annala@neuro.usc.edu (A J Annala) (01/05/91)
I have not used the LBL SCRY package extensively. It is much smaller in size
than any of the other source code available systems described previously. It
installed quite easily on my SUN system. As described below, SCRY provides an
excellent example of how to perform compute intensive tasks on supercomputers,
display intermediate results at a workstation, and use an ibm pc to operate a
stand alone insert edit frame by frame animation controller for making movies
of computational fluid dynamics (and other) simulations. I cannot recommmend
this system positively or negatively -- however, if you are interested in the
generation of video movies on a $10,000 or less investment then you may learn
much from examining this system.
Alexander-James Annala
Neural, Informational & Behavioral Sciences Program
HEDCO Neuroscience Building, Room 534
University of Southern California
Los Angeles, CA 90089-2520
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The following is reprinted from the scry software distribution literature:
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Scry is a distributed image handling system that pro-
vides both image compression and transport on local and wide
area networks, and a collection of higher level graphics and
scientific visualization functions. The system can be dis-
tributed among workstations, between supercomputers and
workstations, and between supercomputers, workstations and
video animation controllers. The system is most commonly
used to produce video based movie displays of time dependent
data and complex 3D data sets, and to handle the images
resulting from certain image processing operations.
In the scientific visualization process, the system is
typically used in one of two configurations. In the first,
the supercomputer application generates data (e.g. flow
field vectors) that are compressed and sent to a graphics
workstation over a wide area network. The graphics worksta-
tion environment is used to design and debug the graphics
visualization for a movie. Finally, the raster images that
represent the frames of the movie are compressed and sent
over a local area network to the video animation controller.
Alternatively, the data, and even its representation in
terms of graphics primitives, may be too voluminous to rea-
sonably transport across a network. In this case the visu-
alization, rendering and image compression are all done on
the supercomputer. The compressed images are then sent
over a wide area or local area network to a user workstation
at the local site.
The image servers, that is the local systems that
receive the image, can be either a window based workstation,
such as a Sun color workstation using SunView, or a PC based
animation controller. All of the image servers present the
same interface to the client programs. A typical use of the
Sun based server, for example, is to have a graphics window
which displays the images as they come in from the remote
supercomputer, while storing the compressed form of the
image on disk for later video recording or preview. In the
case of the PC server the images are recorded in video for-
mat, either on tape or video-optical disk.
Layered on top of the raster image interface are
several visualization algorithms that are of general
interest. One of these is is Lorensen's Marching Cubes
[SIGGRAPH, 1987]. This algorithm provide a mechanism for
displaying the level surfaces of a 3D scalar field of arbi-
trary complexity. We have used this to explore mathematical
functions by displaying a sequence of surfaces
f(x,y,z)=c1,c2,c3 . . . . as a movie, as well as showing a
single level surface evolving in time for applications such
as flame-front propagation studies. The user interface to
this algorithm entails specification of a 3D grid of func-
tion values, the function value to be displayed, and the
presentation details of color, light source position, view-
ing position, etc.
The system has been used to make a number of movies for
Lawrence Berkeley Laboratory scientists. Scry led directly
to new insights from scientific data because of the ease
with which the system generates movies due to a simple
software interface, the ubiquitous availability of video
technology, and to the rapid turnaround between generating
and viewing movie ``clips''.
References:
W. E. Johnston, D. E. Hall, J. Huang, M. Rible, and D.
Robertson. ``Distributed Scientific Video Movie-Making''.
Proceedings of the Supercomputing Conference 1988 (The Com-
puter Society of the IEEE). Also available as LBL-24996,
University of California, Lawrence Berkeley Laboratory,
Berkeley, CA (1988).
William E. Lorensen and Harvey E. Cline. Marching Cubes: A
High Resolution 3D Surface Construction Algorithm 4 (July
1987), 163-169.
Additional references can be found in the man pages.
Note on this Distribution:
This distribution consists of the source code and docu-
mentation needed to build both the Scry servers and clients.
The development of Scry is supported by the U.S. Department
of Energy, Energy Research Division, under contract DE-
AC03-76SF00098.
This is the first revision of the original Scry distri-
bution. It now runs under UNICOS on Cray's (as well as
under UNIX on Sun's and Vaxen), with exceptions noted in the
man pages. The main additions are an implementation of
Lorensen and Cline's marching cube algorithm (for reference
see above), the capability for 3D viewing, and an expanded
Anima. There has been little change to the original
material except for Anima.
Scry is available by anonymous ftp (login:
``anonymous'', password: ``guest'') from csam.lbl.gov
(128.3.254.6) in pub/scry.tar.Z (a compressed tar file, so
don't forget to set binary mode in ftp). Be aware that the
compressed file is just over 1 megabyte. Once on your
machine, run uncompress on scry.tar.Z, and extract the files
using
tar xvf scry.tar scry
We invite your comments and suggestions about this
code. For further information contact:
Bill Johnston, (wejohnston@lbl.gov, ...ucbvax!lbl-csam.arpa!johnston)
or
David Robertson (dwrobertson@lbl.gov, ...ucbvax!lbl-csam.arpa!davidr)
Advanced Development Group
MS 50B/3238
Lawrence Berkeley Laboratory
1 Cyclotron Road
Berkeley, CA 94720