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

[Taylor Braun-Jones]

Hi Felix,

I'm actually already using OpenView core. I should have mentioned this. I'm
looking for a solution to

  (1) better integrate with the Qt Quick 2 Scene Graph (e.g. layering both
under and over other Qt Quick components and applying any property that is
supported by QQuickItem like opacity, rotation, animations, etc)
  (2) help deal with multi-threading issues that VTK wasn't designed for
(caused by the fact the the Qt Quick 2 Scene Graph does all OpenGL
rendering in a dedicated render thread, separate from the main thread)

Taylor


On Tue, May 20, 2014 at 6:57 PM, Félix C. Morency
<felix.morency at gmail.com>wrote:

> 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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