[vtkusers] [vtk-developers] QVTKOpenGLWidget + SSAA pass breaks depth peeling

[Simon Esneault]

Hello Allie,

Thanks for the explanation, that make complete sense, and it works !

Simon

2018-02-16 22:39 GMT+01:00 Allie Vacanti <allison.vacanti at kitware.com>:

> Hi Simon,
>
> This is intended behavior. Setting a pass on the renderer bypasses the
> renderer's internal settings, and only the specified pass will be rendered.
> This means that the call to l_renderer->SetUseDepthPeeling(true); has no
> effect; only the l_ssaa render pass will be executed.
>
> Your l_ssaa pass delegates to an instance of vtkRenderPassStepsPass, which
> by default uses vtkTranslucentPass for rendering the translucent geometry
> -- this only does basic alpha blending, not depth peeling.
>
> What you want to do is replace the translucent pass with one that performs
> depth peeling. Something like this should work:
>
>     ...
>
>     // setup SSAA pass
>     vtkSmartPointer<vtkRenderStepsPass> l_basic_passes = vtkSmartPointer<
> vtkRenderStepsPass>::New();
>     vtkSmartPointer<vtkSSAAPass> l_ssaa = vtkSmartPointer<vtkSSAAPass>::
> New();
>     l_ssaa->SetDelegatePass( l_basic_passes );
>     l_renderer->SetPass( l_ssaa );
>
>     // Enable depth peeling. This pass is defined in the
> vtkRenderingOpenGL2 module.
>     vtkSmartPointer<vtkDualDepthPeelingPass> l_peel = vtkSmartPointer<
> vtkDualDepthPeelingPass>::New();
>     l_basic_passes->SetTranslucentPass(l_peel);
>
>     ...
>
> If you have issues with the dual depth peeling pass, try the older
> vtkDepthPeelingPass. It's a bit slower, but still works.
>
> HTH,
> Allie
>
> On Tue, Feb 13, 2018 at 3:54 AM, Simon Esneault <simon.esneault at gmail.com>
> wrote:
>
>> Hello VTK community
>>
>> Is seems adding an SSAA rendering pass breaks the depth peeling process.
>> Attached is an example that highlight the problem. When commenting out the
>> line 64 (l_renderer->SetPass( l_ssaa ); the translucent geometry is
>> rendered correctly, but the result is not anti-aliased.
>>
>> With SSAA pass -> Depth Peeling broken : https://cdn.pbrd.co/images/H
>> 7qnZxC.png
>> Without SSAA pass -> Depth Peeling ok : https://cdn.pbrd.co/images/H
>> 7qnvE9.png
>>
>> Shall I fill a bug for this ?
>>
>> Thanks
>>
>> --
>> ------------------------------------------------------------------
>> Simon Esneault
>> Rennes, France
>> ------------------------------------------------------------------
>>
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Simon Esneault
Rennes, France
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