[gl4java-usergroup] Re : fill rate limit/benchmark

[Alban C. <aco...@wa...>]

>Hi,

> I'm just guessing here, but when you do the opengl swapbuffers command,
> I'm pretty sure it has to wait for the next vertical refresh on your
> monitor before it happens.  So your swaps are quantized to 85hz,
> or whatever your monitor is set to.

> If you increase the resolution so that it can no longer run at
> that speed, suddenly it should jump to half that speed.

Thanks for the tip noisebrain :)
This is an important issue for fullscreen mode.

I think this paragraph from a Power VR whitepaper explains why :

Frame Rate Limiting/Locking
Most games today allow the frame rate to seek it's own level and to go up
and down as the scene complexity changes.  This looks ok when you're running
at less than 30 frames per second but if your game occasionally bounces
between 30 and 60 frames per second (or even 30 and 120!) the speed changes
start to get pretty jarring since your talking about frequent
doubling/halving of speed.  The higher your average frame rate is, the more
necessary it is to keep the frame rate constant for things to look smooth.
For this reason, most games will want to throttle their performance and lock
in on a frame rate that they can maintain fairly consistently.  There are a
lot of ways to do this which I won't go into here, the main thing you want
to be sure of is that you pick the RIGHT number to lock in on.  You need to
determine the refresh rate of the monitor and pick a frame rate that is a
multiple of that monitor's refresh rate.  If, for example, you try to lock
in at a 30hz frame rate when the monitor is running at 75hz, your frame rate
will tend to wobble between 37.5 and 25hz.  The overall effect is not
immediately obvious (usually the game still feels "fast" but not "smooth")
but over time it can cause considerable eyestrain and fatigue in the player.
In addition to locking in at a multiple of the monitor refresh frequency, it
's also a good idea to run the monitor at the highest refresh rate it can
manage as it gives you more potential "notches" you can lock into. At 60hz
you only get four choices from max speed down to 15 hz (60, 30, 20 and 15)
At 120 hz you get 8 (120, 60, 40, 30, 24, 20, 17, and 15) which gives you
more chances to pick your highest speed, and makes the change less
noticeable if your engine accidentally skips a frame.

Regards,

Alban