Re: help -- timing problem

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From: Angus Dorbie (dorbie++at++sgi.com)
Date: 01/11/2000 13:30:23

Issue a glColor call after tha swap call, this will cause you to block
until the swap has completed.

CHeers,Angus.

Fangtu Qiu wrote:
>
> Hi,
>
> I need to know the exact time when the graphics card swaps the buffers by
> following method:
>
> glXSwapBuffers
> glXWaitVideoSyncSGI
>
> The glXSwapBuffers only issues the command to swap the buffers and returns
> immediately before the buffers are actually swapped. The command will be
> completed during the next vertical retrace. So, after glXSwapBuffers
> returns, the program calls glXWaitVideoSyncSGI to determine the vertical
> retrace.
>
> Now the problem is that when the glXSwapBuffers returns, sometimes the
> vertical retrace occurs, the graphics card swaps the buffers before the
> program calls glXWaitVideoSyncSGI. Therefore the returning time of
> glXWaitVideoSyncSGI will be one frame later then the actual swapping time
> of the buffers.
>
> Any good method to resolve the problem? Is there any method to access the
> codes that determine the actual swapping of the buffers?
>
> Thanks.
>
> Fangtu
>
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