Contents

AVS Network News Update

An Interactive Design Tool for the
Magnetic Head Bearing Slider

User Group Update

SIGGRAPH '92

WAIS and AVS

AVS '92 - A Review

Obtaining Modules

International AVS Center Module Highlights

What's New?

Development of a VHF/UHF Broadcasting
Planning and Visualization System on the Basis
of AVS

Animating Time Dependent 3D Data Using AVS

Module Submission Criteria

The AVS to Video Connection

AVS Network News

The International AVS Center serves as a catylyst for expanding the AVS 
user base.  It increases the productivity of users by fostering discipline-
specific module development and new uses for AVS.  Located at the 
North Carolina Supercomputing Center, the worldwide clearinghouse 
collects, ports, and distributes user-contributed, public domain modules 
and acts as liaison between users and vendors.AVS Network News is the 
Center's quarterly magazine and newsletter serving users and vendors 
with updates on AVS programs and their use, user's articles, editorial 
viewpoints,  and product information postings from vendors and 
independent software developers.   For an annual subscription, send a $12 
check or money order (plus $10 if out of USA),  payable to the 
International AVS Center, to the address shown below.

David Bennett, IAC Project Director, avs@ncsc.org
Terry Myerson, AVS Specialist, avs@ncsc.org
Steve Thorpe, AVS Specialist, avs@ncsc.org

For more information

The International AVS Center
Post Office Box 12889
3021 Cornwallis Road
Research Triangle Park, NC 27709-2889
Phone 919-248-1100
FAX   919-248-1101
avs@ncsc.org
 AVS Network News Update

There are several changes being made to the AVS Network News.   A 
newletter  version with two colors and in standard newletter format will 
be distributed to  AVS Users and the AVS Vendors for distribution in the 
field three times per  year.  A high end glossy will be distributed to the 
AVS Vendors only once a year  in conjunction with the AVS Conference.  
The cost of distributing the high end  glossy to 5 or 10 thousand 
individuals was prohibitive at this stage of  development.  As soon as the 
user base is sufficiently large and advertising is a  viable option, we will 
resume our current method of sending out the high end  glossy to 
everyone each quarter.  Future contributers of articles will need to 
 submit both color and black and white slides with their articles.  This 
method will  allow the AVS Vendors to purchase larger quantities and 
make the newsletter  available to many more users each quarter as well as 
allowing us to provide this  service to our AVS users. 

An Interactive Design Tool for the Magnetic Head Bearing 
BunUichiro Fujii
SONY Research Center, Yokohama, Japan
 In this paper, a network is introduced which realizes the interactive 
design  environment of the magnetic head air bearing slider in hard disk 
drive systems.   The network includes all the processes of numerical 
design:  pre-processing,  solving, and post processing.  The pre-
processing module generates dimensions  of a design target which is 
determined by dials (or other operating apparati  available in the AVS 
GUI) operated by the user.  These dimensions are sent to  the solving 
module, where calculations are expected by a calculation toggle on  the 
module.  After the calculation, results are automatically sent to the post 
 processing modules in the steady state simulations.  For transient 
simulations,  results are output to files for later animation.  Using this 
network, we can see results immediately after model modifications, 
 without any file translation or system changes.  This environment makes 
such  modification-after-modification operations quick and easy.

Introduction

Recording density of a hard disk drive system largely depends upon 
flying height  of the magnetic head air bearing slider.  A decrease of 
flying height increases the  density.  However, it also increases the 
possibility of the head crashing against  the recording disk.  To maintain 
reliability, we need to analyze the flying  characteristics of the head 
slider.

We can predict the characteristics numerically with the compressible 
viscous air  flow equation.  In our system, it cal be solved by three 
different methods:  a finite  element method (FEM), a finite difference 
method (FDM), and a Divergence- Formulation method.  The 
divergence-Formulation method is a kind of control- volume method 
which constructs equations considering the continuity of flow in  each 
small cell.

Interactive Design AVS-Network

To realize an interactive environment on AVS, a network which 
possesses all of 
the processes needed in our numerical design is developed.

Pre-Processing module

Typical dimensions of a head slider are shown in Figure 1.  Ten 
parameters can 
be selected in this version.  Each value is set with dials or other apparati 
available  in the AVS GUI.  Figure 2 show apparati used in the  network.  
These parameters  are sent to lower modules as field data.

Solving module

This module calculates:  the flying form in steady state, the pressure 
distribution  on the lubricating surface, the frequency domains dynamic 
characteristics, and  the transient response motion.  When the calculations 
toggle, the module  generates the calculation grid according to the 
dimension data sent from the  upper module and starts a calculation.  We 
use the Divergence-Formulation  routine most frequently because the 
calculations load is rather light compared to  other methods.  We can 
obtain the transient response using an FDM routine ("the  factored 
implicit scheme" by J. White et al. [1] ), but it is too time consuming to 
 use interactively in our Titan 750 system.  In certain cases, some 
modules need to  be executed remotely on larger scale supercomputers.
 
Post-processing modules and results

We visualize:  the pressure distribution, the profile of the slider itself 
(according  to dimension data), the stream lines of lubricating flow, and 
the transient  animated methods.  The pressure distributions can be 
presented as a 3D color  contoured geometry (Figure 3) using the fld to 
mesh module and colored fringes  (Figure 4) using a newly developed 
module.  A slider profile module is also  developed.  It has the 
dimensions parameter as the "Required" input and the  flying form data 
(height, pitch angle, roll angle) as the "Optional" input.  This  module 
generates 3D geometries according to these data and we can see them 
 with the Render Geometry module.  Another module was developed for 
the  animated motions of the transient response.  It is a coroutine module 
which reads  the transient data file and sends it to lower modules step by 
step.  The animated  motion can be presented by connecting the output to 
the slider profile module.   The stream lines can be generated with the 
stream lines module (Figure 5).  The graph viewer is useful to analyze the 
frequency domain dynamic  characteristics (Figure 6).  It is not preferable 
that the axis is always reset at every  input.  It is always required to 
correct the axis.

