 ______/\___________________________      __  ________________ ___  /\_______
 \____   \  ________ _   _ ______   \    /  \|  \  ________   |   \/  ______/
 /   |    \  _)   \   \_/   \   |    \  /    \   \  _)   \    |    \______  \
/    |     \       \   |     \  |     \/          \       \  /~\    \    /   \
\_____     /_______/___|     /________/\____\_____/_______/_________/________/
 ===\_____/============|____/========================================[+tZ^]==

                              DemoNews Issue #81
                     January 29, 1995 - February 4, 1995

                                 ------------

  DemoNews is a weekly publication for the demo scene. It is produced at the
   Internet FTP site  ftp.eng.ufl.edu (HORNET).  This newsletter focuses on
  many aspects of demos and demo making. Everyone is welcomed to contribute
                    articles, rumors, and advertisements.

    Information about HORNET and DemoNews can be found under /demos/README

Start.of.DemoNews.081,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.part.1.of.2

SIZE:  53,434  SUBSCRIBERS:   Last week: 1220   This week: 1241   Change: +21

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

             SECTIONS          ARTICLES
             ----------------  -----------------------------------
             General           HORNET has been busy!
             New Uploads       Files recieved at HORNET
             NAID              Survival Guide
             Editorial         General Protection Relationships
             Code              Ctrl-Alt-Delete, Now Its a Game!
                               Assembly Part 3 (It ain't no party)
                               BSP Trees
             Back Issues       How to Get 'em, Descriptions
             Closing Comments  Quote for the Week, etc.

.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,

 <<General>>

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

_____HORNET has been busy!

  Here are just a few things I would like to make the readers of DemoNews
  aware of:

  -ANSI:  The ANSI is back on HORNET!  After more flames than I could count
  (even with my socks off), I have decided to have an area on HORNET where
  the "packs" will be stored.  Syntax Error (organizer of iCE) is now
  HORNET's main coorespondent in this field, and he will be maintaining the
  files in this area.  However, there will not be an /incoming/ansi
  directory, only a /demos/ansi. Most of the previous problems stemmed from
  misuse of the /incoming/ansi directory.  Syntax Error will keep up to 10
  megs of the most current and wanted packs on HORNET.  He will be
  personally responsible for keeping this directory updated.  Also, any
  ANSI-related mail will be forwarded to him.  You can reach Syntax Error at
  syntax@io.com.

  -MC3PLAY:  MikMak, Rao, Stony, and Air Richter are currently working on a
  Music Contest ]I[ player.  This will be used by the judges and contestants
  alike for playing MC3 entries.  Remember, this contest will be officially 
  announced at NAID on April 15, 1995.

  -DNDP:  DemoNews Plus for DOS.  Ior, Psibelius, and Zoltar are currently
  working on a DOS-based version of DemoNews.  More than a plain vanilla-
  ascii reader, this is a full-fledged diskmag!  It will include graphics,
  music, additional articles from the DemoNews staff, and best of all, will
  be released on a MONTHLY basis.  Stay tuned for more details.

  -DN/HTML:  Jeff (White Noise) / HORNET deserves a lot of appreciation.
  In the past couple of weeks, he has made enormous strides in making the
  World Wide Web version of DemoNews come to life.  As the entire DemoWorld
  project becomes more concrete, you can expect quite a bit of coverage of
  it in DemoNews.

  -SLACKING:  I have been very slow in getting two interviews done.  The
  first is with Stone/Dust, and the second is with Gore/FC.  I finally got
  the questions out to Stone, but the Gore interview still has yet to take
  shape.  My apologies to these two individuals as well as the readers of
  DemoNews for the delay.

  -NEW FACES:  Two new individuals have joined the staff of HORNET as
  columnists.  They are Tom Verbeure and GraveDigger.  I met Tom through
  Jason Nunn (dee-cug, another DN columnist and friend).  Tom is an expert
  in the nuiances of hard core Assembler.  GraveDigger is another new
  addition.  Recently he did an incredible review of the Egg music for
  DemoNews, and this week he has done a "Survival Guide for NAID".  I am
  very pleased to have both of these gentlemen furthering the HORNET mission.

  -LISTSERVER:  There are two people not mentioned very often in this
  newsletter who do a lot of work for HORNET.  Pi is the TRUE listserver
  coordinator for HORNET.  Whenever the listserver crashes or goes buggy,
  Pi is the guy I count on to bring it back up.  In a slighly different area,
  Martin M. Pedersen does one of the janitorial jobs here at HORNET.  :)
  Each week when DemoNews goes out, I recieve lots of bounced mail
  notifications.  I forward all of these to Martin and he sends me a list
  of who I need to (un)subscribe or help out.  This is not a fun job and I
  really appreciate his help.

  -ASPHYXIA TRAINER:  Over the past several months, I have been working on
  converting Denthor's "VGA Demo Trainer Guide" source code from Pascal to
  C++.  In the background of the whole thing, FateGrinder and I shoot around
  ideas about how to optimize different assembler routines, etc.  If you
  look at my code hard enough, you're bound to find some of his influence in
  there.

  I know I'm forgetting something...  :)

.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,

 <<New Uploads>>

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
   NOTE: All locations start with /demos and then their respective sub-
         directory.  Please note however that the actual base directories
         (like /pub/msdos/demos) may differ from mirror to mirror.

