Cheating

     Unfortunately, cheating has always been present in almost every type of human competition.  DOOM is no different.  There have been some infamous instances of cheating in DOOM.  Note that it is very rare that casual DOOMers will cheat; as with these incidents, these players were already highly-skilled, accomplished players.  The demos that they recorded, in many instances, couldn't have been managed by an average player.  Other than some ruffled feathers in deathmatch games in the past and present, I don't think anyone feels any animosity towards these individuals.

     As the first wave of truly skilled single-player DOOMers competed for Compet-N points, Uwe Girlich was decompiling DOOM for his LMP Description and LMPC work.  Mr.Girlich and his friend, Steffan Winterfeldt, were already skillful players who played regularly for the Compet-N.  There were many holes in the points tables and lots of unexplored achievements that had yet to be reached.  Their quest to reach these goals would provide one of the Compet-N's worst moments and one of its best.
     No one knows for sure exactly how they cheated, but it is likely that they reverse-engineered the executable and exploited the fact that DOOM only records your movements in the demo lump.  Definitely playing in slow-motion and savegames, Girlich and Winterfeldt quickly recorded some amazing demos and started to push the limits of what most players thought possible.  In May 1996, Mr.Winterfeldt posted one of the most-watched demos ever, 30nm6520.  Fortunately, most of their demos have visual evidence of cheating, but since it is technically impossible to unequivocally detect a cheated recording, all of their demos have been removed from the Compet-N.
     In early 1996, there was a big push to achieve a 30-level nightmare run of DOOM2.  Originally deemed impossible, this feat would quickly be considered the ultimate achievement for a DOOM player.  Thomas 'Panter' Pilger, Frank "Jesus" Siebers, Peo Sjoblom, Daniel "Demonlord' Lindgren, Andreas 'Anthe' Kren, Steffan Winterfeldt, and Istvan Pataki were showing the true friendly spirit and competitive nature of the Compet-N by working together to make the feat part of history.  Kren reached Map15.  This is one of my favorite demos, his struggle here is epic.  One must understand that the routes used at this time were much slower than today.  It could be argued that the early incomplete Nightmare recordings took as much skill as the finished lightning demos of present day.  Winterfeldt reached Map21.  Using Winterfeldt's routes, Lindren reached Map21.  Then, Winterfeldt uploaded 30nm6520.   For quite awhile it was accepted as an authentic recording.   By the end of 1996, this demo was widely considered to be assisted and it was removed from the tables.   Frank Siebers found a new passion for 30nm and his Nightmare Movies page chronicled their endeavors. Pataki joined Lindgren at Map21.  Kren finally conquered Map22 but promptly died on 23.  Nm30 was proving to be a hurdle perhaps too high to be surpassed.
      In 1997, Thomas 'Panter' Pilger spread throughout the Compet-N tables like a plague.  By August, he was the first to do the third DOOM2 episode(Map21-30) on nightmare skill and was primed for the ultimate DOOM2 honor, DOOM2 Schwarzenegger.  Almost a year in the making, Thomas 'Panter' Pilger finally achieved the impossible by recording all 32 maps of DOOM2 on 'Nightmare!' skill in one demo in 49:49.  Pushing the other players to unassistedly achieve new records would become Winterfeldt's legacy, and for that, we are grateful.

     Andy 'Aurican' Kempling was the only other person to have demos removed from the Compet-N tables for recording with demo assistance(to my knowledge).  Kempling used a modified executable that was developed from the source ports of DOOM.  His offense was not nearly as invasive as Girlich and Winterfeldt but the controversy was just as high.

     There have been many different types of cheating in multiplayer games.  Using hacked maps, aiming enhancements, modified sounds and sprites, there are so many ways to cheat in DOOM multiplayer.  Bahdko's Cheating Explained page is a great resource on this topic.

Appendices:

Windows-compatible Source Ports of DOOM:
PrBoom -- PrBoom2.2.4 - Full support for playback and recording Boom, MBF, or even the real game.  The best way to play and watch DOOM on a win32 platform.
Eternity -- Eternity3.3.1 - Full support for playback of doom(2).exe demos.
Zdoom -- Zdoom1.22 - good demo support but only with Zdoom1.22 demos.
Legacy -- Legacy1.41 - good demo support but only with Legacy1.4 demos.
Jdoom -- Doomsday Engine1.7.14 - good demo support but only with Jdoom demos.

     Additionally, with the source released, there are many new features in the ports for demo recording and playback.  Deathmatch up to 16 players(maybe more than that now, I can't keep up :), Opengl support, cross-platform support, split-screen multiplayer, true 3D, sloped floors, skyboxes, mp3 support, client/server TCP multiplayer, etc....  the list is very long.  For demos, there is chasecam, flycam, recam, and even fast-forward and rewind!  Lots of miscellaneous features too; for example, with PrBoom, pressing  'F12' during a multiplayer game will completely change the point-of-view, sounds, and HUD to the next player.

Some miscellaneous facts:

• Moving forward + run + strafe_left + strafe_on + turn_left makes you move about 580 units per second.
• Moving forward + run + strafe_left + strafe_on + turn_left is roughly 141.4% of normal running speed(this is about the same as -turbo 130) and forward + run + strafe_left is roughly 128.1% of normal running speed.
• That Archviles will attack other Archviles; barrels do up to 128 points of damage; almost all the weapons, from monsters or players, do a variable amount of damage.
• The messages during a multiplayer game, the chat mode, do not appear in the demo lump when replayed.
• You can switch-exit a map when dead.
• If you record a savegame during a demo, it will record the savegame again when played back.

• Since DOOM is built on the polar coordinate system, the player can go faster if travelling on an axis of this coordinate system than normally. (same type of thing occurs in Quake with vectors or any similar game with chording/curling/circle-jumping)
• Because of this polar coordinate system, occasionally, the player (who is 33 units wide) can fit through a 32-unit wide diagonal opening.
• DOOM is only 2 and 1/2 dimensions (that is, the third dimension is faked; no two items can be in the same spot on the z-axis).  This allows for infinitely tall walls.  For example, you can switch a switch when it looks far above your head.
• Due to these limits of the z-axis, this also allows for the player to grab items at distances that should be too far away... even through walls!
• Moving at the fastest speed(with enough room to run up to accelerate to that speed) will allow the player to "jump" 194 units distance.
• Blast vector of weapon damage pushes the player to a speed faster than manually possible.  see also: Archvile jump.  see also: Cyberdemon rocket.  see also: fx's SSG.

Contributions/Credits: Doug Merrill, Andy Olivera, Laura Herrmann, Adam Williamson, Anders Johnsen, Fodders, and Adam Hegyi.
Thanks to Doomworld and Telefragged for enriching the lives of DOOMers everywhere.