Example Network

An example network is shown in Figure 7.  The dimensions are set in the 
slider  data module and sent to the flying form calculating routine (the 
slider form2  module).  At each iteration step, the flying form data is sent 
to the slider to geom  module, which shows the slider profile according to 
each data (this appears on  the screen as an animation).  After 
convergence, the steady state pressure  distribution data is written to the 
designated file, and the dummy data is sent to  the pres field module in 
order to trigger it.  The triggered pres field module  reads the file and 
sends it to modules which rewrite the pressure (fringed)  distribution.

 Conclusion

An interactive design environment is realized in AVS.  In this 
environment, we  can determine the effect that modifications have on the 
flying form and the  pressure distribution immediately on the console.  
AVS is flexible enough to  analyze the calculated results from many 
points of view.  Furthermore, we can  easily understand the transient 
motions using the animation.  In the case of  transient analysis, the 
capacity of our Titan 750 system is not enough to operate  interactively 
and we need the remote execution capabilities of the solving  module.  

References

[1]	J. A. White and A. Nigam.  A Factored Implicit Scheme for the 
Numerical Solution  of the Reynolds Equation at Very Low Spacing.  
Journal of Lubrication Technology,  102, 80, 1980.
[2]	K. Ono.  Dynamic Characteristics of Air-Lubricated Slider 
Bearing for Non-contact  Magnetic Recording.  Transactions of the 
ASME, 97-2, 250, 1975.
[3]	A. Burgdorfer.  The Influence of the Molecular Mean Free Path 
on the Performance  Hydrodynamic Gas Lubricated Bearings.  
Transactions of the ASME, 91, 94, 1959.
[4]	Stardent Computer Inc., AVS 3 Reference Manual, Vol 1, 2, 3.


 User Group Update
Stephen Franklin
President International AVS User Group

 For those of us fortunate enough attend it, AVS U92, the first annual 
International  AVS User Group Conference, held February 11-13, 1992 at 
the International  AVS Center (IAC) at the North Carolina 
Supercomputing Center (NCSC),  offered both a valuable, memorable 
experience and a challenge.  Much of the  value was in the direct contact 
with other AVS users and in joining these other  users in discussing 
shared concerns and interests with members of the AVS  Consortium and 
with the staff of the IAC.  The challenge is how to continue these 
 contacts among AVS users and these joint discussions and how to 
broaden them  to include AVS users other than just those who can attend 
the annual  conferences.

The traditional (dare one say "logical") way of meeting this challenge 
(perhaps,  better called an opportunity) is with an umbrella user group 
organization.  Now,  most AVS users are reasonably (or unreasonably) 
busy folks with about as much  need for yet another organization to 
belong to as a mouse needs another button.   And the AVS users at the 
conference were no exception.  Even though the first  User Group 
organizational meeting wasnUt scheduled until Wednesday evening,  an 
impromptu group that started with 10 and grew to almost 30 met Tuesday 
 evening.  We discussed how to foster local and special interest user 
group  activities including broadened access to the types of activities, 
interaction, and  resources the Conference provides for attendees and for 
which the IAC  coordinates.

The enthusiasm and willingness (even eagerness) for local and year-
round AVS  user interaction was so apparent that by Wednesday 
eveningUs formal  organizational meeting (attended by over half the users 
who attended the  conference), we had volunteers to organize local user 
groups in Austria, France,  Germany, the UK, and 10 areas in the US.  
The level of enthusiasm for "by-laws"  and "articles" for a legal entity 
called the "International AVS User Group" was  not nearly so high.  In 
fact, truth be told, copies of drafts of these documents were  available and 
(by overwhelming consensus) ignored in favor of the IACUs  willingness 
to take care of administrative support for the user group for the  coming 
year while a {*de facto*} board of directors (volunteers are still being 
 sought!) investigates and then carries out the initial legal formalities.  
Meanwhile,  the consensus (again, overwhelming) was to proceed with 
the activities that the  international group of AVS users present at the 
Conference considered  appropriate for an International AVS User Group 
(IAVSUG).

So what are the user group activities to be over the coming year?  In 
addition to  next yearUs International AVS User Group Conference 
(again, chiefly in the very  capable hands of David Bennett and his IAC 
cohorts at NCSC), local AVS user  meetings are probably the most 
visible and important.  To help those who  volunteered to organize such 
meetings, the IAC is making available for these  meetings, video tapes 
from AVS U92 and full-size masters (which can be copied  to produce 
overhead transparencies) for the AVS U92 presentations, workshops  and 
tutorials. The IAC will also provide "tar" tapes of its AVS archives for 
local  user groups.  In fact, such tapes were distributed at the Conference 
to local user  group organizers.  To arrange vendor support for such local 
meetings, there is an  e-mail mailing list addressing the principal AVS 
representatives of all vendors in  the AVS Consortium.  These 
representatives will put local user group organizers  in touch with local 
vendor personnel who can help arrange local support for AVS  user 
meetings.

Because AVS use is so broad and diverse, both in discipline/application 
area and  background of its users, a real challenge for any user group is to 
facilitate  contacts among those users sharing particular interests.  
Establishing special  interest group contacts and geographic area contacts 
depends on AVS users  identifying themselves and their interests to 
others.  As a way of doing this for  yourself, just obtain an 
AVS_USER_REG form from the IAC, fill it out, and  return it via 
electronic mail according to the instructions it contains.  The 
 AVS_USER_REG registration form is available a number of ways: (1) 
 anonymous ftp it from avs.ncsc.org  (128.109.178.23); (2) any electronic 
mail  sent to avsemail@ncsc.org will receive a reply containing the form; 
(3) those  who prefer using listserv can send a message with the message 
body "get  user_grps AVS_USER_REG" (without the quotes) to 
listserv@avsusers.ncsc.org  and receive the form by return electronic 
mail.

The information and preferences you provide on the form provide an easy 
way of  adding yourself to electronic mailing lists based on your 
geographic area and  your areas of special interest.  These are standard 
listserv mailing lists to ensure  individuals the widest range of access and 
control over the mail they receive.   (Send a message with "help" as the 
message body to listserv@avsusers.ncsc.org  for more information on 
listserv.) 

There are two final items to cover in closing this article.  The first is to 
thank  David Bennett, Jeff Huskamp, Ray Idaszak, Terry Myerson, Todd 
Seemann,  Steve Thorpe, and everyone else at NCSC for their 
enthusiastic, professional, and  open support.  The second item is to 
encourage you to write to me (either at my  IAVSUG organizational 
address, iug_pres@avsusers.ncsc.org, or my personal  one, 
franklin@uci.edu) with any ideas, comments, reactions, or suggestions 
you  have about the IAVSUG.  One of the great strengths of AVS is the 
common  ground it provides for a broad, diverse range of both uses and 
users.
 