Location          Filename.Ext  Size  Description
----------------  ------------  ----  ----------------------------------------

                                  /demos

/alpha/NEW        answer  .zip    40  Answer by Warlock of Amnesty
                  dfuse   .zip    10  Digital Fuse intro by Uncle Bob/Zion
                  einstein.zip     9  BBS Intro for Einstein BBS
                  friends .zip   875  Straight Line Connection for 3S Party 94
                  greetro .zip   199  Happy New Year by Sunrise
                  kiddo   .zip   132  A.P.E.X Presents an Intro called Kiddo
                  mciesc  .zip    14  BBStro for MCI Escapes by Subsystem
                  meet95  .arj   708  Something from Sti/Euphoria (GUS)
                  naidtro .zip   144  The NAID Party Intro (SB only)
                  southfix.zip    79  BBS Intro for South of Heaven by Omicron
                  tornado .zip    23  Shocker presents Tornado Intro (no mus)
                  xmas_dem.zip   658  Christmas Demo by The Paralytic Minds
/diskmags         bm9     .zip   580  Blackmail Issue #9 (stuff from TP94)
                  yahoo04 .zip   286  Yahoo #4, The Hangover Issue
/nets             dginfo18.zip    16  Demogroups Interchange InfoPacked v1.8
/news             nad_u01 .zip  1428  New Age Demo Database Upgrade: 1

                                    /code
/demosrc
                  fcsp2src.zip    31  FC's StarPort BBS ][ Source
                  incosrc .zip   241  Source to Inconexia demo by Iguana
                  isad2src.zip    20  ASM source for Immortal Syndicate BBS
                  kuk2src .lzh   159  Source for Pleasure Access BBS
                  sea_code.zip    33  ASM Source to Seasick / VLA
                  sqd1_src.zip    21  ASM Source to Squid1.com (BBS Intro)
/graph/lens       lenssrc .zip    40  BAS, ASM example of a Lens
/graph/pallette   fadecode.zip    30  C,ASM source for fades and pallette rot
                  palrot  .lzh     2  Pallette Rotate by Draeden / VLA
/graph/plasma     c_plasma.zip    55  C source code to color plasma
                  jclplasm.zip    88  ASM,C For NICE color Plasma
/graph/shadebob   jeffbobs.lzh    75  PAS source for Shade Bobs
/graph/tutor      tut9new .zip    43  Part 9 of Asphxia VGA demo tutor in C++
/pmode            dpmispec.arj    33  Protected Mode API For DOS Extended Apps
                  protect .lzh    15  ASM Protected Mode programming example
/sound            fmed101 .zip   147  OPL3 FM Sound Editor for Programmers
                  gp15-pas.zip    46  PAS source for GUS Modplayer
                  gusenv  .zip     1  ULTRASND environment checking in ASM
                  gusp15  .lzh    19  ASM source for GUS Modplayer
                  pps110  .lzh    84  Protracker Playing Source/Josh Jensen
/utils            basm10  .zip   297  Basic to ASM Language Translator
                  frmi!150.exe    38  Flat Real Mode Interface v1.5

                                   /music

/disks            f10_pck2.zip        Force Ten Pack #2
                  f10_pck3.zip        Force Ten Pack #3
                  f10_pck4.zip        Force Ten Pack #4
                  rot     .zip        Rotation by Neophyte mini musicdisk
                  traxx36 .zip        Latest Traxx album
/programs/frntend mplay12 .zip        Musicplay 12.0 frontend music program
/programs/misc    readcda .zip        Read digital data from CD using CDROM
/programs/players radv1_0a.zip        ADLIB tracker package (anyone use FM!?)
/songs/s3m        belly   .zip        Belly's Theme by Falcon (FM ADLIB)
                  cannabis.zip        Cannabis sativa by Transee
                  dnc2trnc.arj        Dance to the Trance by Hector
                  doom-hth.arj        Doom and Stuff by Hector
                  dreary  .arj        Dreary as all hell by Hector
                  epi-opus.zip        Opuscule by MusicMan/Epinicion
                  firesirn.arj        Firesiren by Hector
                  gonnadie.arj        We're All Gonna Die by Hector
                  k-udream.zip        Unfaithful Dream by Boomer the Bass Pig
                  messiah .zip        Messiah by Transee
                  mindrave.zip        Mind of a Raver by Avatar
                  mystwat2.zip        Myst Water by Hector/DMK
                  mystwatr.zip        Part 2 of the above
                  nois    .zip        Nois by Kevin, Fast drums & strange sou
                  pl_dt   .zip        Song by Plastique/Dep
                  pl_heart.zip        "
                  pl_know .zip        "
                  pl_move .zip        "
                  pl_rave .zip        "
                  pl_thund.zip        "
                  pl_uknow.zip        "
                  pl_who  .zip        "
                  pl_zany .zip        "
                  renais  .zip        Renaissance by Null
                  rh_cyu  .zip        Song by Red Horizon/Dep
                  rh_insom.zip        "
                  rh_nw   .zip        "
                  rh_ready.zip        "
                  rh_real .zip        "
                  rh_samur.zip        "
                  rh_sea  .zip        "
                  rh_tod  .zip        "
                  rh_vp2  .zip        "
                  sky_jung.zip        Jungle Baby Love by D.J. Skyjump
                  trn-imh .zip        In my Hough by Transee
                  trn-medi.zip        Mental Diary by Transee
                  wait4u  .zip        Waiting for You by Falcoln (Adlib)
/songs/xm         mftp    .arj        Music for the People by (see below)
                  moby-go .arj        Moby-Go by Pieter Van Den Veen
/text             life    .zip        Some text about a new group

.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,

 <<NAID>>

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

_____Survival Guide by GraveDigger

    +         .         /\
  .        + .      .  /  \    .    +
   _____ 3\ __3____    \__/_______             Official Survival Guide
   \__  \3 \  3\   \ +  __ \      \                    for the
  .  /   \  \  / _  \  /  \ \____  \  .   North American International Demo
    /  _     \/ /_   \/    \/    3  \                Competition
 . /    \____/    \__/   __/__       \           April 15 - 16, 1995
   \    /  . \____/  \__/  +  \______/ww
 :::\__/::::::::::::::::::::::::::::::::
 
 Here is a practical(?!) guide to surviving NAID, the upcoming North American 
 International Demoparty, which is to be held in Quebec on April 15th and 
 16th. There's still a few months left to prepare yourself for this event, 
 so I decided to provide this guide for anyone who intends to attend. I hope 
 you find this guide helpful, and remember to pack light. If you plan to 
 sleep at the school, there will be a lot of people in one big room, unless 
 you've reserved a room for a group. Of course, feel free to donate me some
 space if you're getting a hotel room.

