[vtkusers] Flat interpolation under OpenGL2 backend

Tue Feb 23 03:59:21 EST 2016

Hello again!
Adding those lines of code solved the issue, thank you!
I was missing the call to setactivescalar after the geometry filter, what a
dumb error!

The issue is solved and now I can do what I wanted. Thank you all again.
Fernando.

2016-02-22 15:51 GMT+01:00 Simon ESNEAULT <simon.esneault at gmail.com>:

> Hello,
>
> If the data is in there, a combination of :
> SetScalarModeToUseCellData()
> GetCellData()->SetActiveScalars( "TEMP" );
> should probably do the trick
>
> The SetActiveScalars( "TEMP" ) should be called on the output of the
> geometryFIlter which -I think- is not the case in the code that was posted:
>
> Maybe something like this :
>
> *************************************
> geometryFilter->Update();
> vtkPolyData* polydata = geometryFilter->GetOutput();
> polydata->GetCellData()->SetActiveScalars( "TEMP" );
> colorMapper->SetInputData( polydata );
> colorMapper->ScalarVisibilityOn();
> colorMapper->SetScalarModeToUseCellData();
> colorMapper->SetScalarRange(297, 637);
> **************************************
> ?
>
> Simon
>
>
>
>
>
>
>
> 2016-02-22 15:21 GMT+01:00 Fernando Nellmeldin <
> f.nellmeldin at open-engineering.com>:
>
>> Hi, thank you for your response Simon.
>> I tried your suggestions. Adding SetScalarModeToUseCellData didn't solve
>> the problem :( (still I'm seeing all the model in white)
>> I saved my results to load them in ParaView and indeed I can see a new
>> Cell Data named "TEMP" with the values of the Point Data as I wish.
>> Thus, I think that the point2celldata is working properly, and I have
>> only a problem of configuring something to see it, but where?
>>
>> Any thoughs?
>>
>> Thank you.
>>
>> 2016-02-22 14:28 GMT+01:00 Simon ESNEAULT <simon.esneault at gmail.com>:
>>
>>> Hello,
>>>
>>> Not sure, but maybe a call to
>>> SetScalarModeToUseCellData()
>>> is needed on the mapper ?
>>> You should try to save/load the dataset in paraview after it is
>>> processed to see what's going on with the cell/point data :)
>>>
>>> Good luck
>>> Simon
>>>
>>>
>>>
>>> 2016-02-22 13:23 GMT+01:00 Fernando Nellmeldin <
>>> f.nellmeldin at open-engineering.com>:
>>>
>>>> Hello again.
>>>> Yes, you understood the issue perfectly. And I understand the reason as
>>>> of why is not working anymore, thank you for the great explanation.
>>>>
>>>> After your advise, I tried using vtkPointDataToCellData, but without
>>>> success.
>>>> Here is one small example I wrote. If I activate the line #define
>>>> USE_P2C, I can't see any color (everything is light gray). If that line is
>>>> commented, everything works as expected.
>>>> Do you know what I am missing?
>>>>
>>>>
>>>> #include <vtkSmartPointer.h>
>>>> #include <vtkDataSetMapper.h>
>>>> #include <vtkActor.h>
>>>> #include <vtkPointDataToCellData.h>
>>>> #include <vtkUnstructuredGrid.h>
>>>> #include <vtkUnstructuredGridGeometryFilter.h>
>>>> #include <vtkGeometryFilter.h>
>>>> #include <vtkXMLUnstructuredGridReader.h>
>>>> #include <vtkRenderer.h>
>>>> #include <vtkRenderWindow.h>
>>>> #include <vtkPointData.h>
>>>> #include <vtkCellData.h>
>>>> #include <vtkRenderWindowInteractor.h>
>>>> int main()
>>>> {
>>>> // Read the grid
>>>> std::string filename = "D:/model.vtu";
>>>> std::string fieldname = "TEMP";
>>>> vtkSmartPointer<vtkXMLUnstructuredGridReader> reader =
>>>> vtkSmartPointer<vtkXMLUnstructuredGridReader>::New();