SIGGRAPH U92

A proposal has been submitted and accepted for an exhibit at 
SIGGRAPH '92.   The proposal was sponsored by the DIGISTAR 
division of Evans and the  International AVS Center in cooperation with 
Advanced Visual Systems Inc.,  CONVEX Computing Corporation, 
Digital Equipment Corporation, Hewlett- Packard Company, IBM, SUN 
Microsystems and Wavetracer Inc.  In addition  there are numerous 
groups around the world that are filling the role as affiliates  and will 
participate in part of this collaboration.  Affiliates include Xerox 
 Corporation, Bussan Advanced Systems, North Carolina 
Supercomputing Center,  SET Technology, Waterloo Maple 
Software,and others who are still being  processed.

We have a 20 foot dome projecting visualizations from the DIGISTAR 
onto an  overhead hemisphere.  This is similar to what you may have seen 
in a  planetarium, but instead of analog it is digital.  This demonstrates 
the emerging  large scale presentation technologies that will be essential 
in dealing with the  large quantities of data that are currently being 
created.  It will demonstrate high  spatial fidelity and participatory 
involvment.  We will have approximately ten  AVS Consortium 
workstations around the perimeter demonstrating real world  applications 
using these workstations with AVS and demonstrating how scientists  are 
beginning to solve real world problems with visualization environments 
in a  distributed, heterogeneous and collaborative method.  We will be 
demonstrating  the DTM protocol (developed at NCSA) as an AVS 
module for collaborative  working among different scientists working on 
the same data set from remote  sites and other interesting demonstrations 
which are currently being designed.   Entire focus is on real science being 
done today.

We are bringing together about one and one half million dollars in 
equipment,  space, connections and expertise to allow us to begin to show 
the world how  scientists can begin to work together in truly collaborative 
way with todays  technology.  Stop by and say hello!
 
VOLUNTEERS NEEDED!

Many of you have volunteered to assist the IAC where needed once we 
were  through the initial start up phase.  We would like to solicit 
volunteers to help with  next years AVSU93 Conference.  In particular, we 
need individuals to chair  several lecture tracks and coordinate speakers, 
etc.  We need individuals to  prepare and coordinate panel discussions.  
We also need people to work with the  AVS Consortium to assist and 
advise them on several Workshop tracks.  We  would also like a 
volunteer from the west coast to work with us to begin  preparations for 
AVS U94 and a volunteer from Europe to work with us preparing  for 
AVS U95.
 
WAIS and AVS 
Steve Thorpe, International AVS Center

The International AVS Center now has over 250 modules available on 
our 
anonymous ftp site for you to make use of.  These can be obtained via 
 anonymous ftp to avs.ncsc.org.  Please see the file AVS_README at 
that  address for more information on the ftp site and the International 
AVS Center.  With so many modules available, it can be difficult to find 
the modules you need  to solve your particular problem.  To help you 
wade through our ftp site, there is  a Wide Area Information Server 
running.  WAIS allows you to ask an English  language query of the 
server, and a ranked list of relevent documents is returned.   You can then 
retrieve the documents that seem appropriate.

There are two WAIS indexes, or databases, that are available for your 
use.  One  is an index of all of the .txt files that go along with the modules 
at the ftp site, and  other text files at the IAC.  The second index has just 
been created - it is an  archive of all of the postings to comp.graphics.avs 
starting with May 1992  postings.

To get started with WAIS, please read the ftp site's file 
WHAT_IS_WAIS, and  check out the WAIS client module on the ftp site 
called awais.  This is an AVS  module that will allow you to peruse 
through a wide variety of WAIS sources on  the Internet, including the 
International AVS Center's.

For example, I might be interested in JPEG files, so I might ask the server 
the  question: "Can I read or write JPEG files using AVS?"  A typical 
response from a  WAIS client that you could type your question into, 
would be as shown below.  I  could then select any of these documents 
for viewing or downloading from  within AVS.

AWAIS		Search Results	Items: 8
  #	Score	Source	Title	 Lines
001:	 [1000] (  AVS_TXT_FILES	 AVS_README	 589
002:	 [ 844] (  AVS_TXT_FILES)	AVS_CATALOG	2008
003:	 [ 603] (  AVS_TXT_FILES)	write_jpeg	459
004:	 [ 592] (  AVS_TXT_FILES)	read_jpeg	 456
005:	 [ 413] (  AVS_TXT_FILES)	WHAT_IS_AVS	290
006:	 [ 380] (  AVS_TXT_FILES)	FAQ	 274
007:	 [ 184] (  AVS_TXT_FILES)	read_HDF_SDS	198
008:	 [ 184] (  AVS_TXT_FILES)	read_abekas_ 	116
 
AVS '92 - A Review

The first International AVS Users Group Conference was held February 
11-13,  1992.  The  conference was hosted by the International AVS 
Center at the North  Carolina Supercomputing Center in Research 
Triangle Park, North Carolina.  In  cooperation with Advanced Visual 
Systems Inc, CONVEX Computer  Corporation, Digital Equipment 
Corporation, Hewlett-Packard Company, IBM,  SUN Microsystems, and 
Wavetracer Incorporated.  There is some comnfusion as  to what the AVS 
Consortium means.  The above companies represent the group  of AVS 
Vendors that are funding the International AVS Center and promoting 
 the development of scientific visualization using AVS.  There are many 
 additional platforms that AVS is ported to and information on those 
companies is  available through Advanced Visual Systems Inc.  Only 
Consortium members are  represented in any International AVS Center 
activities since it is their money,  equipment and moral support that 
directly sponsors this center for AVS users.  Originally, we had 
anticipated about 50 participants at the conference.  This was  not from 
lack of interest, but rather from lack of time.  We started putting pen to 
 paper in October and by the time we got the advance registration forms 
back  from the printers and out in the mail it was mid-December.  With 
only 6 to 8  weeks to respond and in the middle of the holidays, 50 
seemed like the most we  would be able to reach.  Unsure of what the 
first audience would be, we opted for  a 50/50 approach for both new and 
advanced users and also a 50/50 approach for  academia versus 
Industry/laboratory.  Surprise!  Registration quickly grew to 80,  100, 125 
and we had to make alternate arrangements for locations of our lectures 
 and add additional computers to the tutorials and workshops rather 
quickly.   Including attendees, speakers and vendors, we passed out 240 
registration packets  on the first day and another 20 or so on day two and 
three.  We turned away a  little over a hundred the week prior to the 
conference. The only notice that was  sent included my personal email 
file, some advance registration forms to the  vendors which went out late, 
and word of mouth.  We were quite stunned as well  as pleased at the 
response in such a short time period.