 By the way, the above NAID logo was borrowed from the FILE_ID.DIZ of the
 naidtro.zip archive. I couldn't draw a logo of my own, and I liked that one 
 a lot, so there it is.

 Personally, I have never attended a demoparty, though I have some ideas on
 how to prepare for it, as I'm more familiar with Canada than I am with 
 Finland or Denmark. I'm hoping this guide can help everyone have the best
 possible time at NAID. This being the first party of this kind on this side 
 of the puddle, I would like to see the date go down in history, and the 
 party repeated in years to come. We need to show the Euros that we know how
 to party, too!

 Please keep in mind that this guide is intended merely as a complement to
 your regular luggage checklist. For your convenience, though, a small box 
 has been placed next to each item so you can check it off as you pack it. 
 Even though you now have this list, don't forget items like toothbrushes, 
 toothpaste, deodorant or anti-perspirant... Oh, hell with it. I'll probably 
 be the first to forget these items anyways. (Hope there's a drugstore in the 
 vicinity?)
  _
 |_| 1. First, you will need an English-French dictionary. As you know, 
     Quebec is the French-speaking region of Canada. Comment vas tu? Tu 
     habites aux Etats-Unis? Parlez-vous francais? Hmm. You might need to 
     work on your accent, too.
  _
 |_| 2. Next, you might want to take a life-jacket. Considering that a large 
     portion of you will be crossing the St. Lawrence River to get to the 
     school where NAID is being held, you don't want to take your chances 
     with those bridges. 
  _
 |_| 3. You will want to have a source of caffeine. Whether it be in the form 
     of money for soda machines or coffee, or your own beverage supply, it 
     will be required to stay up after hours and party, at which time you 
     will probably consume more caffeine, and party some more... and hell, 
     who really wants to sleep anyways?
  _
 |_| 4. Be sure to pack your teddy bear if you have one. Yeah, just look at 
     that poor little guy sitting on your bed. How do you think he feels when 
     you just leave him there?
  _
 |_| 5. Bring along unfinished programs and songs and such, and maybe you can 
     get together with someone else who has a pute and some knowledge, and 
     work on it with them. In fact, here's a C program that I started which I 
     need help with. If anyone can assist me, please let me know. (I just 
     recently took up C as a hobby, so please bear with me.)

 -----[cut]-----[blah.c]-----
 
 #include <stdio.h>             /*    Blah v1.0.0  */
                                /*      1/04/95    */
 void main()
 { printf("The program is now running.");
 }
 
 -----[cut]-----[blah.c]-----

 I'm not sure what this program is going to be used for, but I'm sure once
 it is completed it will be really cool. :)
  _
 |_| 6. If you bring your own computer to NAID, be sure to lock it up, if at 
     all possible. At other recent demoparties, especially The Party 94, 
     equipment was stolen or damaged. This only applies if you're not bringing 
     your kid brother's CoCo, in which case you should leave it out in plain 
     sight, and hope it gets stolen. Then, when the culprit is caught, 
     everyone can point and laugh, and this should prove to be a funny 
     experience, for all except one person. Hey, win some, lose some, right?
  _
 |_| 7. You might want your own roll of toilet paper. Hey, you never know... 
     I can imagine that it sucks to get stuck on the can without toilet paper. 
     Have you ever hobbled down the hall to your toilet paper supply with your 
     pants down? Uhh.. not that I ever have, I just don't imagine it being 
     something any of you would want to get stuck doing. Yeah, that's it.
  _
 |_| 8. If you have a flashlight, bring it with you. This can be used for 
     finding the bathroom in the middle of the night, or just for reading 
     porno magazines in your sleeping bag. For the latter option, this will 
     let everyone around you locate you, and you can then trade porno 
     magazines with each other. However, please keep in mind that I do not 
     read porno magazines, nor do I promote pornography. <cough>
  _
 |_| 9. If you have a beeper or pager, leave it home if possible. It would be 
     just plain annoying to be watching a demo when all of a sudden, someone's 
     beeper goes off, half the crowd turns to find the source of the noise, 
     and misses the best part of the demo. Though it would be funny to hear a 
     tune with such a sound in it, or even a phone ringing, and watch everyone 
     looking for it.
  _
 |_| 10. Keep a calculator with you and keep track of the exchange rate for 
     your currency. You don't want to get ripped off when buying stuff or 
     exchanging your money. And in the event you want to sell something, you 
     can rip them off if you do it right.
  _
 |_| 11. You might want to bring some homework with you. You'll most likely 
     be away from home all weekend, and you might have some extra time during 
     which you can study. Or if you're really lucky, your books will get 
     stolen and you won't bother going to class anymore.
  _
 |_| 12. Bring a portable radio. If you live somewhat far from Quebec, you can 
     occupy yourself by finding cool radio stations that you'll never be able 
     to hear again after Sunday. You'll also have something to look forward to 
     when NAID '96 is planned.
  _
 |_| 13. Two words: breath mints. :)
  _
 |_| 14. Grab a flat-head screwdriver to take with you. What for? I don't 
     know. Wait, hmm. Looks like I have run out of ideas for this list.
 