>>>> reader->SetFileName(filename.c_str());
>>>> reader->Update();
>>>> vtkSmartPointer<vtkUnstructuredGrid> model = reader->GetOutput();
>>>>
>>>> vtkSmartPointer<vtkDataSetMapper> colorMapper =
>>>> vtkSmartPointer<vtkDataSetMapper>::New();
>>>> vtkSmartPointer<vtkActor> colorActor = vtkSmartPointer<vtkActor>::New();
>>>> vtkSmartPointer<vtkGeometryFilter> geometryFilter =
>>>> vtkSmartPointer<vtkGeometryFilter>::New();
>>>>
>>>> //============ BEGIN OF SECTION OF INTEREST
>>>> // Convert point to cell data
>>>> vtkSmartPointer<vtkPointDataToCellData> point2CellData =
>>>> vtkSmartPointer<vtkPointDataToCellData>::New();
>>>> point2CellData->PassPointDataOn();
>>>> point2CellData->SetInputData(model);
>>>> point2CellData->Update();
>>>>
>>>> #define USE_P2C
>>>> #ifdef USE_P2C
>>>> // Neither of these "setActiveScalars" makes any difference
>>>> //model->GetCellData()->SetActiveScalars(fieldname.c_str());
>>>> //model->GetPointData()->SetActiveScalars(fieldname.c_str());
>>>> geometryFilter->SetInputData(point2CellData->GetOutput());
>>>> geometryFilter->SetInputArrayToProcess(0, 0, 0,
>>>> vtkDataObject::FIELD_ASSOCIATION_CELLS, fieldname.c_str()); // cells
>>>> because I transfered the data
>>>> #else
>>>> model->GetPointData()->SetActiveScalars(fieldname.c_str());
>>>> geometryFilter->SetInputData(model);
>>>> geometryFilter->SetInputArrayToProcess(0, 0, 0,
>>>> vtkDataObject::FIELD_ASSOCIATION_POINTS, fieldname.c_str());
>>>> #endif
>>>>
>>>> colorMapper->SetInputConnection(geometryFilter->GetOutputPort());
>>>>
>>>> //============ END OF SECTION OF INTEREST
>>>>
>>>> colorMapper->SetScalarRange(297, 637); //hardcoded to reduce code length
>>>> colorActor->SetMapper(colorMapper);
>>>> colorMapper->ScalarVisibilityOn();
>>>>
>>>> // Usual rendering stuff, nothing of interest from here onwards
>>>> //Create a renderer, render window, and interactor
>>>> vtkSmartPointer<vtkRenderer> renderer =
>>>> vtkSmartPointer<vtkRenderer>::New();
>>>> vtkSmartPointer<vtkRenderWindow> renderWindow =
>>>> vtkSmartPointer<vtkRenderWindow>::New();
>>>> renderWindow->AddRenderer(renderer);
>>>> vtkSmartPointer<vtkRenderWindowInteractor> renderWindowInteractor =
>>>> vtkSmartPointer<vtkRenderWindowInteractor>::New();
>>>> renderWindowInteractor->SetRenderWindow(renderWindow);
>>>> //Add the actor to the scene
>>>> renderer->AddActor(colorActor);
>>>> renderer->SetBackground(.3, .6, .3); // Background color green
>>>> //Render and interact
>>>> renderWindow->Render();
>>>> renderWindowInteractor->Start();
>>>> return EXIT_SUCCESS;
>>>> }
>>>>
>>>>
>>>> Thank you!.
>>>>
>>>> 2016-02-18 17:05 GMT+01:00 Ken Martin <ken.martin at kitware.com>:
>>>>
>>>>> Hello Fernando,
>>>>>
>>>>> Making sure that I understand the issue. Essentially you have defined
>>>>> scalars/colors on the points of a triangle. With phong shading the colors
>>>>> interpolate across the triangle. With flat shading on the old backend, the
>>>>> system takes the color of the first point and uses that for the entire
>>>>> triangle. On the new backend the colors are still interpolated across the
>>>>> triangle.  Is that the issue you see?
>>>>>
>>>>> If so, then the issue is that on the new backend I am interpreting
>>>>> shading to only mean lighting and normal calculations while in the old
>>>>> backend it seems to include vertex color properties (but not other
