[Paraview] Extraneous lines when saving large screenshots

[Utkarsh Ayachit]

By default, ParaView tries to use off-screen rendering using FBO's and
such for saving screenshots to avoid issues with overlapped windows
among other things. Depending on your OpenGL drivers, offscreen
rendering may produce slightly different results. In that case,
there's a check box in Edit|Settings (Render View) dialog, called "Use
Offscreen Rendering for Screenshots". Uncheck that, and ParaView will
no use offscreen rendering for screenshots. Does that help with issues
you are seeing with anti-aliasing?

Simply resizing the window often doesn't work if the requested
resolution is larger than the screen size. Hence we have to go with
tiling when rendering large screenshots.

Utkarsh

On Mon, Jul 27, 2009 at 5:42 PM, Tim Kostka<kostka at gmail.com> wrote:
> Thanks for the quick responses!
>
> It is a bit disconcerting that the rendering behavior when using "Save
> Screenshot" and the behavior when viewing the main window are different.
> The issue of clipping the polygon doesn't happen in the main window.  Also,
> antialiasing (at least on my Linux system) is applied in the main window but
> not applied when using "Save Screenshot."  It seems like one solution would
> be to temporarily resize the main window, render it there and save, then
> revert back to the old resolution.  Of course I don't know if there are
> limitations to doing this.
>
> Regards,
> Tim
>
> On Mon, Jul 27, 2009 at 1:25 PM, Moreland, Kenneth <kmorel at sandia.gov>
> wrote:
>>
>> At one point, I think it proposed to make the render window bigger than
>> that used for the tiling, and then clip out the part you actually use from
>> the middle of the window, thereby clipping off the boarder pixels where the
>> problem occurs.
>>
>> -Ken
>>
>>
>> On 7/27/09 1:23 PM, "Utkarsh Ayachit" <utkarsh.ayachit at kitware.com> wrote:
>>
>> That's a known issue. It also happens when saving out wireframes. The
>> problem is that we use glPolygonMode to render a surface as wireframe.
>> That produces closed polygons at window borders. When saving a large
>> screenshot, we use tiling to render an image larger than the window
>> size that introduces artifical window borders and hence those
>> extraneous lines.
>>
>> Any OpenGL experts have any idea how to overcome this issue?
>>
>> Utkarsh
>>
>> On Mon, Jul 27, 2009 at 3:13 PM, Tim Kostka<kostka at gmail.com> wrote:
>> > When I try to save a screenshot at a resolution higher than the current
>> > size, I get extraneous lines added to the object.  The screenshot
>> > attached
>> > is from trying to save a screenshot at 3x the resolution of the onscreen
>> > window.  I tried this with Paraview 3.4.0 in Windows and Linux and 3.6.1
>> > in
>> > Windows.  Using "Save animation" produced identical results.  Any ideas?
>> >
>> > Thanks,
>> > Tim Kostka
>> >
>> >
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>>    ****      Kenneth Moreland
>>     ***      Sandia National Laboratories
>> ***********
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