Member Community

[Marek]

In VMK 1A I explain the inner workings of the vertical synchronization feature built into a computer's video card and monitor. I then show you how to disable it so that we can get the game engine running at more than the standard 60 fps.

VMK 1B/C demonstrates how to add a check box to the Options Menu that will allow you to turn vertical synchronization on and off, while the game engine is running.

[BugHunter]

Oh, the tutorial is spectacular. You certainly have a talent to explain the concepts.

Probably the only thing that also should be mentioned is a double buffering, which is a standard in 2D/3D graphics. It increases the smoothness of animation and reduces the flickering of the screen, allowing to switch vertical synchronization off with minimal detriment to user’s experience.

If somebody is interested to know more about WGL_EXT_swap_control extension, here is a link to official description:
http://www.opengl.org/registry/specs/EXT/wgl_swap_control.txt
In particular it gives more detailed explanation of the parameter to BOOL wglSwapIntervalEXT(int interval):

Quote:

The parameter <interval> specifies the minimum number of video frames that are displayed before a buffer swap will occur...

In addition to all that, it is rumored that you cannot disable V-Sync if it is prohibited in the options of video-driver.

[Groggy]

I've watched the vid. and I understand how to turn off vsync, but I'm not sure why you would want the vid. card to work harder than it has too.

Does the program stop after completing the frame and has to wait 7ms before it continues or is it just the vid. card that stops for 7ms?

If the program stops, then I can understand turning vsync off. But if it's just the vid. card waiting to display the buffer, then whats the harm in waiting? You're writing data to a buffer which no one is seeing anyways. Or have I missed something?

thanks.

[BugHunter]

When the vertical synchronization is ON the function SwapBuffers() inside the main application loop blocks the execution thread of the application. So, as you said, the program stops and waiting.
The main reasons to turn V-Sync off are:
1) estimate the top performance of the hardware/software
2) if actual application’s FPS is less than monitor’s refresh rate it may in some circumstances increase the apps performance.

[Groggy]

Thanks, was wondering about #2 also