The idea of having a 50/50 (Intro/Adv) set of lectures, tutorials, etc was 
off base.   While everyone seemed to enjoy themselves and come away 
with lots of new  friends and ideas, almost everyone wanted more 
advanced and more technical  goodies the next time.  We are already 
working on plans for next year and we  will have many different 
discipline specific tracks and more depth.  Everyone  wanted more hands-
on tutorials and workshops next year.  We are also working  on that idea.  
The next issue of AVS Network News will explain some of our  plans for 
next years conference.  We would appreciate your opinions.  At first we 
 were a little surprised that we only had 10% from acedemia.  We think 
the reason  that we only had about 10% from academia was due to our 
mailing list.  Our  contacts are mostly from companies and laboratories, 
etc.  We will make sure to  get it out to the university community more 
thoroughly next time.

We set up about 16 ad hoc user groups around the world.  This is being 
 coordinated currently by Stephen Franklin.  We want to have many 
Special  Interest Groups and there were many volunteers to help.  We 
were both pleased  and impressed by the way the attendees volunteered to 
help not only with user  groups, but with next year's conference, special 
interest groups, advice and  consultation and so forth.  We really felt that 
it was a "users" conference and we  tried very hard to keep it that way.  
The artile titled "AVS User Groups" will  explain how to join, how to set 
up your own, how to coordinate these groups with  the international user 
group, how to get on special interest group mailing list,  how to volunteer 
to help and so forth.  There were about 15 people from Europe  and 
Japan.  The countries represented were France, Germany, Austria, 
 Switzerland, Finland, Denmark, UK, Spain, Taiwan and Japan.

All of us were very pleased and excited with the level of interaction 
between all  of the attendees.  There were no wall flowers, everywhere 
one looked there were  groups meeting, talking, excited about finding 
new friends and collaborators.  A  major effort was made to keep the 
vendor focus out of the conference.  They  were there and willing to 
answer questions, show their products and advise, but  had nothing to do 
with organizing any portion of the conference.  There were  only a couple 
of times things slipped by us, but you canUt win them all.  We are 
 currently putting together a packet to send to the attendees. It will 
include an  updated attendee list, user group information, order forms for 
videos of the  lecture series, several questionaires on what users would 
like to see the center  provide or provide better, areas of interest, projects 
users would be interested in  collaborating on with other users, and many 
many more topics.  If you would like  to be added to this list, send your 
address to me via email at avs@ncsc.org or to  the International AVS 
Center, 3021 Cornwallis Road, RTP, NC 27709.  Numerous people 
volunteered to donate modules to the center and we want to  encourage 
others to do the same.  We started a tape exchange program whereby if 
 one does not have net access or for reasons of security or other 
difficulties we can  rotate a tape of the ftp site every 4 to 6 weeks.  We 
send the modules we have and  the individuals on the other end send 
anything they are able to collect back (if  any).  If you need the same 
service send a note to the address listed above.
 
Obtaining Modules

Modules may be obtained by two basic methods.  The first is the standard 
ftp  protocol.  When you ftp to avs.ncsc.org, a menu will come up that 
will guide you  in using the ftp site and point you to the AVS_README 
and the  AVS_LICENSE files.  The AVS license agreement must 
accompany all modules  obtained and is self-explanatory.  The 
AVS_README file provides considerable  information on the site and 
how to obtain and submit modules.  There is a new  AVS_CATALOG 
file that is updated daily and printable and there is also a  PostScript 
version of this catalog.

When you login to the AVS directory at avs.ncsc.org, you will see 
subdirectories  called DATA, FILTERS, MAPPERS, RENDERERS, 
MISC, and  SAMPLE_DATA and SUBMIT.  Some modules have 
multiple purposes and will  be placed in the most appropriate directory.  
SAMPLE_DATA will be for data  that is donated but has no associated 
modules.  When you cd to the subdirectory,  you will see many 
makefiles, such as make.convex or make.dec -- one for each  port of the 
module and its associated files.  This will include source code, help  files, 
README files, scripts, sample networks, etc. 

The second method for obtaining modules is through standard email.  
When you  send an email message to avsemail@ncsc.org, you receive an 
automated listing  of all available modules along with a request form and 
copy of the AVS Catalog  (updated daily).  When you return the request 
form to avsorder@ncsc.org, you  receive the modules and associated files 
(subject to size considerations) through  normal email channels.  Full 
information on this procedure is sent with the initial  automated mail 
response.

While this ftp site presently is not too difficult to peruse, it quickly will 
entail a  large maze of directories.  With the large number of anticipated 
modules this will  make it difficult to traverse through all of the 
directories.  Therefore, we have  provided a X interfaces and a command 
line program using WAIS protocol  (client).  There is a 
WHAT_IS_WAIS file you can download and read for more  detailed 
information.  This is also available as an AVS module called awais.  This 
 is a hypertext search-and-query program that enables you to type a 
sentence in  standard English language (e.g., <Show me all the filters that 
are related to  molecular modeling.>) and receive a listing of everything 
relating to that  particular request.  You then can read the man pages or 
look at the source code  and decide what you want.  You will be able to 
click on a window and have the  modules and their associated files or any 
subset ftpUd to you automatically (not  currently available, expect by end 
of summer).   You also will be able to use the  WAIS interfaces for 
exploring information from AVS newsgroups and other  AVS related 
topics.  

