[vtkusers] QVTKOpenGLWidget and vtkImageViewer

[Utkarsh Ayachit]

What operating system is this on? I think it's some platform specific code
in Qt that causes OpenGL context to be initialized before the
QVTKOpenGLWidget is created and since it defaults to OpenGL 2.1, it doesn't
end up providing correct OpenGL context  for VTK's rendering. But I haven't
looking into it too deeply.

On Tue, Aug 1, 2017 at 2:12 PM, Olivier Commowick <
olivier.commowick at inria.fr> wrote:

> Thanks for the answer, it actually solves the problem, but I do not get
> completely why. In my code I had set the format of the widget to the right
> one. Would you have an explanation of that difference ? Basically why
> putting it before the QApplication instanciation is important ?
>
> Thanks again
> Olivier
>
> Le 1 août 2017 à 20:04, Utkarsh Ayachit <utkarsh.ayachit at kitware.com> a
> écrit :
>
> I can see one thing missing, right of the bat. You need to do the
> following before QApplication in instantiated.
>
> *QSurfaceFormat::setDefaultFormat*(format);
>
> Utkarsh
>
> On Tue, Aug 1, 2017 at 1:49 PM, Olivier Commowick <
> olivier.commowick at inria.fr> wrote:
>
>> Hi everyone,
>>
>> I have been struggling with using QVTKOpenGLWidget to display an image
>> with the vtkImageViewer. My problem is basically that the image is loaded
>> and everything created but it seems the rendering is never triggered and
>> thus the display is black.
>>
>> To summarize what I’ve done, I’ve created a vtkImageViewer3 which is the
>> same as vtkImageViewer from VTK, only changing the vtkRenderWindow to be a
>> vtkGenericOpenGLRenderWindow (required by the QVTKOpenGLWidget). I have
>> then modified the ImageViewer example from VTK to match these new classes
>> which gives the following code (see at the end). Oh, and I am using Qt5.7,
>> and VTK 8.0 release.
>>
>> Would anyone have any clue on what could make this work (i.e. actually
>> render something and display it) ?
>>
>> Thanks in advance
>> Olivier
>>
>> ——
>>
>> Main.cxx code:
>>
>> #include <QApplication>
>>
>>
>> #include "vtkImageViewer3.h"
>>
>> #include "vtkRenderWindowInteractor.h"
>>
>> #include "vtkRenderer.h"
>>
>> #include "vtkPNGReader.h"
>>
>>
>> #include "QVTKOpenGLWidget.h"
>>
>> #include <QSurfaceFormat>
>>
>>
>> int main(int argc, char** argv)
>>
>> {
>>
>>     QSurfaceFormat format = QVTKOpenGLWidget::defaultFormat();
>>
>>     format.setSamples(0);
>>
>>
>>     QApplication app(argc, argv);
>>
>>
>>     QVTKOpenGLWidget widget;
>>
>>     widget.setFormat(format);
>>
>>     widget.setEnableHiDPI(true);
>>
>>     widget.resize(256,256);
>>
>>
>>     vtkPNGReader* reader = vtkPNGReader::New();
>>
>>     std::string fname = argv[1];
>>
>>     reader->SetFileName(fname.c_str());
>>
>>
>>     vtkImageViewer3* image_view = vtkImageViewer3::New();
>>
>>     image_view->SetInputConnection(reader->GetOutputPort());
>>
>>
>>     widget.SetRenderWindow(image_view->GetRenderWindow());
>>
>>     image_view->SetupInteractor(widget.GetRenderWindow()->GetInteractor());
>>
>>
>>     image_view->SetColorLevel(138.5);
>>
>>     image_view->SetColorWindow(233);
>>
>>
>>     widget.show();
>>
>>
>>     app.exec();
>>
>>
>>     image_view->Delete();
>>
>>     reader->Delete();
>>
>>
>>     return 0;
>>
>> }
>>
>>
>>
>>
>>
>>
>>
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>
>
>
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