V SYNC

[eastley]

I have been playing Colin McCrae Rally 3 lately and when I put V SYNC on application control it jerks alot, but when I turn it off the game wont load into the stages, does anyone know why this is?

I have a MSI 5900XT-VTD by the way. I'm using the MSI NVIDIA 56.63 Drivers form there site.

 

[Bucksnort]

v sync times the monitors refresh rate to the fps displayed by the game. In other words, if your refresh rate is set to 85hz then the maximum fps you can get in a game is 85 fps. Many keep v sync set to always off in the video display properties control panel to get the maximum fps your video card can deliver. Sometimes turning off v sync will produce a tearing visual effect but I have never had this problem. Try setting v sync to always off in the direct 3d settings of your nvidia control panel. Make sure you use a decent refresh rate for your monitor, 85-100.

 

[eastley]

Thanks for that, anyway I have tried several things even driver changes and I stil get this jerk, its like getting lag from, playing on the net or a network. Any other suggestions?

 

[Avalon]

I have a pretty lousy 17" HP monitor that can only do 85hz at a max res of 10x7. I noticed in older games, such as halflife based games where I easily get more than 100fps steady, that my games were slightly jerky at times. I turned on vsynch, and now those games play smooth as butter. I think it was tearing that gave me the jerky effect. I never had the problem in Farcry, but I don't think I ever hit 85fps in that game, so it was never a problem. I'm actually starting to wonder why people leave vsynch off. What's the point in getting more than 85-100fps?

 

[Pete]

A quick and perhaps incomplete explanation:

Vsync limits you to a framerate equal to or a multiple of your refresh rate. If your vsync is set to 85Hz, your screen can only be updated 85 times per second, or 42.5, or 21.25, .... Disabling vsync allows your monitor to display frames as fast as your card can render them. The disadvantage is that you may see some "tearing" of the on-screen image if the video card supplies a new frame before the monitor finishes reading and displaying the previous one from the video card's memory, so you end up with frame A on the top half of the screen, and frame B on the bottom half. AFAIK, current video cards are double-buffered: the back buffer is where the video card creates the current frame, and the front buffer is where a completed back buffer frame is flipped. The monitor gets its image from the front buffer. I believe vsync prevents the front buffer from being written to unless a complete frame can be transmitted at the designated refresh rate interval, potentially leading to the monitor displaying the same frame for multiple screen refreshes, but avoiding the problem of multiple rendered frames being displayed in a single screen redraw.

Vsync is desirable from an image quality point of view, but not from a smooth frame rate point of view. The solution is triple buffering, which takes up more memory but adds an extra (front) buffer for a vsync'ed monitor to draw from if the video card hasn't rendered a new frame in time for a new screen redraw, thus eliminating the multiple-of-refresh-rate-framerate problem.

Edit: Vsync shouldn't affect how a level loads, AFAIK.