Timing problem

You're probably experiencing tearing since the program draws new frames faster than the video beam travels. So whenever they cross the screen displays two partial frames simultaneously.

hmmm i see, so how can i fix this problem ?

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Original post by LorenSoth hmmm i see, so how can i fix this problem ?

Ehm, turn vsync back on? And maybe bump up your refresh rate too.
It's main purpose is to prevent tearing (well, decent implementations also conserve CPU usage).
Attempting to refresh the screen faster than it can display new images is mostly a pointless excercise anyway.

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Original post by doynax Quote: Original post by LorenSoth hmmm i see, so how can i fix this problem ? Ehm, turn vsync back on? It's main purpose is to prevent tearing (well, decent implementations also conserve CPU usage).

But this is not the case, this is not that i want !

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Original post by LorenSoth But this is not the case, this is not that i want !

Then what do you want?
It's physically impossible to get new images to the screen any faster than the monitor's refresh rate. So short of increasing that I really don't see anything you can do about it.

Never force a refresh rate other than the default though sice many monitors/drivers report the availability of unsupported ones. So either prompt the user with a dialog in a "safe" mode or let the user set a decent default themselves.

but cant it be programmed if i know the monitors refresh rate ?

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Original post by LorenSoth but cant it be programmed if i know the monitors refresh rate ?

How to programatically set the refresh rate depends on what windowing library you're using. Since OpenGL doesn't actually specify how to set a display mode. It is generally possible though, so try looking for parameters with default values (0 is a likely suspect) in the function that set your fullscreen mode.
There's also many utilities around which can tweaking such settings manually. My NVIDIA driver came with one for example (try flipping trough the advanced propery pages of your display settings).

Unfortunately most LCDs and some (ancient) CRTs use fixed framerates.

but i think i did as you say by programatically i force to enable the vertical sync by opengl's extension EXT_swap_control ... Thanks for the support !

by the way i m using win32 and i can change it easily by the function ChangeDisplaySettings ...