Steve Baker (sbaker++at++link.com)
Tue, 28 Jul 1998 10:04:29 -0500 (CDT)
> I'm relatively new to Performer and I have been reading the
> documentation that came with it and it wasn't clear to me if it is
> possible to use two or more Pipes to render to the same frame buffer. I
> also got the understanding (and correct me if I'm wrong) that the word
> "Pipe" is used in place of "Graphics Hardware", so another words a Pipe
> is a graphics board or "Raster manager" in the machine.
The terminology is in a bit of a mess IMHO.
PIPE: On the higher end machines like ONYX's and such, a PIPE is a physical
chunk of hardware comprising one Geometry Engine board, either 1, 2 or 4
Raster Managers, and a Display Generator. (And possibly some other
bits and pieces too). One pipe can drive several video outputs on
some hardware - there are also occasions when people have combined
multiple PIPEs to render a single video output - but you need some
special hardware to do that. Most programs are unaware of how many
video outputs are displaying the output of the pipe.
On lower-end machines like an O2, a pipe is just a graphics board.
RASTER MANAGER: A board that plugs into a PIPE. All the raster managers
installed in a particular pipe contribute pixels to the frame buffer
for that PIPE in an interleaved fashion. If you ever have a raster
manager fail (No! Surely not!) on a pipe that has more than one
raster manager, you often get a bunch of vertical lines on the
screen where those parts of the overall frame buffer that reside
on that pipe are missing.
pfPipe: A Cull process and a Draw process associated with an X-window -
there can be multiple pfPipes associated with a PIPE - but each
pfPipe renders to just one PIPE.
CHANNEL: Depending on what documents you read, this can be a
PIPE, a VIDEO OUTPUT, a pfPipe or a pfChannel - avoid this
term!
pfChannel: A rectangular portion of a pfPipe into which an image is
(usually) rendered. There can be several pfChannels associated
with a single pfPipe. There is not necessarily a direct relationship
between a pfChannel and a video output - but this is often
the case.
> ...it wasn't clear to me if it is
> possible to use two or more Pipes to render to the same frame buffer.
Two or more PIPEs ... No.
Two or more pfPipes ... Yes.
> And since each raster manager has it's own hardware frame buffer...
(Well, it's own share of the PIPE's frame buffer actually)
> I was
> wondering if it's possible to get two pipes to work together in rendering
> a scene to one window with one channel in it.
No - you can't have a 'window' (an X-window specifically) that straddles
more than one PIPE (or more than one pfPipe for that matter). There have
been cases where multiple PIPES have been used to drive a single video -
IIRC, the Disney Aladdin ride did that at one time. It needs some special
hardware though.
Steve Baker (817)619-2657 (Vox/Vox-Mail)
Raytheon Systems Inc. (817)619-4028 (Fax)
Work: SBaker++at++link.com http://www.hti.com
Home: SJBaker1++at++airmail.net http://web2.airmail.net/sjbaker1
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