Re: Frame buffer snapshot

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Hal Bertram (hal++at++jhcscg.dircon.co.uk)
Fri, 30 Aug 1996 13:57:19 +0100

On Aug 29, 10:43am, Andrew Ng wrote:
> Subject: Frame buffer snapshot
>
> [ plain text
> Encoded with "quoted-printable" ] :
Hi,
>
> I've implemented a frame buffer snapshot facility in our Performer 2.0 based
application, running on a Max Impact with IRIX 5.3. The problem that I'm having
is when the Performer window is covered by other windows on the desktop. When
this occurs, the snapshot taken has garbage in these areas that are covered by
other windows. It looks as though pixels have not been written into these
areas. Is there anyway that I can avoid this, without having to raise the
Performer window to the top?

As far as I am aware, those pixels are not drawn. Each pixel has a number of
info bits which tell it which window it belongs to, and only those will be
drawn by the graphics. Occasionally if a window with less pixel depth (e.g.
colourmap) overwrites and RGB, some of the image will still be there in the RGB
planes, but will certainly not be updated.

Maybe you can use an offscreen buffer to create a clear view, or if you know
that you will always have a certain area visible, render to that a number of
times and arrange the tiles back into a complete image. Or possibly ask the
window manager to raise you and lower you either side of the grab.

Hal

-- 
Hal Bertram
Jim Henson's Creature Shop
30 Oval Road, London NW1 7DE, UK


hal++at++jhcs.co.uk


Tel: +44 171 428 4000
Fax: +44 171 284 2218




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