Archived

This topic is now archived and is closed to further replies.

josemarin

VSync : why?

Recommended Posts

Vsync makes things look smoother. The reason is a little complex, but it has to do with how your monitor functions:

Your monitor has what''s called a refresh rate. This is how many times per second whatever is on the screen is drawn. It''s independent of the framerate of any application, and it''s generally between 60 and 75 Hz (Hz = cycles per second). Each cycle of your monitor, the photon gun that creates images reaches the bottom right corner of your screen and resets to the upper left. During this time, a vertical synchronization (vsync) signal is set. If you have vsync enabled, what happens at this time is that the image information for the screen (i.e. everything you''ve drawn) is sent at the exact moment the photon gun is reset, so that it draws all your information in one pass. If vsync is disabled, information is uploaded at any time during the photon sweep, meaning 1/2 or 3/4 of your image may not be updated ''til the next frame, so you get part of one frame and part of the next on the screen at once. This causes "tearing," which is much faster as you''ve noted, but it''s also less visually attractive.

Peace,
ZE.

//email me.//zealouselixir software.//msdn.//n00biez.//
miscellaneous links

Share this post


Link to post
Share on other sites
An unfortunate side effect though is that having VSync enabled is that its either all or half. For example, your montior can run at 85 Hz at 1024x768, which is 85 fps. If your video card is not able to render the scene at 85 fps, it has to cut your FPS in HALF, which would leave you with around 42.5 fps( I''m guessing this is because it has to wait on the NEXT Sync signal from the monitor) . If you can''t render that, it drops it down yet again, to around 21 fps. In some games this may be acceptable, but in first person shooters it isn''t.

Share this post


Link to post
Share on other sites