[vtkusers] Why do my vtkRenderWindows divide up the frame rate?

[David Gobbi]

Hi Thomas,

You can try playing around with the vsync in your driver settings (for
example, if you have an NVidia GPU then run nvidia-settings).

 - David

On Tue, Oct 13, 2015 at 11:22 AM, Kirchner, Thomas <
t.kirchner at dkfz-heidelberg.de> wrote:

> Hi David,
>
> thank you for taking the time.
> SwapBuffers changed nothing on the speed (still 60/numberOfRenderWindows
> fps). Although weirdly this is only the case on my ubuntu system -- on my
> Macbook this doesnt occur at all (60fps on all 10 renderwindows).
> Also, if i completely turn off DoubleBuffering it doesnt occur, but i do
> get the typical image artifacts.
>
> - Thomas
>
> ________________________________________
> From: David Gobbi [david.gobbi at gmail.com]
> Sent: Tuesday, October 13, 2015 3:09 AM
> To: Kirchner, Thomas
> Cc: vtkusers at vtk.org
> Subject: Re: [vtkusers] Why do my vtkRenderWindows divide up the frame
> rate?
>
> Hi Thomas,
>
> The default behavior of vtkRenderWindow is to wait for the vblank before
> swapping the buffers.  So with multiple RenderWindows, the result is slow
> rendering and, even worse, the windows aren't synchronized.  You can try
> the following work-around:
>
> For each window, call SwapBuffersOff() before calling Render().  This
> allows each window to do its rendering without swapping the buffers.
>  Then, call SwapBuffersOn() and Frame() for each window.  This will
> synchronize the buffer swapping.
>
>  - David
>
>
> On Mon, Oct 12, 2015 at 5:50 PM, Kirchner, Thomas <
> t.kirchner at dkfz-heidelberg.de<mailto:t.kirchner at dkfz-heidelberg.de>>
> wrote:
> Hello everyone,
>
> i am trying to get multiple vtkRenderWindows to render (4 different
> image streams in my case) simultaneously at 60fps which seems to be the
> frame rate limit for one single vtkRenderWindow (at least with my
> screen). It appears to me that multiple render windows in the same
> application share those 60fps ... e.g. yielding exactly 15fps for 4
> windows.
> If i just start a new application for each window this does not occur
> (which gives me hope but doesn't help)
>
> I can't figure out why this frame rate limit is "shared" and i dont think
> this behavior is intended. But maybe you guys know how i can avoid this
> effect?
> (my simple example, mostly stitched together from other example code is
> attached)
>
> Any help would be greatly appreciated.
>
> Thanks in advance
> Thomas
>
> --
> Thomas Kirchner
> German Cancer Research Center (DKFZ)
> Division Medical and Biological Informatics
> E131 - Computer-assisted Interventions
>
> Im Neuenheimer Feld 280
> 69120 Heidelberg, Germany
> Tel.: +49 (0) 6221 / 42-3543<tel:%2B49%20%280%29%206221%20%2F%2042-3543>
>
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