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Don't wait for vsync

Posted on 2003-11-18
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Last Modified: 2013-12-06
How do you turn off the "wait for vsync" in OpenGL? I feel so silly asking such a simple question, but I can't find the answer anywhere (and believe me, I've looked). I'm using SDL as well, so if there's an SDL wrapper, I'm down with that!

Thanks!
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Question by:arudson
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9 Comments
 
LVL 45

Expert Comment

by:sunnycoder
ID: 9778585
There is no Vsync in OpenGL as a command. Most apps use the GLFlush command, sometimes followed by a GLFinish command.
http://www.d-silence.com/video/vsync2.shtml
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Author Comment

by:arudson
ID: 9780120
Actually, I managed to find some information on page flipping controls. It turns out there's a (win32?) extension that will control the frequency of the page flips: WGL_EXT_swap_control

The associated functions are:

bool wglSwapIntervalEXT(int)  // sets the update frequency (0 means no VSYNC)
int wglGetSwapIntervalEXT(void) // gets the update frequency

The frequency is in terms of vertical retraces. So if you say wglSwapIntervalEXT(2), OpenGL will wait for 2 retraces before flipping to the backbuffer.
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LVL 45

Accepted Solution

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sunnycoder earned 500 total points
ID: 9784762
arduson,

WGL_EXT_swap_control is an OpenGL extension supported by some accelerators and driver versions. While GeForce and TNT support it, 3D labs and ATI Radeon don't. Using it will lead to largely unportable code even for windows which IMHO will not be acceptable for most(any?) real world opengl application ... The correct solution is the one listed in my first post.

If you still wish to have the question deleted, go ahead.

Sunny
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LVL 1

Expert Comment

by:Computer101
ID: 9802905
PAQed, with points refunded (500)

Computer101
E-E Admin
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Author Comment

by:arudson
ID: 9810609
Sorry Sunny. I would have given you the points, but I guess the post was closed during the weekend. I only check this board at work, during the week.

Thanks for the info, anyway.
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Author Comment

by:arudson
ID: 9817874
Yes please! Can you accept Sunnycoder's last comment?

Thank you kindly.
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