Refresh Rate - FPS - Vsync etc

[LeeBe]

Hi, just a quick question about these few things.

I've seen a lot of posts on the net, a lot of them here, but a few things I cant quite work out, some seem contradictory, so I thought I'd ask the experts.

1) If your card is rendering 3 frames in the time it takes your monitor to show 1 frame what happens to the other two? are they all shown? or do you lose the first two?

2) vsync locks frames to the refresh rate of your monitor, on a LCD its about 60, though refresh doesnt matter on LCD (? another Q?) so is there any way to lock it to the pixel response time? I have an 8ms panel, shouldnt that be around 125hz? (1000/8)

3) In a fast FPS game (I play UT99 a lot) would it be best to render as many frames as I can (300+ fps) even though I've got an lcd that cant display anywhere near that number.

im sure theres more but thats all I can think of just now.

oh and if anyone has some links to info about this post them please.

 

[Bolloxoid]

1) If your card is rendering 3 frames in the time it takes your monitor to show 1 frame what happens to the other two? are they all shown? or do you lose the first two?

The frame drawn by the monitor will be a combination of the three frames output by the adapter, i.e. there will be discontinuities along the vertical dimension.

2) vsync locks frames to the refresh rate of your monitor, on a LCD its about 60, though refresh doesnt matter on LCD (? another Q?)

Refresh rate still does matter with an LCD, it determines the maximum frame rate you can see displayed. Not that there is much choice, most LCDs can accept 60 or 75 Hz max.

3) In a fast FPS game (I play UT99 a lot) would it be best to render as many frames as I can (300+ fps) even though I've got an lcd that cant display anywhere near that number.

Do what suits you the best. Rendering at higher frame rates can improve the responsiveness of the game even though you can never see more (whole) frames than your refresh rate.

 

[Arwin]

Do what suits you the best. Rendering at higher frame rates can improve the responsiveness of the game even though you can never see more (whole) frames than your refresh rate.

I think that there are two possibilities.

- games that have the amount of physics, AI and other kinds of calculation somehow linked to the framerate (i.e. perform a certain calculation every x frames) will benefit

- games that have a separate render engine that just goes as fast as you allow it, will not necessarily benefit

 

[Blazkowicz]

Refresh rate still does matter with an LCD, it determines the maximum frame rate you can see displayed. Not that there is much choice, most LCDs can accept 60 or 75 Hz max.

and higher res LCD can only do 60Hz. that sucks, being limited to 60fps in an old, fast paced multiplayer game like UT99, quake 3 or CS is bad.
tearing (with Vsync off) is also a bigger problem the lower your refresh rate is.

 

[LeeBe]

Thanks for the replies, I'm still a bit unsure about this one.

Refresh rate still does matter with an LCD, it determines the maximum frame rate you can see displayed. Not that there is much choice, most LCDs can accept 60 or 75 Hz max.

when I was buying a LCD I was told that refresh rate wasnt important anymore, it was the response time that was important.

Would the refresh rate on an LCD still have any effect if vsync was off?

 

[Bolloxoid]

when I was buying a LCD I was told that refresh rate wasnt important anymore, it was the response time that was important.

Well, it isn't quite that simple. With an LCD, your displayed (not necessarily rendered) frame rate is capped at 60 to 75 fps, while with a CRT you can achieve 85 to 100 fps.

Would the refresh rate on an LCD still have any effect if vsync was off?

Yes. There will be more tearing at lower refresh rates.

 

[Dio]

Whatever the hardcore FPS people say, more than 60fps is pretty useless to the eye. With higher rates, latency does drop a touch, but since human reaction time is 100ms at best the difference between 16ms and 10ms is unlikely to give anyone any trouble.

However, if the hardware can't sustain 60fps continuously, the occasional 30fps frame is far more noticeable than an occasional 50fps frame, and if the render load increases enough to drive the rendering very near to the boundary the artifact can be quite unpleasant.

 

[KimB]

But fortunately if you make use of triple buffering, there's no need to worry about integer drops in framerate: the hardware doesn't sit around waiting for the next frame update, it can keep working.

Anyway, yes, I claim that response time is going to be more important for games than refresh rate on LCD's. This is simply because few LCD's today have a response time that is actually as good as the refresh rate they support. So there wouldn't be much point in displaying a higher refresh rate if the pixels can't update that fast.

 

[ShootMyMonkey]

Whatever the hardcore FPS people say, more than 60fps is pretty useless to the eye. With higher rates, latency does drop a touch, but since human reaction time is 100ms at best the difference between 16ms and 10ms is unlikely to give anyone any trouble.

Human reaction time is different from human eye latency and the ability of the brain to continue taking in information, so things can still look smoother because there is more information about movement as the framerate gets higher. How useful it is is certainly a valid point, but most user input processing happens at a very different rate than sampling every frame. Otherwise, we'd probably end up capturing a lot of noise simply because a gamer's hand is not exactly as stable as a surgeon's hand.