Re: GtkGlArea render fps is different than monitor frame rate

[Tarnyko <tarnyko tarnyko net>]

Ferenc, 

Your program's rendering is slower than the monitor nominal refresh rate, 
which is perfectly possible if your scenes are heavy. 

Please note that it could also render _faster_ (FPS higher than refresh 
rate). 

Scenes FPS are not directly tied to your monitor, unless you enable what we 
call "VSync" : i.e. your FPS are higher than 60, but you programmatically 
force it down to 60. The benefit is avoiding what we call "tearing", which 
is a display artifact that your eye could notice. 

Regards,
Tarnyko 

Ferenc Engárd writes: 

> Hi, 
>
> I have a strange issue with GtkGlArea under linux: it seems my program runs
> with a different fps than the monitor's refresh rate. (The rendering itself
> is fast, faster than 1ms.) 
>
> I use a 60Hz monitor mode, and the rendering fps is around 39.5Hz. I
> verified my monitor refresh rate with xrandr, and even with another --
> X11-EGL based -- program; it is really 60Hz. 
>
> I also measured the time interval between two render calls, and the min and
> max is around 22ms and 28ms, so it seems that I even do not drop a frame. 
>
> I do not set anything special in GtkGlArea or opengl (glSwapInterval or
> so)... 
>
> Did you encounter with such an issue? Any idea what can be the problem? 
>
> Ubuntu 16.04, unity, gtk+ 3.18.9 
>
> Thanks,
> Ferenc