 I hope this guide becomes a part of your trip to NAID. Print it out, have it
 translated into french, sign language, and braille. Share this guide with 
 others planning to attend. Fax it, snail mail it, tape it to your forehead.
 Memorize it backwards. Also, If you have any additions to this above list, 
 please contact me at the email address below. Anyways, hope to see you there!
 
 GraveDigger [uuDW/CoRE]
 digger@freeside.scsd.k12.ny.us

.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,

 <<Editorial>>

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 Much response was generated by last week's humorous editorial entitled
 Codethink(School);.  This week, I take a U-turn from humorous to dramatic
 (hey, you can't expect me to be in the same mood every week).

 One small note: I will make frequent use of the pronoun "they" as being
 third-person singular.  It is incorrect grammatically to have a sentence
 such as "Ask someone a question and THEY will give you an answer".  The
 sentence should be "Ask someone a question and he or she will give you an
 answer".  However, I will be using "they" as in the above example rather
 than filling this editorial with "he/she" everywhere.  Enough said, let's
 go on...

_____General Protection Relationships

 re-la-tion-ship, noun 1. a connection, association, or involvement.

 Without exception, every one of us in the demo scene has two things in
 common: we interact with computers and we interact with humans.  In
 essence, we have relationships with both.  Under close inspection, these
 relationships can actually reveal an amazing amount about who we are as
 individuals and how successfully we deal with others in our lives.

 Ask a computer what the sum of two plus two is and it will tell you four.
 Ask a human the same question and they will probably raise their eyebrows
 and wonder which mediation you've been taking.  Ask that same person if
 they want to go and see a movie.  Mabey they're sick, or busy, or tired, or
 just don't want to.  If you're lucky they might even say "yes".  Ask a
 computer if it wants to run a program.  It might have difficulty, but that
 computer will die, trying to make you happy.

 If you think about it, a computer is your ultimate friend.  It never tells
 you to get some sleep or do your homework.  Its always there, waiting
 patiently for you to make a request.  With games, demos, and various GIFs,
 the computer can give you hours and hours of entertainment.  Even more,
 your computer actually changes with you: it remembers what you have done
 in the past and keeps track of what's new in your life.

 How many times have you had an argument with someone and gone to your room
 to watch Second Reality or play a game of DOOM?  In that respect, a
 computer can help relieve stress.  The computer is always in your corner,
 willing to help out with any problem you might have at the time.

 Over the years, I have had a lot of difficulty in forming lasting relation-
 ships with members of the opposite sex.  Part of this stems from my
 inability to correctly guess what they "mean" all of the time.  Say I ask
 woman X if she wants to go and eat at McDonalds.  The reply is "well...ok".
 Let's just take a few possible interpretations of this answer:
   1. "I am tired of eating at McDonalds, can't you think of anywhere else?"
   2. "I don't really care where we eat."
   3. "While I was saying the word 'well', I was actually trying to think
      of some place else we could eat.  I couldn't, so I guess McDonalds
      is 'ok'."
   4. "That was just a silly answer.  You know I always love to at at
      McDonalds!"
   5. "The only reason my answer came out like that was because I was
      watching the road for you to make a mistake while driving."
   6. "What?  Are you trying to tell me I'm FAT?"
 The list of guesses goes on and on.  A computer only HAS two answers,
 yes and no (1 and 0).  Its nice not having to play mind games once in a
 while.

 The computer is a shield between you and reality.  It can transport your
 mind away from the physical world; away from the problems, the headaches,
 the work, and the daily routines that we go through every day.  The more I
 think about it, I realize that our "Escape" CD was very appropriately
 named.

 As this article draws to a close, I begin to wonder if its any good or if I
 should just delete the whole thing and call it a day.  I just asked my
 computer if it likes the article and it wouldn't tell me.  Oddly enough, I
 feel like calling my parents right about now.

 -Christopher G. Mann / HORNET   January 29, 1995

.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,

 <<Code>>

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

_____Ctrl-Alt-Delete, Now Its a Game! by Denthor

 Telephone conversation :
 <Ring> <Ring>
 <Click>
 Fanus   : Hello, Buys residence.
 Denthor : Hi there Fanus, whats up? Can I speak to Piet?
 Fanus   : Ummm ... he's not in ... ummm ... who is this? I don't recognize
           you.
 Denthor : Don't worry, it must be my new haircut.
 Fanus   : Oh. This must be Denthor.

 Hi all! I am back after a two week absence from the Demuan List. Today I am
 going to introduce you to two new games, which should make sitting at the
 computer and listening to music a lot more fun.

 The first game is one I have described before in my trainers. It requires
 two people and a computer. I like to call it Control-Alt-Delete. Here is
 how it works. One person gets the delete button, and the other person gets
 the Control and Alt buttons. Player one must then hit delete very quickly,
 while player two has to try and hit control and alt at the same time. If
 the computer reboots, player two wins, otherwise player one stays at his
 station. When player one wins, they swap sides and begin again.

 This game can provide hours of enjoyment, and really is great fun in
 between really boring lectures about stuff you learned years ago. When I
 invented the game, I thought I was doing really badly against Pipsy until I
 realised that the computer had frozen.

 Note : People have caught on how to play at the local university, and sneak
 up and play it on my computer while I am telnetting. Be warned. Also, the
 game isn't as much of a challenge when you play it by yourself.