If you do not have network capability, you may request a tape via U.S. 
mail.   Send a tape and a $5 postage-and-handling fee along with your 
request.  You  should state the vendor type, machine type, and operating 
system.  We then will  send you all available files in those categories, 
such as DEC, DEC5000, and  OS4.0.  If you do not provide a tape with 
your order, you must include tape cost.   Tapes will not be available from 
the Center until its porting facility is completed  and tape needs and 
module-to-tape downloading time have not been determined.   As 
additional order information becomes available, it will be posted to the 
AVS  newsgroup, included in AVS Network News, and made available 
through your  AVS vendor.  Special requests for tapes of modules can be 
made to  avs@ncsc.org and will be handled on an individual basis for 
now.  An automated  procedure to be completed by Summer 1992, will 
accelerate this process.
 
TRADEMARKS IN THIS ISSUE

AVS is a trademark of Advanced Visual Systems Inc.
CONVEX is a registered trademark of CONVEX Computer Corporation
DEC is a trademark of Digital Equipment Corporation
IBM is a registered trademark of International Business Machines 
Corporation
Stardent is a trademark of Advanced Visual Systems Inc.
SUN is a registered trademark of SUN Microsystems Inc.
UNIX is a registered trademark of UNIX System Laboratories Inc.
X-Window System is a trademark of the Massachusetts Institute of 
Technology
 
International AVS Center Module Highlights
Steve Thorpe, International AVS Center
 Abstract

This article highlights several useful modules freely available to the AVS 
user  community from the International AVS CenterUs module repository.  
It also  reviews the procedure for obtaining or submitting AVS modules. 

Introduction
 
The modules fast_animate, color_legend, and contour are briefly 
described and  demonstrated.  For further information on obtaining these 
and other modules  please see the section , "Using the module 
repository".  

Animating a sequence of geometries

Keith Refson, of Oxford University has written a module called 
fast_animate.   This coroutine module reads a sequence of  geometries 
into memory, then fires  these objects to its output port in rapid 
succession.  Since the geometries are stored in memory, the speed of the 
animation is significantly improved as compared to reading each file just 
before firing that geometry. Given sufficient  memory, the animation rate 
will remain the same regardless of the number of  geometries. 

A user with a sequence of geometry files to animate within AVS would 
typically  follow the file naming convention of "rootN.geom" where 
"root" would be some  base name for that sequence,  "N" an  integer 
representing the frame number for  that particular geometry, and ".geom" 
the default suffix for these geometry files.  A mechanism for other 
naming conventions is provided via printf format  characters such as %d, 
%o, and %x.  Supplying these within a name to  fast_animateUs file 
browser will enable the  module to handle more arbitrary file  names. 
 
Incorporating fast_animate into an AVS network is quite trivial (see 
figure 1).   Simply connect its output port to the geometry viewer and you 
have a complete  network.  Entering the min and max frame numbers for 
the appropriate  parameters, selecting one of the files in the sequence with 
the file  browser, then  clicking on the "go" widget will cause the entire 
sequence to be read into  memory.  At this point, clicking on "go" will 
toggle the cycling of the  animation.   The "min" and "max" parameters 
can be used to select a  subset of the sequence  for viewing; the "step" 
and "back" buttons allow the user to single step through  the sequence.  
This module can be found on the International AVS CenterUs ftp  site in 
the directory "DATA/fast_animate".

Generating a color legend

Wes Bethel of the Lawrence Berkeley Laboratory has provided the AVS 
user  community with a useful module called color_legend. This mapper 
module  accepts a colormap as input, and generates a legend suitable for 
rendering with  the geometry viewer.  The entire range of colors in the 
colormap is shown as a  smoothly shaded color bar, which can be labeled 
and oriented using  color_legendUs widgets.     From color_legendUs 
control panel, the user can choose whether to include a 1  pixel thick 
border around the bar, adjust this borderUs gray scale, and choose the 
 number, size, font, gray scale and precision of the labels.  The user can 
choose a  vertical or horizontal orientation for the color bar, reverse the 
order of the colors,  and toggle whether boundary lines are shown on the 
color bar at the location for a  particular label.

The example network shown (see figure 2) creates a visualization of the 
sample  AVS dataset called hydrogen.dat, which depicts the probability  
of an electron  being found around the nucleus of a hydrogen atom.  
Other modules used in the  network include arbitrary slicer and volume 
bounds.  This module can be can be  found in the directory 
"MAPPERS/color_legend".  Creating contour lines in a 2d scalar field

The filter module contour was supplied to the International AVS CenterUs 
ftp  repository by the former Stardent Computer Inc.  It can be used to 
create contour  lines on a black background within a  "field 2D  scalar 
byte" extracted from  image data.  The user is supplied with two dial 
parameters.  With the "threshold"  dial, the level of the contour lines 
being created is set.  With the "new" parameter,  the color index used for 
the contour lines  can be selected.  

The algorithm in contour is straightforward.  For each pixel in the new 
image,  the corresponding pixel in the original image and the 3 pixels 
above and to the  right are examined.  If among these 4 original pixels, 
there is at least one pixel  with a value above the threshold, and at lease 
one with a value less than or equal  to the threshold, then the new pixel 
becomes part of a contour line.  Otherwise,  the new pixel is set to black.  
This module can be can be found in the directory  "FILTERS/contour".

Using the module repository

To obtain detailed information about the International AVS Center (IAC), 
send  any email message to avsemail@ncsc.org.  You will automatically 
receive two  replies:  the latest copies of AVS_README and 
AVS_CATALOG.   AVS_README discusses what the IAC is all about, 
and AVS_CATALOG  summarizes the currently available modules.  
There are three methods for  obtaining modules discussed in detail in 
AVS_README:  

1)	standard ftp protocol using anonymous ftp to avs.ncsc.org
2)	automated email module retrieval for users without the ftp 
protocol, via an 
	"order" message sent to avsorder@ncsc.org
3)	batch tape requests mailed to the International AVS center

The IAC has recently implemented the Automated Porting Tool (APT).  
This  enables "push button" porting of submitted modules across the 
hardware  platforms at the IAC.  Now that this infrastructure is in place, 
you are strongly  encouraged to submit your AVS modules to the IAC.  
Donating a module to the  IAC benefits  the entire AVS user community 
by facilitating further use of AVS  to  visualize complex scientific 
phenomena.  Any module that is not  donated  may be rewritten 
elsewhere, wasting valuable time and hindering further  development of 
other module capabilities for everyoneUs benefit.    There are three 
methods to submit modules.  Each of these is discussed in detail  in the 
file AVS_README:

1)	Standard ftp protocol
2)	email (no binaries)
3)	Sending tapes to:	

		The International AVS Center
		P.O. Box 12889              
		3021 Cornwallis Road
		Research Triangle Park, NC 27709
		USA


If you are having any problems making use of the module repository after 
 reading the file AVS_README, please send email to avs@ncsc.org, 
and your  questions will be promptly answered by one of the IAC staff.
 
