetXCoordinates().NewInstance()

xCoords.DeepCopy(inputs[0].GetXCoordinates())

xCoords.InsertNextValue(1.0) # Should a reasonable x value for your dataset 
larger than previous max x

output.SetXCoordinates(xCoords)



yCoords = inputs[0].GetYCoordinates().NewInstance()

yCoords.DeepCopy(inputs[0].GetYCoordinates())

yCoords.InsertNextValue(1.5) # Should be a reasonable like the x coordinate

output.SetYCoordinates(yCoords)



zCoords = inputs[0].GetZCoordinates().NewInstance()

zCoords.DeepCopy(inputs[0].GetZCoordinates())

zCoords.InsertNextValue(1.0) # Should be a reasonable like the z coordinate

output.SetZCoordinates(zCoords)


Some extent information also needs to be supplied, but I'm not entirely clear 
on how to do that correctly.


A better solution would be to add an option to the reader to take care of this 
for you if that is reasonable for your data.

Best,
Cory


Regardless, the script you provided does not give me output and it also does 
not throw an error, so I’m left a bit in the dark here.

From: Cory Quammen 
[mailto:cory.quam...@kitware.com<mailto:cory.quam...@kitware.com>]
Sent: Wednesday, May 02, 2018 5:01 PM
To: Engelen, J. van (Joeri)
Cc: paraview@public.kitware.com<mailto:paraview@public.kitware.com>
Subject: Re: [Paraview] generic NetCDFreader support for CellData

Joeri,

You can try the "Point Data to Cell Data" filter, but that averages the point 
data and places the results in the cell data. You may wind up with some 
incorrect values using that approach.

Better would be to use a "Progammable Filter" to resize the cartesian grid read 
by the NetCDF reader and treat the point data as cell data. That is a bit 
involved, but not terrible. Set the Script to


dims = inputs[0].GetDimensions()

ext = inputs[0].GetExtent()

output.SetDimensions(dims[0]+1, dims[1]+1, dims[2]+1)

output.SetExtent(ext[0], ext[1]+1, ext[2], ext[3]+1, ext[4], ext[5]+1)

inputPd = inputs[0].GetPointData()

outputCd = output.GetCellData()

outputCd.SetScalars(inputPd.GetScalars())


This assumes that the NetCDF reader is producing a vtkImageData (you can check 
under the Information panel) which would report the Type: of the data set as 
"Image (Uniform Rectilinear Grid).

HTH,
Cory

On Wed, May 2, 2018 at 10:17 AM Engelen, J. van (Joeri) 
<j.vanengel...@uu.nl<mailto:j.vanengel...@uu.nl>> wrote:
Hi,

I was wondering whether it is possible to read NetCDF files as CellData.

I have categorial data on Cartesian coordinates that I want to visualize. To be 
more specific, the data represents lithologies of the subsurface. So 1 = sand, 
3 = clay, 5 = rock.
The problem is that my file is automatically interpreted as PointData. To 
render this PointData, Paraview than consequently interpolates to achieve cell 
values.
With most variables that is not such a problem, but here it is. If I have sand 
(1) overlying rock (5), Paraview shows me clay (3).

Also, the information available to me was ambiguous,
-this source says it is probably not possible:
https://public.kitware.com/pipermail/paraview/2017-September/040984.html
-this states it is possible return Cell Data information:
https://www.paraview.org/ParaView/Doc/Nightly/www/py-doc/paraview.simple.NetCDFReader.html

I tried converting my data from NetCDF to a .vtr file in Python, but this 
resulted in more problems than solutions. (Just gave me very glitched 
rendering).

So I have two questions:
-Is this possible?
-Are there any workarounds you can think of to get my data as CellData in 
Paraview?

I’m using Paraview v5.4.1 on Windows 7.

Kind regards,
Joeri
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--
Cory Quammen
Staff R&D Engineer
Kitware, Inc.


--
Cory Quammen
Staff R&D Engineer
Kitware, Inc.
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