 The second game I invented while I was on holiday last week (one of the
 reasons I didn't write an article) ... we were down the South Coast, stuck
 in a hotel room while it poured with rain outside. The Tugela river
 overflowed it's banks, the sand bars dissapeared, and the tan I was hoping
 to get never appeared. (I have been programming so much I haven't seen the
 sun for the past three months, so when I finally get to go away, it rains,
 of course. Way to go, Murphy.)

 Anyway, with no computers, no phone, South African TV and no nightlife, we
 had no choice but to listen to the radio. After a while of mind numbing
 boredom, I invented a new game. I haven't named it yet, but here goes. You
 listen to a song on the radio. Every time the singer says a word that is
 more then one syllable long, you add a point. You don't count words twice,
 or all songs would get a high score.

 Most of the songs got between three and five, but we lost count when they
 played a Counting Crows song. Ace of Base did surprisingly well, wile some
 rap artists didn't score anything. Try it, you'll be amazed.

 The PC Games Programming Encyclopedia part two will be out on the 10th of
 Febuary, I will make sure that Hornet is one of the first sites to get it.
 I hope to have up to number 20 of my trainer series in it.

 So, I leave you to pick a game and start playing!

 Byeeeee...

 Denthor - denthor@beastie.cs.und.ac.za

 PS. This no-GUS thing is a Creative Labs conspiracy, isn't it?

................................................................continued...
DemoNews.081.continued.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.part.2.of.2

             SECTIONS          ARTICLES
             ----------------  -----------------------------------
             Code              Assembly Part 3 (It ain't no party)
                               BSP Trees
             Back Issues       How to Get 'em, Descriptions
             Closing Comments  Quote for the Week, etc.

.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,


_____Assembly Part 3 by Jason Nunn

     \\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
     \\\\\\\\[ "Implementation Techniques" - Assembly Part III
     \\\\\\\[[  By Jason Nunn
     \\\\\[[[[
     \\[[[[[[[
     ____________________________________________________________________

 In this issue I will be discussing the basic nuts and bolts on how to
 implement an assembly program geared towards a demo. This article is
 intended for the C or Pascal programmer who hasn't quite got the confidence
 to use a full blown assembly compiler. In the first part, you may remember
 me telling you of a friend that has reached a turning point in his coding
 development, yet he still won't "take the plunge" because he doesn't have
 access to all the nice perks of 3GL's, like sine, cosine, and random
 functions and larger precision variables than the chip itself. This issue
 will hopefully provide that incentive.

 But...., before we do that, I would like to first finish off last article's
 talk on optimization. I forgot to include the fast string functions. I'm
 not going to waffle on too much about this now, as this article is
 dedicated to "assembly techniques". All I will do here is show my results,
 and give out some tips.

 Same things apply on this run - my machine is a 486-33 ISA, operating in
 P-mode, and the lower the number, the faster a given instruction is.

         STOSB   [209729]                MOV     [EDI],AL   [134226]
                                         INC     EDI

         STOSD   [306805]                MOV     [EDI],EAX  [244208]
                                         INC     EDI

         LODSB   [209729]                MOV     AL,[ESI]   [134226]
                                         INC     ESI

         STOSD   [306805]                MOV     EAX,[ESI]  [244208]
                                         INC     ESI

         MOVSB   [228550]                MOV     AL,[ESI]   [142124]
                                         MOV     [EDI],AL
                                         INC     ESI
                                         INC     EDI

         MOVSD   [384379]                MOV     EAX,[ESI]  [324112]
                                         MOV     [EDI],EAX
                                         INC     ESI
                                         INC     EDI

 Of course, REP operations are faster than their equivalent by about half.
 In general, it is better to use MOV's and INC's to perform one off
 operations. So if you're coding with these instructions, chances are that
 you can get a bit more speed out of your code.

 Ok, now on with the main talk. Generally, I won't be going into great depth
 as there are plenty of tutorials and manuals on the net that explain the
 rank basics of assembly. My role here will be to highlight and familiarize
 extrordinary things about coding methods of assembly.

 If you've never coded in assembly, then it may pay you to write your
 equivalent program in a 3GL first and before converting it over. I guess it
 depends on the person. I prefer to implement idea's in straight assembler.
 I'm comfortable with the language enough to mumble it in my sleep and their
 are no barriers or contingencies like there are in 3GL code. You can also
 run into serious problems when converting to your target language, but I'm
 sure that there are as many negative points about doing this as they are
 positive points.

 How to crunch huge numbers
 --------------------------

 One of the first questions a new demo coder may ask is how he/she could
 add, multiply or subtract a number that is larger than the precision of the
 chip. Well, this really doesn't apply now, as the standard is 32 bits. This
 is ample for nearly all calculations, but for those of you that may want to
 perform a 64 bit ADD calculation, this is how you do it:

         ADD     EAX,ECX
         ADC     EDX,0

 In this example, we don't have a 64 bit register, therefore we must make
 two data sources, whether they be registers or memory references to act as
 one large register. In our case, EDX and EAX act as one. EAX contains the
 least significant data and the EDX contains the most significant data of
 our 64 bit number. ECX contains the number we are adding to this 64 bit
 concatenated register. The basic idea behind this is that we first add ECX
 to EAX. If the number in the EAX register "clocks" then the CPU's carry
 flag will be set.

 The next instruction - ADC (for those of you that don't know) is a funny
 sort of ADD instruction that performs two add instructions. It will first
 add the source register to the destination register, and then add 1 to the
 source register if the carry is set. Hence the name "ADD ON CARRY". In our
 example, if the carry flag is set, we will only add in the carry flag as
 the source value is zero. Therefore, if the least significant component of
 our 64 bit variable (EAX) clocks, the it will carry over to the EDX
 component.

