Re: double buffer

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On Wed, 22 Mar 2006, Florent Monnier wrote:

> >    You can render to a pixmap and then copy the contents of the
> > pixmap to the window with XCopyArea().  This will be similar to
> > many implementations of glXSwapBuffers, however, many GL implementation
> > allow synchronization with the refresh rate, while Xlib offers no
> > such feature.  Note that glXSwapBuffers executes an implicit
> > glFlush, while XCopyArea does not execute an implicit XFlush.
>
> Thanks a lot!
>
> It works, but there is a big big loss of performence !
>
> Without double buffer the frame rate can be for a test example
>   380 frames per seconds,
> but with double-buffer it slows a lot down to
>   30 frames / seconds.


   That sounds like the pixmap didn't get put in videoram, which
is unfortunate.  It probably would have been fast if the pixmap
was in videoram.  Does this card have very much videoram?  If
you VT switch to the console and then back to X (to clear out
the existing videoram pixmaps) before starting your app does it
run significantly faster?


			Mark.

>
> Is it normal ?
> Is there tricks to improve the cost of the double-buffering ?
>
>
> --
> Thanks in advance
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