What's New?

There is now an archive of all traffic on comp.graphics.avs at the 
International  AVS Center ftp site avs.ncsc.org ( 128.109.178.23 ).  Thus 
if you know of  anyone, whom does not have news access, they can 
download the files in the  COMP.GRAPHICS.AVS directory.  These 
files are in the standard mailbox  format so that anybody can peruse these 
files using any mail utility with the -f  command.

For example:  Mail -f May_92.  If a "message" in this mailbox is replied 
to, then  a message is sent back to the poster of the article - but it is not 
replied to the  newsgroup.  The files will be stored in a separate mailbox 
for each month:  May_92 Jun_92.

Also, if you know of someone who does not have ftp access, then there is 
a sister  mailing list to the newsgroup established now as well.  This 
mailing list is being  maintained by the listserv utility. Users can add and 
delete themselves from the  mailing list at will through this utility.  If a 
user wishes to be added to this  mailing list, they should send email to 
listserv@avsusers.ncsc.org with a body of  one line: HELP.  This will 
return email on a large number of AVS mailing lists,  including the 
avs_newsg mailing list.  All postings to the newsgroup will be  forwarded 
to this list; however, separate postings to this mailing list are not 
 currently being posted to news.  If anyone has any suggestions on 
improving  these utilities or any other IAC facility, please let us know.

There is now a shadow ftp site in the United Kingdom.  This is being 
maintained  courtesy of Steve Larkin from the United Kingdom.  You can 
access this site by  ftp at hpb.mcc.ac.uk (130.88.200.7).

It is no longer necessary to send a Submission Release form when 
donating  modules.  Wording in the headers and licensing of the site has 
changed to take  care of this issue.

The Automated Porting Tool is up and running in beta mode.  It currently 
has an  80% sucess rate for the platforms ported. 

 Development of a VHF/UHF Broadcasting Planning and 
Visualization System  on the basis of AVS

Walter Schmeing, VISTEC Software GmbH and Franz Rothe, DBP-
TELEKOM 
FTZ

Summary

Deutsche Bundespost TELEKOM (Technical Engineering Centre in 
Darmstadt)  has developed a broadcasting and visualization system to 
simplify and accelerate  the planning of broadcasting transmitters.  The 
coverage situation of broadcasting  transmitters is visualized by this 
application program in connection with other  data, such as maps or 
geographical information.  For the optimization of the  coverage 
situation, various technical parameters of the transmitter site are used.  
 The changed situation of coverage, resulting from this, is immediately 
visualized.   This interactive planning system is based on AVS.

Introduction

Basic Problems with Broadcast Planning

Before a transmitter station can be put into operation, the following 
technical  problems have to be solved, during the planning stage of 
broadcasting  transmitters and transmitter networks: 
	selection of location
	frequency ascertainment
	assessment of the coverage situation to be expected
 When searching for the most favorable location for the transmitter 
station, a  detailed knowledge of the surrounding terrain in the future area 
of coverage is  required.  This can be achieved either by site inspections 
or by inexpensive  computer simulations on the basis of a digital terrain 
model.  In the case of simulation, the planning engineers can use their 
computer to  perform all necessary investigations, e.g. variations of the 
transmitter site or  antenna height.  Moreover, they are able to find out 
whether there are any  geographical impediments which can obstruct the 
view of the selected area of  coverage.  They can take advantage of 
mountains surrounding the area of  coverage by using them as a 
protection against interfering influences.  An  efficient simulation close to 
reality is, however, dependent on the quality of the  basic data applied.   
Altimetric and land usage data, scanned map material, and political and 
 economic data form the basis for the definition of a planning project by 
means of  the system described.  After a suitable location has been found 
and other  technical parameters of the transmitter station (transmitting 
power, operating  frequency, antenna characteristics) have been specified, 
the theoretical coverage  is ascertained with the aid of a wave propagation 
model.  Field strength and  coverage data are calculated for each segment 
of the area under consideration.   They are then superimposed on other 
available information and then visualized.   The representation should be 
in such a manner, that it is easy to modify and  understandable to non-
professional viewers.

Description of the Application

The graphically supported planning system comprises the following 
stages,  which can be performed with the help of the AVS application: 
	definition of the planning project
	simulation of the site inspection on the basis of the digital terrain 
 model
	visualization and optimization of the coverage situation
	explicative display
 The intuitive structure of the implemented AVS menu is intended to 
support the  planning engineer in his/her work.  They activate the 
necessary stages for the  planning of broadcasting transmitters by 
selecting the appropriate sub-menu  (Figure 1).  The various planning 
stages are performed as described in the  following:

Definition of the planning project - The planning project is defined by the 
 coordinate frame of the area of coverage under consideration.  
Supplementary  data or coverage is loaded into this frame, if required.  
After definition of these  project parameters  (Projekt Parameter module) 
by the planning engineer they  are stored in a file and are available for 
further use (Figure 2).

