[Paraview] Polyhedral Cells: Rendering Problem with OpenGL...

[Ken Martin]

Basically it is OpenGL, in that OpenGL doesn't automatically tessellate
concave polygons. Making VTK always examine every polygon to determine if
it is  concave would be a performance hit for everyone, so we leave it up
to developers to use a triangle filter if they need it.

Thanks
Ken

On Tue, Oct 18, 2016 at 9:11 AM, Stefan Melber <Stefan.Melber at dlr.de> wrote:

> Hi Martin,
>
> i tried the triangle filter in all cases - and yes - i works in all three
> cases.
>
> So is this "problem" of concave polygons inside VTK or in OpenGL?
>
> Best regards,
>
>       Stefan
>
> I'm not sure if this is your issue, but you might try using a triangle
> filter on your data. For OpenGL we do not guarantee correct rendering of
> concave polygons. The triangle filter will convert a concave polygon into
> convex triangles which should render correctly.
>
> On Tue, Oct 18, 2016 at 2:20 AM, Stefan Melber <Stefan.Melber at dlr.de>
> wrote:
>
>> Hi,
>>
>> i found a rendering problem with cuts through polyhedral cells depending
>> on which rendering backend is used. For example in PV 5.1.2 compiled with
>>
>> VTK_RENDERING_BACKEND = OpenGL
>>
>> a cut looks like error.opengl.v5_1_2.png - there is a wrong shading and
>> some facets coming from the wrong starting point.
>>
>> Switching to OpenGL2 everything is fine (error.opengl2.v5_1_2.png). This
>> problem is the same with ParaView 5.2.0RC1 and OpenGL or OpenGL2 - however
>> there seems to be an additional (smaller) problem using OpenGL2: there are
>> some lines drawn outside of the shell - see error.opengl2.v5_2_0rc1.png
>> (cutted on a different position).
>>
>> The example cell is for testing is attached as "error.vtk" - cut e.g. in
>> x-direction on different positions to get the described effects.
>>
>> Best regards,
>>
>>        Stefan
>>
>>
>> System:
>> o OpenSuse Tumbleweed
>> o Kernel: 4.7.6-1
>> o Linux 64 bit
>> o NVidia Quadro 4000 / NV Driver v367.44
>>
>>
>>
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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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-- 
Ken Martin PhD
Chairman & CFO
Kitware Inc.
28 Corporate Drive
Clifton Park NY 12065
518 371 3971

This communication, including all attachments, contains confidential and
legally privileged information, and it is intended only for the use of the
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action taken in reliance on it is prohibited and may be unlawful. If you
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