 Although the above example only adds a 32 number to the 64 bit number. If
 you wanted to add a 64 bit number to a 64 number then you would adopt the
 following:

         ADD     EAX,ECX
         ADC     EDX,0
         ADD     EDX,EBX

 Where EDX:EAX is the destination 64 register, and EBX:ECX is the source
 register.

 To add larger precision's, we simply chain!. Here we are adding a 32 bit
 number that resides in EAX to a 128 bit number which is stored in
 EDX,EBX,ECX and ESI.

         ADD     EDX,EAX
         ADC     EBX,0
         ADC     ECX,0
         ADC     ESI,0

 To subtract, the same principle applies, accept we use SUB and SBB
 instructions:

         (a)                                     (b)
         SUB     EAX,ECX                         SUB     EAX,ECX
         SBB     EDX,0                           SBB     EDX
                                                 SUB     EDX,EBX

 With the 486's math coprocessor, the large multiplication and division is
 more viable than our old conventional way of calculating large numbers;
 which as you will see and very slow. Pretty soon, I will be exclusively
 using coprocessor calculations in my demos, as they are extremely popular
 now. Hence rendering the following code (for me) obsolete. However, for
 names sake, I'll discuss the old way of doing things...

 For multiplying a 64 bit variable to a 32 bit variable you can use this
 algorithm:

         MOV     EAX,ESI
         MUL     EBX
         PUSH    EAX EDX
         MOV     EAX,ESI
         MUL     ECX
         POP     ECX EBX
         ADD     ECX,EAX

 As a formula, the code is equivalent to this: ECX:EBX = ECX:EBX*ESI.

 Note that you can chain this one also by taking the EDX value from the
 second MUL and multiplying it by the next significant register of the
 source and adding that answer into the respective register of the
 destination.

 Dividing is a little bit more complex. How complex?...this complex:

         PROC LONG_DIV
           OR            EBP,EBX
           JZ            @@jump_0599
           PUSH          EBP
           MOV           EBP,ECX
           OR            EBX,EBX
           PUSHF
           JNS           @@jump_0548
           NOT           ECX
           NOT           EBX
           ADD           ECX,01
           ADC           EBX,00
         @@jump_0548:
           OR            EDX,EDX
           PUSHF
           JNS           @@jump_0557
           NOT           EAX
           NOT           EDX
           ADD           EAX,01
           ADC           EDX,00
         @@jump_0557:
           MOV           ESI,ECX
           MOV           EDI,EBX
           XOR           ECX,ECX
           XOR           EBX,EBX
           MOV           EBP,0021h
         @@jump_0562:
           RCL           ECX,1
           RCL           EBX,1
           SUB           ECX,ESI
           SBB           EBX,EDI
           JNB           @@jump_0570
           ADD           ECX,ESI
           ADC           EBX,EDI
         @@jump_0570:
           CMC
           RCL           EAX,1
           RCL           EDX,1
           DEC           EBP
           JNZ           @@jump_0562
           POPF
           JNS           @@jump_058A
           NOT           ECX
           NOT           EBX
           ADD           ECX,01
           ADC           EBX,00
           POPF
           JNS           @@jump_058D
           JMP           @@jump_0597
         @@jump_058A:
           POPF
           JNS           @@jump_0597
         @@jump_058D:
           NOT           EAX
           NOT           EDX
           ADD           EAX,0001
           ADC           EDX,00
         @@jump_0597:
           POP           EBP
         @@jump_0599:
           RET
         ENDP

 This formula divides EDX:EAX by EBX:ECX. Just in case anybody recognizes
 this thing, I've reversed it from a certain popular commercial package (not
 giving any names) hehe :). I havn't used it since my real mode days
 (which, for the record is about 2 years ago when coding TC669), and it's
 basically optimized for that. I've made no attempt to optimize it for
 P-mode, as I most likely will never use it ever again.

 How to implement a Decimal point (or rather - a hexadecimal point :)
 --------------------------------------------------------------------

 Now that we have discussed the ways in which we can do a whole range of
 calculations, your next question is how to implement floating/none discrete
 calculations. For that, we must take a register/memory unit and divide it
 into two parts. The number and a mantissa. For the sake of efficiency, you
 would typically contain this in a single register, namely a 32 bit
 register. I usually use this type of construct (represented in binary):

          /------------32 bits------------\
          NNNNNNNNNNNNNNNN.MMMMMMMMMMMMMMMM

 Here you have a 16 bit actual number, with a 16 bit mantissa. As you can
 see the actual number is of a higher order than normal. If to wanted to
 extract the number from this variable, you can simply perform a SHR 16.
 This will arrive you at the "NNN...." component of the number. Here is an
 example of 1 and a half:

         0000000000000001 1000000000000000b

 If we wanted the discrete part of the number (ie the "1" part), then just
 perform a SHR 16, which arrives us at: 0000000000000001. As you can see,
 there is no real difference between discrete and non-discrete variables. To
 the machine, it's all the same thing. The difference is the way you
 interpret the product. Calculations are still no different to normal
 numbers. If we wanted to add a "half" to this number then it's as simple
 that this:

    MOV     EAX,00000000000000010000000000000000b   ; this is a decimal "1"

    ADD     EAX,00000000000000001000000000000000b   ;this is a decimal "0.5"

 So, as you can see, it's not very hard. For multiplication, you're going to
 have to include a SHRD instruction, as the number will now be in EDX and
 the mantissa in EAX, hence the precision is now larger. This will return
 the number back to the EAX 32 bit precision that it should be. Here is an
 example:

         MUL             ECX
         SHRD            EDX,EAX,16

 Here, we multiply EAX by ECX, which arrives at EDX:EAX. Then we just step
 down this answer to arrive at the result, witch will now be contained in
 EAX. With division, it's the opposite:

         MOV             EDX,0
         SHLD            EDX,EAX,16
         DIV             ECX

 Here we are dividing EAX by ECX. Note the preparation just before the
 divide.