Simulation of the site inspection on the basis of the digital terrain model - 
To  become acquainted with the surrounding terrain and its influence on 
the wave  propagation, the planning engineer can cut out terrain profiles 
(Gelandeschnitt  module).  With the help of the mouse, they define a line 
within the project area.   The altimetric profile along this line is then 
displayed in an additional window  (Figure 3).  In another window, a 3D 
projection of the digital terrain, including  map and coverage information, 
is displayed.  This 3D representation can be  optionally rotated with 
standard AVS tools and demonstrates planning problems  (Figure 4).  The 
visibility concept (Einsehbarkeit module) allows a first  approximation at 
the coverage by the transmitter site.  After having selected one  potential 
transmitter and the relevant geographical conditions, those areas being  in 
sight of the transmitter are marked by means of TELEKOMUs altimetric 
 database.  Now the planning engineer is able to make a first useful 
selection of  the transmitter site, since it is highly probable that visible 
areas are also covered  areas (Figure 5).
 Visualization and optimization of broadcasting coverage - For 
visualization  of the coverage situation of the project area, the predictive 
data of the required  transmitters calculated by means of the wave 
propagation model, are loaded into  the application using the load 
transmitter module and are superimposed on the  other data selected, such 
as maps.  They are displayed in a 2D window, the  contents of which is 
then additionally mapped as a texture onto the terrain model  in the 3D 
representation (Figure 6).  By the selection of various transmitters or 
 planning variants, it is possible to show their influence on the coverage 
of the  project area (Figure 7).  With the appropriate dial made available 
by AVS, the  power of the transmitter under consideration can be 
modified with its predictive  data being adjusted accordingly and 
visualized at once.  Furthermore, it is  possible to modify the pattern of 
the transmitter under consideration with the  antenna characteristics, the 
field strength values of the field strength prognosis  being updated in the 
relevant angular ranges (Figure 8).  The representation can  be influenced 
by a wide variety of control parameters.  Changes of the planning 
 situation are immediately obvious.  In addition, the user can see 
segments of the  area of coverage by mouse control (zooming) or can 
display or suppress  additional information.

Explicative display - The color pattern of the representation is determined 
by the  color definition making it possible for the user to optionally select 
legend and  colors (Figure 9).  In order to get a hard copy of the results of 
visualization, a  high-quality printer is connected to the system, printing 
out the images selected  by the user in "photo" quality.  Furthermore, the 
system produces a text file,  containing information on the project and the 
transmitters selected.

Use of AVS

One of the main purposes of this application is to provide the user with a 
clearly  arranged interface which is also easy to handle.  An AVS module 
was developed,  transmitting commands (CLI commands) to the AVS-
kernel to control the  display and suppression of the requested menu and 
to create or delete any  required display windows.  This module has a 
permanently displayed information  window, continuously providing the 
necessary information to the user.  All AVS  modules were programmed 
in such a way that their information  texts will also be  transmitted to this 
information window (by sending appropriate CLI commands).

To grant the required interactivity in the application, an X11-based 
picking  module was programmed.  This AVS module shows an 
incoming image in an  X11 window and registers any mouse events in 
this window.  It is possible, for  example, to draw a line or a box (rubber 
band), the end points of which are then  available at the output port where 
they can be picked up by other modules as XY  pixel coordinates.  
Zooming into the project area shall serve as an example for  that.  After 
having selected the zoom area by drawing a rubber band in the 2D 
 display window, its corner coordinates are sent to the upstream module 
 generating the 2D image.  It converts pixel coordinates to user 
coordinates (in  this case geographical longitude and latitude) to generate 
the image for the  zoomed area.  These coordinates are required, e.g. for 
re-loading the map at its  maximum resolution when zooming the 
requested section.  The visualization in this application is mainly 
concerned with mixing the various  layers of data to be displayed.  This is 
done by a module especially programmed  for this purpose.  Any color 
images (five in this case) generated by various data  are converted into an 
image using the alpha value of the individual pixels being  used as a 
degree of transparency.  This "alpha value" can be defined separately  for 
each color class.  An AVS color module assumes this task, allowing an 
 interactive definition of the color values (alpha, red, green, blue) of the 
individual  color classes.  The color classes are defined in a legend 
containing for each  requested color number, a name and threshold value 
which are the link to the  coverage information.  After having read such a 
file, a legend is set up on the  basis of the names and the associated colors 
to indicate color classes and values  to the user.  The threshold value is 
used by other AVS modules, also reading this  file to give the required 
color to the data.  Thus, a user-friendly, interactive, and  flexible 
application could be developed on the basis of AVS.  Thanks to the use 
 of AVS, the development effort for this application could be restricted to 
5 man- months, which is only a small percentage compared to the 
traditional  programming effort.

Outlook

At present, two implementations of the AVS application are used by 
TELEKOM.   The application is of help in planning the broadcasting 
coverage for East  Germany.  The first version of the application was 
presented to experts on the  occasion of the Radio and Television Show 
(Funkausstellung) held in Berlin in  1991.  Currently, details of the 
system are modified and interconnected with  another database 
containing the numbers of inhabitants of states, districts,  communities, 
etc.  After having integrated these data into the system, it shall be  able to 
evaluate and display the supply of a certain area with reference to 
 population density.  Due to its flexibility and the standardized data 
interfaces, the  use of the application for any future radio planning 
procedures (DAB, HDTV) is  ensured.  The system can be extended by 
using other local graphic computers, so  that planning activities will no 
longer be a central task.  

Animating Time Dependent 3D Data Using 
AVS

Upul R. Obeysekare
Scientific Visualization Laboratory, Navel Research Laboratory, 
Washington, D. 
C.

In the process of conducting day-to-day research, scientists frequently 
need to  visualize events that unfold over time.  Animation is a powerful 
tool that helps  scientists to visualize these dynamical processes.  
Instantaneous visualization  provides information about a particular time 
step in the simulation, while  animation of these events can supply 
valuable information about the dynamics of  the process.

Typically, a scientist runs a long simulation on a supercomputer to 
accumulate a  large database of time-indexed results.  The data is then 
transferred to a  visualization platform for animation.  Major difficulties 
in executing these tasks  are portability of the data to different computer 
architectures and complexity of  creating the animation.  Developing 
tools and methods that perform these steps  conveniently and efficiently 
can result in the savings of valuable research time.

The Scientific Visualization Laboratory at the Naval Research Laboratory 
is  addressing these issues by developing a variety of tools for creating 
animations.   In the previous issue of AVS Network News (Winter 1992) 
we announced an  AVS module that animates data from Molecular 
Dynamics simulations.  Below  we describe an AVS module for 
animating 3D time dependant data. 

We have developed an AVS module, animate hdf volumes, that uses an 
HDF  (Hierarchial Data Format developed at NCSA) file with multiple 
frames.  In  practice a scientist runs the simulation on a supercomputer 
and saves frames at a  desired frequency to an HDF file.  The AVS 
animate hdf volumes module can  then read the file and output single 
frames to be used by other modules such as  isosurface or orthogonal 
slice.  The toggle button, "run", in the module, can be  used for 
continuous output while the "step" button can allow one to step frame by 
 frame.  The current coroutine supports only uniformly gridded data.  
NCSAUs  HDF turns out to be the best possible choice for data format 
since it is portable  and available on both supercomputers and a variety of 
workstations.  You can  contact NCSA directly or login to their 
anonymous ftp site at ftp.ncsa.uiuc.edu to  download HDF and the 
appropriate documentation.

