Ray Marden wrote on Oct 8, 2011, 22:34:
Yes, with v-sync disabled, the screen refreshes as much as it can whether it'a a full or partial (tearing) update.
But enabling v-sync does not cut your framerate in half - the game simply refreshes the entire screen as often as it can.
If you have a slower computer, v-sync probably does make the overall experience more smooth, albeit with a sh*t ton of tearing. However, I would gladly take a v-sync experience equivalent to 40hz, 50hz or 58hz instead of capping the game's framerate to 30 FPS.
V-Sync doesn't work like that. It works by synchronising the framerate to the refresh rate of your monitor. Therefore if you have a 60hz monitor - like 99% of monitors out there - then you have to either sync to 60hz or 30hz, as otherwise you'll have incomplete frames. You can't pick an arbitrary figure like 40hz, as then you'd be rendering 1.33 frames for every frame the monitor displays. By dropping to 30fps you get one frame for every two cycles of the monitor, eliminating the tearing but halving the framerate. There is a technique called triple buffering that goes some way to minimising the framerate drop but I find that it makes games feel less responsive (it's an option for L4D2 if you want to try it out).
Now they've added a Smart option that basically syncs the game to 60hz whenever it can but if the performance drops it accepts a bit of tearing, much of which you probably wouldn't even notice if your framerate doesn't drop below 60fps that often.
Don't forget, when we're talking about dropping to 30hz that's only momentarily - as soon as the framerate is above 60fps it goes back to 60hz. It might only be for a fraction of a second but some people notice it more readily than others.
"The price of freedom is eternal vigilance."