Distributed graphics: where to draw the lines?
Authors: Phillips D. , Pique M. , Moler C. , Torborg J. , Greenberg D. 
Published: November 2005

Good morning, ladies and gentlemen. Welcome to the panel
entitled Distributed Graphics: Where to Draw the Lines?
My name is Dick Phillips. I'm from Los Alamos National
Laboratory and I'll be your chair this session. I'll be joined by a
great group of panelists --- friends and colleagues all.
Our second speaker following me will be Michael Pique from
Scripps Clinic. Following him will be Cleve Moler from Ardent
Computer. After Cleve we'll hear from Jay Torborg who is associated
with Alliant Computer. And batting in the clean-up position is
going to be Don Greenberg from Cornell University.
I have to give you one administrative announcement. You probably
know this by now if you've been attending panel sessions all week.
But once again, these proceedings are being audio taped for
subsequent transcription and publication. That means that when we
open up the session for question and answer, which will be in
another 30 or 40 minutes, if you would like to ask a question, you
must come to one of the microphones that's situated in the aisles.
They are just about in every aisle, part way back and close to the
front. And to be recognized, please state your name and
affiliation, and I'll remind you of that when we get into the
question and answer session.
The title of our panel begs a question --- where to draw the
lines. Well, the trivial answer to that question is obviously on
the display that you have available. The real implication of that
title was where to draw the lines of demarcation for graphics
processing. You're going to hear from me and from my other
panelists several different points of view. Just when you thought
everything was settling down and it was clear that all graphics
processing was moving out to workstations or graphic
supercomputers, you're going to hear at least two different points
of view that may sound a bit nostalgic.
Let me take you back in time just a bit, and this is a greatly
oversimplified graphics time line --- where we have been and where
we are and where we're going in the evolution of visualization
capability.
I'm not going to dwell too much on the part of this time line to
the left. We're really interested in what's up at the right hand
side. But I can't resist pointing out that back in the days which I
have labeled pre-history here, a lot of us can remember getting
excited about seeing output in the form of a printer plot, thinking
that we were doing visualization and that that was really computer
graphics. And I for one can remember the first time I had 300 band
available to me on a storage tube terminal and I thought this is
blazing speed. I cannot believe what kind of graphics capability I
have got now.
Where things really get interesting though, if you move along
that time line to the right, up into the mid 1980s, I have put some
I think seminal events on there --- Silicon Graphics introducing
the geometry engine in the workstation. Well, workstations in
general. That was a real watershed event that has changed the way
that we do graphics and where we do graphics considerably.
Then as we move into the later part of the 1980s, I have noted
the appearance of graphics accelerators for workstations. These are
specialized plug-in boards that have all of the graphics features
like Phong shading and high speed transformations built into them.
Graphic supercomputers like Ardent and Stellar and HP/Apollo have
appeared in that time frame. Then we look a little bit further into
the '90s and I have indicated the occurrence of very high speed
networks is going to have a profound effect on the way we do
graphics display and how we distribute the activities that are
associated with it.
Let me give a very oversimplified couple of statements on what
gave rise to the need for specialized graphics hardware --- the
accelerators that I talked about and indeed the graphic
supercomputers. As I've said, to terribly oversimplify, it was
certainly the need for real time transformations and rendering. All
of the advances in computer graphics over the last 10 or 15 years,
many of them we can now find built into the hardware of the
workstations and graphic supercomputers that we have available to
us.
One of the other reasons for wanting to bring all of that high
speed computational capability right to the desktop, as it is, was
to compensate for the lamentably low communication bandwidths which
we had then --- which we have now, as a matter of fact. And I'm
even including Ethernet and I'll be bold enough to say that the
FDDI, which is not really upon us, is also in that lamentably slow
category for many of the kinds of things we'd like to do.
It turns out --- in my view, at least --- that that specialized
hardware, wonderful as it is for many, many applications, and make
no mistake, it has revolutionized the way that we can do
interactive graphics --- it's not useful for all applications.
One application that I've listed as a first bullet is one where
we're doing specialized rendering --- research rendering let's call
it. Not everything we wanted --- not all the research in rendering
has been done --- right? So Gouraud shading and Phong shading and
so on is not the be-all end-all necessarily. There's a lot of
interesting work being done. It has been reported at this
conference, as a matter of fact.
That is really a small reason for wanting to do the graphics
computing on yet another system. But the next one that I've listed
is a very compelling reason in many installations, particularly
where large scale heavy-duty simulations are being done. I've
mentioned that I'm from Los Alamos and that's certainly one center
where there are computations that are done on supercomputers and
that need to be visualized, and because of the nature of the
computations all of the specialized hardware in accelerator boards
and in graphic supercomputers is not necessarily useful. Indeed,
I'll argue that in many cases it's of no value whatsoever.
