[Paraview] Accessing a specific variable in Python Programmable Filter

[Burlen Loring]

correction, Dave D. just pointed out to me that since PV 4.0 the shallow 
copy is no longer needed because of the VTK 6.0 pipeline improvements.

On 05/16/2014 02:07 PM, Burlen Loring wrote:
> By the way, the example following that is buggy as well, when you 
> apply an internal filter you first need to shallow copy the input.
>
> I fixed both of these, although I think these examples(ones in 
> Examples section) are not great ones in the first place and don't add 
> much to the already pretty comprehensive examples preceding them, I  
> would vote to remove them. However, I'll leave this up to the real pv 
> developers....
>
> On 05/16/2014 01:43 PM, Su, Simon M CTR USARMY ARL (US) wrote:
>> Thanks Burlen
>> -simon
>>
>> ------------------------------------------------------------------------
>> *From:* Burlen Loring [bloring at lbl.gov]
>> *Sent:* Friday, May 16, 2014 4:23 PM
>> *To:* Su, Simon M CTR USARMY ARL (US); paraview at paraview.org
>> *Subject:* Re: [Paraview] Accessing a specific variable in Python 
>> Programmable Filter
>>
>>> =============================
>>> input  =self.GetPolyDataInput();
>>> output =self.GetPolyDataOutput();
>>>   
>>> colors = vtk.vtkUnsignedCharArray();
>>> colors.SetNumberOfComponents(3);
>>> colors.SetName("Colors");
>>>   
>>> numPoints =input.GetNumberOfPoints()
>>> for  iin  range(0, numPoints):
>>>      colors.InsertNextTuple3(255,0,0);
>>>   
>>> output=input
>>> output.GetPointData().AddArray(colors)
>>> ===============================
>> Not sure how this got on the wiki but this is an example of what 
>> *not* to do!!
>>
>> In a VTK filter one's never supposed to modify the input.
>>> output=input
>>> output.GetPointData().AddArray(colors)
>> This is exactly what's done here. Of course you're not going to find 
>> the array in the filter's output if you're adding it to the input!
>>
>> This code can be fixed by removing the output=input line. With that 
>> change you should be able to see the array in downstream filters. 
>> note, in python 2 range actually generates a list with all the values 
>> in it, while xrange creates an iterator which is far more efficient. 
>> To actually use the colors you'll also have to uncheck the map 
>> scalars check box in the display properties.
>>
>> input = self.GetPolyDataInput();
>>
>> output = self.GetPolyDataOutput();
>>
>> colors = vtk.vtkUnsignedCharArray();
>>
>> colors.SetNumberOfComponents(3);
>>
>> colors.SetName("Colors");
>>
>> numPoints = input.GetNumberOfPoints()
>>
>> for i in xrange(0, numPoints):
>>
>> colors.InsertNextTuple3(0,255,0);
>>
>> output.GetPointData().AddArray(colors)
>>
>> del colors
>>
>>
>>
>> On 05/16/2014 12:46 PM, Su, Simon M CTR USARMY ARL (US) wrote:
>>> Hello,
>>>
>>> After staring at 
>>> http://www.paraview.org/Wiki/Python_Programmable_Filter for a while, 
>>> the way to access the data for a specific variable name still eludes 
>>> me. This is the python code from the wiki on Add the Colors variable 
>>> to a PolyData
>>>
>>> =============================
>>> input  =self.GetPolyDataInput();
>>> output =self.GetPolyDataOutput();
>>>   
>>> colors = vtk.vtkUnsignedCharArray();
>>> colors.SetNumberOfComponents(3);
>>> colors.SetName("Colors");
>>>   
>>> numPoints =input.GetNumberOfPoints()
>>> for  iin  range(0, numPoints):
>>>      colors.InsertNextTuple3(255,0,0);
>>>   
>>> output=input
>>> output.GetPointData().AddArray(colors)
>>> ===============================
>>>
>>> How do I from the next filter, access the variable name "Colors" 
>>> that I created?
>>>
>>> Any help is much appreciated.
>>>
>>> thanks
>>> -simon
>>>
>>>
>>> _______________________________________________
>>> Powered bywww.kitware.com
>>>
>>> Visit other Kitware open-source projects athttp://www.kitware.com/opensource/opensource.html
>>>
>>> Please keep messages on-topic and check the ParaView Wiki at:http://paraview.org/Wiki/ParaView
>>>
>>> Follow this link to subscribe/unsubscribe:
>>> http://www.paraview.org/mailman/listinfo/paraview
>>
>
>
>
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html
>
> Please keep messages on-topic and check the ParaView Wiki at: http://paraview.org/Wiki/ParaView
>
> Follow this link to subscribe/unsubscribe:
> http://www.paraview.org/mailman/listinfo/paraview

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.paraview.org/pipermail/paraview/attachments/20140516/2fa1d682/attachment.html>