need front and back buffers to have same image

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Madhu Sethi (madhu++at++cae.ca)
Fri, 28 Jun 1996 10:08:07 -0400


Hi,

I need to have both the front and back buffers of a channel contain the same
scene instance, while my program is continuously updating this scene, therefore
drawing a new iteration into the backbuffer which is continuously swapped.

What I've tried:

channelDrawCallback(..) {

/*
by default, the backbuffer is enabled for writing, while the front buffer is
being displayed. I want the same scene written to both buffers, so I enable the
front for writing.
*/
        frontbuffer(TRUE)
        chan->clear()
        pfDraw()
        frontbuffer(FALSE)
}

The problem is that while the frontbuffer is being displayed, it is being
cleared(?) and overwritten, and this glitch is visible. Is there anyother way
 - any routine that will directly copy front buffer to back (or vice versa)
without using the system bus? And when is a good time to do this so that any
side effects will not be seen? BTW, this is in display-list mode - I'm
multiprocessing the cull and draw.

Thanks for any ideas...

-- 
Madhu Sethi			CAE Electronics Ltd., 8585 Cote De Liesse
Software Developer		Saint-Laurent, Quebec, Canada, H4L-4X4
3-D Graphics Applications	tel: +1 514 341 2000 extension 2275
madhu++at++cae.ca			fax: +1 514 340 5496
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