>>>>> properties such as tcoords, hmm wonder what happens with flat shading and
>>>>> texture based coloring) In modern OpenGL (version 3.2 ) you can specify
>>>>> flat versus smooth interpolation by attribute. So normals could be flat
>>>>> while colors are smooth. Without requiring OpenGL 3.2 we would need to
>>>>> rebuild the VBO each time you switch between flat and smooth, basically
>>>>> treating flat shading as if you had cell colors instead of point colors.
>>>>>
>>>>> If backward compatibility was not an issue :-) I would suggest moving
>>>>> to require OpenGL 3.2 and then modifying vtkProperty so that people can
>>>>> independently specify if they want normals/colors/etc to be
>>>>> flat/smooth/perspective.
>>>>>
>>>>> One stopgap, you could use vtkPointDataToCellData to essentially
>>>>> accomplish what you want in either back end.
>>>>>
>>>>> Thanks
>>>>> Ken
>>>>>
>>>>>
>>>>>
>>>>> On Thu, Feb 18, 2016 at 10:14 AM, Fernando Nellmeldin <
>>>>> f.nellmeldin at open-engineering.com> wrote:
>>>>>
>>>>>> Hello friends.
>>>>>>
>>>>>> In our application, we want to allow the user to alternate between a
>>>>>> flat and a smooth shading of the colors in an actor. To do this, we have a
>>>>>> option that allows the user to call setInterpolationToFlat() or
>>>>>> setInterpolationToPhong() in the property of the vtkactor.
>>>>>>
>>>>>> The problem is that the call to set flat is not working, there is no
>>>>>> change and the actor is always rendered smooth.
>>>>>>
>>>>>> I've tried with VTK 6.3.0 and VTK 7.0.0 under OpenGL2 backend. In VTK
>>>>>> 5.10 (using the old opengl), this works as expected.
>>>>>>
>>>>>> And please note that in the three cases, the code is exactly the
>>>>>> same. Well, except the connection between the ugrid and the geometry filter
>>>>>> that I have the usual if:
>>>>>> #if VTK_MAJOR_VERSION <= 5
>>>>>> geometryFilter->SetInputConnection(m_model->GetProducerPort());
>>>>>> #else
>>>>>> geometryFilter->SetInputData(m_model);
>>>>>> #endif
>>>>>>
>>>>>> Therefore, is the support of flat interpolation dropped, or I have to
>>>>>> add something to make it work under OpenGL2 backend?
>>>>>>
>>>>>> Thank you!
>>>>>>
>>>>>>
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>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Ken Martin PhD
>>>>> Chairman & CFO
>>>>> Kitware Inc.
>>>>> 28 Corporate Drive
>>>>> Clifton Park NY 12065
>>>>> 518 371 3971
>>>>>
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>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> *Fernando NELLMELDIN*
>>>> Software Engineer
>>>> *_______________________________________________________________*
>>>>
>>>> *Open Engineering s.a.*
>>>>
>>>> Rue Bois Saint-Jean 15/1
>>>> B-4102 Seraing (Belgium)
>>>> Tel: +32.4.353.30.34
>>>>
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>>>>
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>>>> Visit other Kitware open-source projects at
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>>>>
>>>
>>>
>>> --
>>> ------------------------------------------------------------------
>>> Simon Esneault
>>> Rennes, France
>>> ------------------------------------------------------------------
>>>
>>
>
>
> --
> ------------------------------------------------------------------
> Simon Esneault
> Rennes, France
> ------------------------------------------------------------------
>
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