Trina Roy (trina++at++bugs.asd.sgi.com)
Wed, 29 Jan 1997 15:49:24 -0800 (PST)
The Onyx2 Reality should be sufficient to run an ImmersaDesk. I dont want
to say that it does absolutely for sure unless I could test it myself
(which could happen in a month or so if need be), but the I-Desk can run
off an RE and an Impact as well so the Onyx2 Reality should be fine. Keep
in mind though the impact that it will have on the applications running
on the I-Desk. Having an application work on the I-Desk is one thing,
having it run fast enough and accurately enough visually to sustain the
frame rate needed to maintain immersion (at least 10 Hz) is an entirely
different story (remember you're rendering each frame twice, once per eye
for stereo). Without knowing more details about what you'll be running
it's hard for me to make that call. But it sounds like you have the right
information about the differences between the two systems so you can make
a pretty educated judgement call.
Good luck!!
-Trina
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
trina m. roy trina++at++sgi.com
scientific visualization silicon graphics inc.
415.933.6395 mountain view, ca
On Tue, 28 Jan 1997, Brian Corrie wrote:
>
> G'day all,
>
> I have what may seem like a silly question, but I am a bit of a newbie to high
> end SGI graphics systems and this seems like the place to clarify some things.
> Sorry about the length of this email, but I thought it best to give as much
> info as possible to avoid confusion. We are looking at purchasing an
> Immersadesk VR system and an Onyx2 Reality Deskside system to drive it. The
> Immersadesk is a drafting sized immersive VR system with stereo viewing and
> both head and hand tracking. Up until recently, these devices were typically
> driven by a Onyx RE or Onyx IR system, usually with 1 pipe. Given the
> previous statement, it appears obvious that the Onyx2 Reality Deskside system
> would be more than capable of driving the Immersadesk.
>
> The problem (and my question) arises from the fact that the Onyx2 Reality is a
> scaled down version of the Onyx2 IR and I am not familiar enough with high end
> SGI hardware (nor familiar enough with the VR requirements imposed on these
> machines) to determine whether or not this 'scaling down' is going to impact
> drastically on opearting the Immersadesk... I am unfortunately in the
> position that I have to advise the powers that be on whether the machine will
> be capable of driving the Immeradesk successfully, so I need to find these
> things out...
>
> The main potential problem is the configuartion of the frame buffer. The
> Onyx2 Reality has an RM8 with 40 MB of frame buffer as standard, which is half
> the frame buffer of what the IR RM7s have (80 MB). To drive the Immersadesk,
> we require 1280x1024 stereo, double buffered rendering. With 40 MB of frame
> buffer at 1280x1024 pixels, this gives us 256 bits/pixel. My problem is that
> I do not know enough about the frame buffer modes of the IR pipes to be sure
> that we are not going to lose some capabability that we require due to having
> "only" 256 bits/pixel. If we are using 12bit RGBA pixels with stereo double
> buffering my calculations tell me that we need 4 x 48 bits (for left/front,
> right/front, left/back, and right/back images) and we will say 23 bits for
> depth. This leaves us with just over 40 bits/pxel remaining, which seems like
> more than enough...
>
> So my question is, am I missing anything here???? Our SGI reps here in
> Canberra have expressed some concern that this may not be enough.
> Specifically, they have stated that there will be no anti-aliasing available
> (only 1 sample per pixel). I have the Onyx2 Technical Report and it mentions
> the Accumulation Buffer, stencils, overlays, tags, and things like LA32, LA16,
> and MS Color (see page 20 of the Onyx2 Tech Report) without really defining
> what they are and how they are used. What I need to know in what
> circumstances are they used and how many of my valuable bits/pixel are they
> going to chew up? I am also interested in finding out if any of these are
> essential in driving a system like the Immersadesk and if so, will my 40 MB of
> frame buffer be enough... (Gee, I am really starting to sound possesive about
> that good ol' Onyx2 Reality box, I wonder if they will let me have it in my
> office 8-)
>
> I am hoping that someone on this list is both an Onyx2 and an Immersadesk
> user, as that is really what I need to answer my questions. Of course any
> input from anyone would be HUGELY appreciated!!!!
>
> Thanks in advance,
>
> Brian Corrie.
>
>
>
>
>
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
trina m. roy trina++at++sgi.com
scientific visualization silicon graphics inc.
415.933.6395 mountain view, ca
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