One major difficulty encountered in creating animations is the relatively 
large  amount of data which needs to be handled.  Frequently scientists 
cannot save  every time step in the file.  As an alternative we added the 
capability of  performing interpolation.  Although this method may 
generate excessively  diffused intermediate data, one can use it as a 
compromise solution when disk  space is limited.  Interpolation can result 
in an unphysical pulsating effect in the  animation, which is reduced if the 
two datasets used for the interpolation are  chosen to be more closely 
spaced in time.
 Figure 1 - 4
Shown here are four frames at different time steps from a computer 
simulation of  an underwater explosion bubble broaching the free surface.  
The darker  isosurfaces on top are the air water interface as seen through 
air, while the lighter  isosurfaces on the bottom are the same interfaces 
seen from the water side.  This  data was generously supplied by Dr. Jay 
Boris from the Laboratory of  Computational Physics and Fluid 
Dynamics at NRL.  

Module Submission Criteria
 We encourage modules of all types.  We are not looking for perfect  
code, but  rather code that is used everyday and would be useful to users.  
Several users  have  said they did not think their code was good enough 
or would be useful to  the AVS user community.  This is not true.  We 
have many different levels of  users - from the total novice to the 
experienced professional - and code is needed  for all levels.  All we 
require is source code, a makefile and either a readme or  man page.  
Data, networks, etc are strictly optional.

Source file and Makefile - Source code and Makefile must accompany all 
 modules submitted.  We encourage extensive commenting and ask that 
port- specific lines be so commented.  

Module description - A detailed description of the module must be 
included  with its submission.  This may be in the form of a man page or 
ASCII text format  (as in a README file).  Module description is one of 
the most important criteria  for submission.  Please note if multiple 
modules are in one source code file.  The  International AVS Center staff 
will rewrite the documentation as necessary.  

Data - If your module uses a nonstandard data format, you must include 
an  example (not necessarily real) of that data.  Explanations of how to 
read the data  should be placed in the required manual or README file.

Miscellaneous - You are requested to provide sample networks and 
scripts when  appropriate.

To submit modules, ftp to avs.ncsc.org and cd to the SUBMIT directory.  
You  will be prompted in how to create a directory.  The directory itself 
will be  invisible so that others may not inadvertently copy over your 
files.  When you are  in your directory, use standard ftp protocol to 
submit your modules and  associated files.  Information on using ftp for 
basic submission and retrieval can  be obtained by sending a request to 
avs@ncsc.org.

You also can submit modules and associated files by email to 
avs@ncsc.org and  by tape (tape will be returned if requested) to the 
International AVS Center,  3021 Cornwallis Road, RTP, NC 27709.
 
The AVS to Video Connection
Terry Myerson, International AVS Center
 
With millions of video tape recorderUs installed in the United States 
alone, video  is proving to be the most portable presentation medium for 
computer graphics,  and more specifically scientific visualizations.  The 
process of recording  computer graphics to video is a complicated one, 
that requires both hardware and  software support.  On the hardware side, 
sequences of digital frames need to be  translated into interlaced analog 
signals for recording - but this is an issue for  another article - another 
day.  This article is intended to address the current  module support for 
recording AVS visualizations to video tape.

There are currently 4 modules, with source code, available to the AVS 
user to  assist in the video creation process.  Brian Kaplan of the 
University of Indiana  has submitted a module to the International AVS 
Center module repository called  Record which supports recording with a 
Lyon Lamb Mini-Vas, or separately to a  Sony Videodisc Recorder.  The 
Lyon Lamb module support was originally  developed at Stardent, but 
has been greatly enhanced in the Record module.  The  Lyon Lamb 
device is an animation controller that allows frame accurate  recording to 
a large number of video tape recorders.  This device requires an  encoder 
and sync generator to complete the hardware requirements for recording.  
 The Sony Videodisc Recorder is an analog frame storage device which 
accepts  Red-Green-Blue analog input similar to a workstation monitor - 
but at NTSC  scan rates.  The Sony device would need a sync generator 
and scan converter to  complete the hardware requirements for recording.  
The Lyon Lamb setup would  cost approximately $5,000, while the 
Videodisc setup would cost approximately  $12,000.

Wade Smith of Convex has submitted a module named output A60 that 
writes  images directly to an Abekas A60 digital disk recorder.  This 
module is the  successor to Ian CurringtonUs write abekas, and Terry 
MyersonUs write A60 yuv  module - both of which also support the 
Abekas A60 device.  The A60 accepts  frame files over a TCP/IP 
network, does not require external sync, and can  playback to any 
commercial or industrial grade video tape recorder with no  degradation 
of image quality.  The hardware setup which this module supports is 
 approximately $65,000. 

Included with the AVS 4 Animation Application, there are two modules 
which  support the video creation process : output VideoCreator, and 
output  ImageNode.  These modules are both distributed with source 
code, and thus do  not require the separate licensing of the Animation 
Application.  The output  VideoCreator module supports the Silicon 
Graphics VideoCreator product  which includes several components in 
one product : frame buffer, scan converter,  encoder, sync generator, and 
animation controller. The output ImageNode  module supports the 
Diaquest ImageNode product, which just like the  VideoCreator includes 
several components in once product: encoder, sync  generator, and 
animation controller   Neither of these products require any  external 
hardware support for video production.  Each of these systems would  run 
approximately $10,000.  

For the AVS user, each of these modules allows the visualizer to hook up 
a  module within an AVS network, and output a frame sequence directly 
to a video  tape ( Mini-Vas, Video Creator, or Image Node ) or output a 
frame sequence to a  frame storage device for later playback to video tape 
(Videodisc or A60 )  assuming you possess among the other hardware 
peripherals, a video tape  recorder!!

The modules listed above are all that are currently available at the 
International  AVS Center - the hardware they support is not specifically 
endorsed by the  center.  If there are AVS users out there, who have 
written modules to support  other video hardware, submitting them to the 
module repository would make the  video creation process simpler for 
everyone.


