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Vsync

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Revision as of 06:15, 16 March 2015 by Hooray (Talk | contribs) (http://forum.flightgear.org/viewtopic.php?f=37&t=25486&p=235404#p235404)

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Cquote1.png FPS is not a good performance metric. If you have vsync turned on in your

driver, a very tiny change in the time of an operation can make a big fps
difference. Also, everyone has different hardware... It's more useful to
look at the OSG statistics (choose "Cycle On-Screen Statistics" twice) and
report the times reported for each traversal. Or include a screenshot of
them.


Cquote2.png
Cquote1.png Almost all LCDs have a native refresh rate of 60 FPS which works out to about

16.66 milliseconds per frame. There is a frame rate at which the human eye
can detect the motion not being smooth but I suspect that it way below 60
FPS. In fact my gut feeling is that this is closer to 10 FPS. Think about
movies which are 24 FPS do these not seem smooth to you when you go to the
theater? In addition I believe that the current HDTV standard calls for 30
FPS. I think if it required more than this frame rate to get a smooth
presentation that the standard would have a higher frame rate. One other
data point the FAA requires that certified flight simulators must have a
frame rate of at least 10 FPS. My own experience with FG is that anything
over 20 FPS feels just fine as long as the CPU is doing everything it needs
to to keep each frame synced to what should be happening. So Andreas should
be golden at 60 FPS with his LCD display.


Cquote2.png
Cquote1.png The reason to use higher refresh rates on CRTs is that this reduces the

flicker that occurs because the phosphors start to fade during the longer
interval between passes of the electron gun at slower refresh rates. LCDs
don't have this issue because the pixels have a more or less constant output
at any setting. EI. no fading during the refresh cycle like a CRT and
therefore no flicker even at very slow refresh rates.


Cquote2.png