 Signed Data
 -----------

 As of now, we have only discussed unsigned data. Generally speaking, these
 calculations are very simular, but there are some major differences.

 Contained in a given 32 register, unsigned numbers go from 0 to FFFFFFFFh,
 where as 32 signed data range from 80000000h which is the lowest number and
 7FFFFFFFh begin the highest number. When using signed data, there are only
 a couple of extra things you must know. Signed data has its own
 multiplication and division instructions (ie IMUL and IDIV), and its own
 set of conditional jump instructions.

   JL (jump if less than) and JLE (jump if less than or equal to)
       are a signed equivalent to
   JB (jump if below)     and JBE (jump if below or equal to).

   JG (jump if greater)   and JGE (jump if greater than or equal to)
       are the signed equivalent to
   JA (jump if above)     and JAE (jump if above or equal to).

 To change our unsigned divider from this....
         MOV             EDX,0
         SHLD            EDX,EAX,16
         DIV             ECX

 ...To a signed divider, simply substitute the MOV EDX,0 with a CDQ. The CDQ
 extends a signed number in EAX into EDX. Example given:

         CDQ
         SHLD            EDX,EAX,16
         IDIV            ECX

 Implementing Complex mathematical relationships
 -----------------------------------------------

 At one time or another, a coder is going to have to use some sort of
 complex mathematical function like triangle ratios, logarithmic factors and
 random numbers to implement various things. To create a function that maps
 a relationship in real time is basically impossible in efficiently terms.
 The only way you can do this is to store relationships in the form of
 tables. This may not be apparent to users of compilers like turbo C etc but
 electronic calculators, compliers, maths coprocessors, spreadsheets all use
 this method of mapping these relationships. it a very fast a convenient way
 of doing things.

 The first common function is the random function. A random signal can be
 achieved using the following algorithm. The product of this function is a
 random number stored in the EAX register.

         ;input: NIL; output: EAX
         proc random
           mov  ebx,[random_seed1]
           lea  ebx,[ebx*4]
           mov  eax,[ebx+@@rantable]
           mov  ebx,[random_seed2]
           lea  ebx,[ebx*4]
           add  eax,[ebx+@@rantable]
           mov  [ebx+@@rantable],eax
           inc  [byte random_seed1]
           and  [byte random_seed1],01111b
           dec  [byte random_seed2]
           and  [byte random_seed2],01111b
           ret
         random_seed1
           dd    2
         random_seed2
           dd    13
         @@rantable:
           dd 0fd8fce7ah,02d7ad7b7h,0f48a8f3ab,04a3b8f8bh
           dd 0f2dec542h,0a847fab7h,0f4da81aab,04a348f86h
           dd 024547edah,03b535a43h,0b35a535ab,0aa333483h
           dd 0fd2f4e7ah,0c525a5b7h,016d3b4a4b,0643b4fd3h
         endp

 If you expand the table to 256 entries then you could eliminate two
 instructions, but there again, it's not worth doing. This random function
 will give you a very random signal :). There is only one problem with this
 algorithm, and that is, the randomness will always follow the same pattern.
 If this feature undesirable, then you may like to make an initiation module
 that jumbles up the seeds or the numbers a bit. An obvious way of randomly
 choosing a seed, would be to store a fixed reference variable in memory.
 For example:

         proc randomise
           mov  al,[043253445h]
           mov  [byte random_seed1],al
           mov  al,[012345678h]
           mov  [byte random_seed2],al
           ret
         endp

 Anyway, I'm going to stop here as it's getting very close the deadline
 time. One day, I'll learn not to leave things till last minute. In the next
 part, I'll be hopefully finishing up this assembly series and moving on to
 my talks of sound/tracker programming (the interesting stuff).

 I'll be soon releasing a tracker that I have written called FunkTracker.
 With this will be the full source code listing. My discussions will be
 based around my knowledge and experience when producing current and past
 trackers and players, and discussing implementation and hardware issues. I
 also plan to discuss reverse engineering using microsoft CodeView, and plan
 to obtain hack docs on the AWE32 card. So this will be all coming up!.
 until next time.

 See ya
 :Jason Nunn


_____BSP Trees by Tom Verbeure

 Problem situation: sorting polygons is slow and can be incorrect for
 certain view-angles. Heavily influenced by Computer Graphics, Principles
 and Practice, I have written this small tutorial for BSP trees, which
 solves the problem for static objects and for every view angle.

 As I already said: Binary Space Partitioning Tree. Unlike many other
 abbreviations, this one really explains a lot of the algorithm: it uses a
 tree. It partitions space and it partitions in two parts.

 First: it is only usefull in static scenes: no 3D morphing or other goodies
 are allowed.

 Let's go to the 2D case, 3D is exactly the same.
 Take a sample scene:

         A\        -----   C|
               \   B       E    |
           ------   |
                                |
                    /    .
                   /      V
                 D/

 The positive side of the polygons is the side with the defining
 character... Ignore V for now.

 One could sort this thing during rendering, but as there can be no correct
 sort criterium and sorting is slow, we don't want that. Besides, we have
 memory to spare :-)

 Now, we're going to build a tree that is totally viewpoint independent:

 Take polygon B as the root. Polygon B divides space in to parts: the
 positive and the negative side (Geee!) We have partitoned space in two.

