[vtkusers] Integrating with Qt Quick by rendering VTK to a Framebuffer Object (FBO)

[Félix C. Morency]

Hi Taylor,

It might not be exactly what you want but I suggest you take a look at the
Kitware OpenView sources [1], more precisely the QVTKQuickItem. I also
suggest you apply the pull request #2 [2] (patch [3]) or the rendering
won't update correctly under Linux.

  [1]: https://github.com/Kitware/openview
  [2]: https://github.com/Kitware/openview/pull/2
  [3]: https://github.com/Kitware/openview/pull/2.patch

HTH,
-F


On Tue, May 20, 2014 at 5:58 PM, Taylor Braun-Jones
<taylor at braun-jones.org>wrote:

> I have solved the problem (and updated the GitHub Gist). This is what
> my QVTKFrameBufferObjectRenderer::render() method looks like now:
>
>       // Fix for differences in GL state between first call (before first
>       // rendering of the Qt Quick 2 Scene Graph) and second call. In order
>       // of most important to least.
>       glUseProgram(0);          // crucial for the cone to show up at all
> after the first render
>       glDisable(GL_DEPTH_TEST); // depth buffer fighting between the cone
> and the background without this
>       glDisable(GL_BLEND);      // doesn't seem crucial (?) but it is one
> of the differences that showed up in apitrace analysis
>
>       this->Render(); // vtkXOpenGLRenderWindow renders the scene to the
> FBO
>
> But I'd still like to know the more robust, high level, elegant VTK way to
> do this.
>
> Taylor
>
>
>
>
> On Tue, May 20, 2014 at 11:15 AM, Taylor Braun-Jones <
> taylor at braun-jones.org> wrote:
>
>> Hello vtkusers,
>>
>> I'm working on integrating VTK in into the Qt Quick Scene Graph using an
>> FBO approach.
>>
>> I currently have something that is close, but not quite there - the first
>> frame rendered to the FBO by VTK works as expected - the VTK rendered scene
>> shows up in the Qt Quick window with correct layering and Qt Quick Item
>> properties and animations work like any other Qt Quick component. Great!
>> But then... the second time the Qt Scene graph requests VTK to render to
>> the FBO nothing shows up.
>>
>> Here is my minimal example to demonstrate the problem I'm having:
>>
>> https://gist.github.com/nocnokneo/c3fb01bb7ecaf437f7d6
>>
>> It includes a README.md with some simple build instructions. To trigger a
>> second VTK-render-to-FBO, you can resize the window by one pixel (or
>> uncomment the update() call at line 64 of QVTKFrameBufferObjectItem.cpp)
>>
>> Thanks in advance for any pointers or suggestions!
>>
>> Taylor
>>
>> PS - Here are some links to provide more context and information:
>>
>>  Relevant Qt Quick 2 Docs
>> http://qt-project.org/doc/qt-5/qquickframebufferobject.html
>> http://qt-project.org/doc/qt-5/qsgsimpletexturenode.html
>>
>> http://qt-project.org/doc/qt-5/qtquick-visualcanvas-scenegraph-renderer.html
>>
>> Presentation by James Turner at Qt Developer Days
>>
>> http://www.qtdeveloperdays.com/sites/default/files/presentation_pdf/james-turner-devdays-2013-talk.pdf (video:
>> https://www.youtube.com/watch?v=BfIaTccy6HQ)
>>
>> Qt's example of what I'm trying to do except using "raw" OpenGL instead
>> of VTK and not using the QQuickFramebufferObject convenience class:
>>
>> http://qt-project.org/doc/qt-5/qtquick-scenegraph-textureinsgnode-example.html
>>
>>
>
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-- 
Félix C. Morency, M.Sc.
Plateforme d’analyse et de visualisation d’images
Centre Hospitalier Universitaire de Sherbrooke
Centre de recherche clinique Étienne-Le Bel
Local Z5-3031 | 819.346.1110 ext 16634
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