The last point I want to make here --- before I show you a
couple of specific slides of these simulations that I'm referring
to --- is that what will happen is that the emergence of very high
speed networks --- both local networks and international and
national networks --- is going to provide a way for these large
scale simulations to take advantage of graphics hardware that does
not necessarily have the specialized capabilities we just talked
about.
At Los Alamos a group of folks in our network engineering
department have taken the lead in defining what is called the High
Speed Channel specification. Before I get to that, let me just give
you an idea of the kinds of computations that are being done at Los
Alamos --- and I know at many other places --- that simply can't
take advantage of the specialized hardware that I've just been
referring to. This happens to be the mesh that's associated with a
finite difference computation for some simulation. It doesn't
really matter what it is, but I just wanted to show you that we're
talking typically tens of thousands of individual mesh points, and
I can guarantee you this is a fairly sparse mesh compared to the
kinds of things that most of our users encounter.
The point in showing you this is that as the simulation evolves
in time, there is a different version of this mesh for every single
time step. The scientists who are doing the simulation would like
to be able --- either after the fact or perhaps if the timing is
appropriate --- to steer the computations that are going on by
being able to visualize the evolution in time of meshes like this.
And they need to be sent to some display device. And ideally you'd
like to do that at the rate of 24 frames per second, but we can go
through some computations and find that's simply not feasible with
the kind of network bandwidths that are available today.
The specialized hardware that I've just been talking about gives
us no help at all here, because what I need to be able to do is to
send one instance of this mesh to the display device for every time
step, as I mentioned a moment ago.
In addition, the scientists at Los Alamos and other places would
like to be able to have the counterpart of a numerical laboratory.
This is completely synthesized, but you can --- and many of you may
have had experience in the past with visualization techniques and
fluid flow, where you can actually see shock waves by various
lighting techniques. The intent here is to be able to simulate that
situation and be able to show the flow evolving --- not necessarily
as it's being computed, but perhaps after the fact --- but be able
to pick out important points by seeing a temporal evolution of that
particular simulation.
So those are just a couple of examples that have given rise to
the development of a high speed channel specification and an
accompanying network at Los Alamos, and I wanted to say right now
--- just so you don't think oh, great, a special purpose solution
for a national laboratory that no one else will ever be able to use
--- not so.
Many of you out there I am sure know --- and I know several of
our panelists are either aware of or working on high speed channel
hardware for their particular products. There are about 30 vendors
that have signed on to the high speed channel specification.
In addition, Digital Equipment Corporation is building the
corresponding network, which is called CP*. I'm not going to go
into network details here because that's not my point. I really
wanted to describe what is now a new highway for data transmission
that facilitates my job, which is to help the scientists do the
visualization that they need to do.
So what we're seeing here is a very simplified view of how this
high speed network, which is spec'ed at 800 megabits and a
corresponding cross bar switch-style network that is going to allow
effective point-to-point connections between the various components
of the computing environment --- the supercomputers, the data
storage devices, and the display devices. And each --- unlike with
a bus structure --- each user will effectively have that complete
bandwidth available to him or her.
A larger view of that network is shown here and it gives us an
idea of how we might interconnect the various devices and again. I
don't want to go through the details here, but you notice that
we're accommodating FDDI gateways, so that the FDDI LANs can be
used easily in this environment, and various workstations. I've
shown a Sun workstation there. I described vendors who are signing
on to this concept, and Sun is providing a high speed interface to
their TAAC board, which can then be put into a Sun workstation, and
connected at 800 megabits directly over the network.
I mentioned earlier that this is not necessarily limited to just
our local area networks. Many of you are probably aware of the work
that's going on now to establish these so-called national data
highways. The Corporation for National Research Initiatives is
coordinating an activity to establish centers throughout the United
States that will participate in a test bed of what is to become in
the 1990s a four gigabit data highway spanning the United
States.
So I'd like to leave you with the thought that while we have
migrated a lot of the graphics computing capabilities --- graphics
related computing requirements to workstations and specialized
graphic supercomputers --- the emergence of extremely high speed
data communications makes one rethink these situations ---
particularly when you are faced with the kinds of computing tasks
that I just mentioned that we have for large scale simulations at
national laboratories.
I'm going to stop my heretical remarks here and I'm going to
turn it over to the panel to describe several different points of
view.
As I mentioned earlier, the next speaker will be Michael Pique
from Scripps Clinic and Research Foundation. Michael? Thank
you.