 First, scrap B from the 'not-used' polygons-array and classify the
 remaining polygons. Group those on the + side, and those on the - side. As
 you can see, polygon C is both on the + and the - side. What to do? Create
 2 new polygons C+ and C-, erase C. Is there another complainer ? Nope: all
 poly's are on either the + or the - side. Now we have this situation:

                B
                               / \
                         A,C+,E    D,C-

 Not really a tree yet, but we've only started...

 Now, do the same thing for the groups at the child nodes, without caring
 about those in another child-node.

 For the + side of B, we have polys A,C+ and E. Take A as next node polygon.
 Neither C+ nor E are on it's negative side (we ignore D and C-). For the
 other node, take D as next node polygon. Only C- remains there, and it is
 on the negative side. That side of the tree is finished. We have the
 following situation:

                                B
                               / \
                              /   \
                             A     D
                              \     \
                             C+,E    C-

 There's one child with more that one poly left. Take C+ as node polygon, E
 become it's child, on the positive side. We're finished.
 Situation:

                                B
                               / \
                              /   \
                             A     D
                              \     \
                               C+    C-
                              /
                             E

 Now, what can we do with it? A lot... Suppose the viewpoint is at position
 V. In which order do we have to sort the polygons, when using a back to
 front rendering algorithm ? Answer: walk the tree, make sure all nodes
 (including childs) are visited.

 Start at the root. Is V on the positive side? Nope, well, we want the polys
 far away first, so walk the positive way. Are we on the positive side of A?
 Yep, walk the negative way. It is empty! Ah. Well, draw A first. The go the
 positive way. Are we positive of C+? Yep. Negative way of C+ is empty. Draw
 C+ poly. Go positive way of C+. E has no child, draw it. Go up until a
 non-empty branch is found, draw all node polygon not drawn already. We now
 arrive at B again. Draw it. Negative is not visited yet, walk it. We're
 negative of D. Positive way is empty. Draw D and go negative. C- has no
 child. Draw it. All nodes have been visited. The end.

 We have drawn the polygons in following order:

 A, C+, E, B, D, C- which is a correct order. The BSP tree has to be
 constructed only once and for all. From then on, sorting the polygons is
 always correct and in linear time. Standard sorting algorithms can be
 proved to be of n*log(n) order of time, so we have an increase in speed as
 well.

 Disadvantages:

 - Memory: one has to have the tree in memory. This can be substantial for
       lots of polygons.
 - Polygon splitting: one ends up with more split polygons. It is almost
       always unavoidable to do splitting.
 - Polygons are not allowed to move.

 A BSP tree is NOT unique: just pick another polygon as a node and one gets
 a different one. In this case, one can avoid splitting polygons: start with
 a root and build the following, correct, BSP tree:

                        C
                       /
                      B
                     / \
                    A   D
                   /
                  E

 Tadaam! No polygon splitting!

 Building a tree with a few splitting as possible is an exponential of the
 number of polygons. As Foley and Van Dam says, just try a limited number of
 nodepolygons, pick the one with the least splitting and the tree will be
 good enough.

 Voila. That's it. Not too difficult I think. Notice BSP trees are also
 usefull to sort objects, by using planes that divide the space in such a
 way that Object A is on the negative and Object B is on the positive side
 of the plane. Very useful (only for non-intersecting objects).

 This text is written without the Bible (Computer Graphics, P&P) besides me,
 but since I read their chapter about BSP trees many times, it contains
 almost the same info.

 For polygon splitting algorithmes, there is one in Graphics Gems. I don't
 know which one, but buy all four books, you won't be disappointed... :-)

 Tom Verbeure
 Synergy Design

.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,

 <<Back Issues>>

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 After reading this issue of DemoNews, you may be wondering how you can get
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_____Descriptions

Issue  Index  Date      Size    Description
-----  -----  --------  ------  ----------------------------------------------
  75   41,42  12/18/94   68009  A DemoNews Reader, The Birth of Commercial
                                Life, Editorial: Calm Before the Storm,
                                Interview with Mello-D, US Demo Scene
                                (Renaissance meeting), Jelly Tots and Pizza
                                Shops, Review of Wired '94 Graphics.

  76   43,44  12/25/94   92589  Interview with EMF, DemoNews Readers Write,
                                Kimba's Life Story, X-Mas in the Demo Scene,
                                CORE, Demo & Music Database, Interview with
                                Purple Motion/Future Crew, Interview with
                                Krystall/Astek, Common Sense ][ by Perisoft,
                                Its X-Mas in Africa, Interview with Maxwood
                                of Majic 12, Assembly Part ][, Common Sense
                                Response by Stony.

  77   45,46  01/01/95  101100  Chart History, Snowman Near-Disaster, Son of
                                Snowman, The Party 1994, Making Waves, Using
                                Assembly Part 2.

  78   47-49  01/08/95  111185  The Party 1994: Results and Reviews, Report
                                by Stony and Friends, What happened to PC-
                                Demo competition.  Editorial: TP94 = ASM94
                                part 2.  Egg2: Trancescrambled Review, More
                                on Fast Tracker 2.03.  General Rambling by
                                Denthor.

  79   51     01/15/95   41832  A Day in the Life of Snowman, Ambient Sample
                                CD 1, Where's the Sound Blaster, TP94
                                Graphics review.

  80   55     01/22/95   27028  DemoNews/HTML, Traffic Jam, CodeThink(School);
                                The Solo Sample CD

.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,

 <<Closing Comments>>

''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''

 The quote this week comes from "Assembly Language for the PC, Third
 Edition". p.174

    "A program is never done...but it must be stopped somewhere."

 This was intended as a moral for programmers, but with a little rewording
 the message is applicable to many areas in life.

 See you in CyberSpace,

                        -Christopher G. Mann (Snowman)-
                            r3cgm@dax.cc.uakron.edu

,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,End.of.DemoNews.081.

