[vtk-developers] How to set several scalars to vtkPoint ?

[Joachim Pouderoux]

Sorry last sentence is was incomplete:

Save your grid and you will have both arrays saved in the vtk file output
for sure - and you will see that data1 is tagged as the SCALAR array.

*Joachim Pouderoux*, PhD

*Technical Expert - Scientific Computing Team*
*Kitware SAS <http://www.kitware.fr>*


2017-04-04 16:05 GMT-04:00 Joachim Pouderoux <joachim.pouderoux at kitware.com>
:

> Houssen,
>
> PointData (as CellData) is basically a set of arrays where some of them
> can be flagged as "the normal array", "the texture coordinates array", or
> even "the default scalar array".
> Only one of the arrays of the PointData can be tagged a the scalar array
> but it does not mean you cannot have more than one array that could be
> considered as a scalar array.
> Those flags are used by some VTK filters/algorithms to determine on which
> array to operate by default there are other mechanism (ie.
> SetArrayToProcess) to specify the
> array(s) to be used by a filter. See vtkDataSetAttributes
> <http://www.vtk.org/doc/nightly/html/classvtkDataSetAttributes.html>for
> more info on this mechanism.
>
> As Bill said, try this:
>
>   vtkSmartPointer<vtkIntArray> data1 = vtkSmartPointer<vtkIntArray>::New();
> data1->SetName("data1");
>   vtkSmartPointer<vtkIntArray> data2 = vtkSmartPointer<vtkIntArray>::New();
> data2->SetName("data2");
>   for (...) {data1->SetValue(idx, d1[i]); data2->SetValue(idx, d2[idx]) }
>   uGrid->GetPointdata()->AddArray(data1);
>   uGrid->GetPointdata()->AddArray(data2);
>   uGrid->GetPointdata()->SetScalars(data1); // specify that data1 is the
> array flagged as the scalar array
>
> Save your grid and you will have both arrays saved but only "data1" in the
> vtk file output for sure.
>
> Best,
>
> *Joachim Pouderoux*, PhD
>
> *Technical Expert - Scientific Computing Team*
> *Kitware SAS <http://www.kitware.fr>*
>
>
> 2017-04-02 13:12 GMT-04:00 houssen <houssen at ipgp.fr>:
>
>> May use a lookup table ? Not familiar with that but seems it's not what I
>> need ?!...
>>
>> Somebody knows how to get back to this broken link ttp://
>> article.gmane.org/gmane.comp.lib.vtk.user/6761/match=points+scalar+color
>> I got from http://public.kitware.com/pipermail/vtkusers/2003-August/019
>> 748.html
>>
>>
>> Le 2017-04-02 18:39, houssen a écrit :
>>
>>> KO ! Does not work (realize I tried this before !) => I only get
>>> data1 OR data2 (never both of them) in the written .vtu file...
>>> It is possible to make this work or to create a N-sized-vector.
>>>
>>> BTW, data1 is "pressure", data2 is "velocity" (that is data 1 and 2
>>> are not related to each other)
>>>
>>> Franck
>>>
>>> Le 2017-04-02 18:24, Bill Lorensen a écrit :
>>>
>>>> Try
>>>> uGrid->GetPointdata()->AddArray(data2);
>>>>
>>>>
>>>> On Sun, Apr 2, 2017 at 12:01 PM, houssen <houssen at ipgp.fr> wrote:
>>>>
>>>>> Hello,
>>>>>
>>>>> How to set several scalars to vtkPoint ?
>>>>>
>>>>> Seems vtkDataPoint scratchs the previous scalar array ?!
>>>>>
>>>>> vtkSmartPointer<vtkIntArray> data1 = vtkSmartPointer<vtkIntArray>::
>>>>> New();
>>>>> data1->SetName("data1");
>>>>> vtkSmartPointer<vtkIntArray> data2 = vtkSmartPointer<vtkIntArray>::
>>>>> New();
>>>>> data2->SetName("data2");
>>>>> for (...) {data1->SetValue(idx, d1[i]); data2->SetValue(idx, d2[idx]) }
>>>>> uGrid->GetPointdata()->SetScalars(data1); // OK
>>>>> uGrid->GetPointdata()->SetScalars(data2); // data2 scratch data1 ?!
>>>>>
>>>>> uGrid->GetPointdata()->SetActiveScalar("data1") does not do what I
>>>>> need :
>>>>> seems that it activate data1 back but "scratch" data2 back.
>>>>>
>>>>> uGrid is a vtkUnstructuredGrid : the final goal is to write the grid
>>>>> to a
>>>>> file (with vtkWriter). In this file, I'd like to have BOTH data1 and
>>>>> data2
>>>>> for points.
>>>>> I only get either one or the other... How to get both ?
>>>>>
>>>>> Also tried to create a N-sized-vector (N=2 or 4) to associate to the
>>>>> vtkPoint : does not work as it seems vector dimension MUST be 3. I
>>>>> somebody
>>>>> knows a solution to attach a N-sized-vector to a vtkPoint, it could
>>>>> solve my
>>>>> problem
>>>>>
>>>>> Franck
>>>>>
>>>>> PS : found nothing relevant on the web, targetting VTK-7.
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