The development of Doom
article by Lord FlatHead

What many people (including some of the hardcore Doom fans) don't know, is that the original Doom was not always the perfectly balanced, polished game we know it to be. Doom was produced by id Software between 1992 and 1994, and underwent a few major changes to both the technology and the gameplay during its development. This article will take a look at some of the early material left from those golden days of game development.

Aliens ?

After id had finished the classic Wolfenstein 3D in mid 1992, it was time to start thinking of a new game concept. On 18th September 1992, after Wolf3D sequel Spear of Destiny had shipped, game designers John Romero and Tom Hall sat down to discuss what was going to be done with the new 3D engine John Carmack had been working on.

At first, id thought about acquiring the rights to do a game based on the Aliens movie series, but then decided not to because they wanted total creative control that they couldn't get with a movie license. So basically Carmack decided to change the aliens into hellspawn and end up with a game that was something new, yet kept the tense atmosphere and tech style of the Aliens movies.

To quote John Carmack, "Thematically, DOOM was viewed as Aliens meets Evil Dead 2."

The DOOM Bible
By late 1992, Tom Hall and John Romero had written up an 80-page design document called the DOOM Bible (which can be downloaded in PDF format here). Although very little of the detailed ideas in the document made it into Doom, it is quite an interesting read. Here are a few interesting things to note:
As you will see below, a few of these ideas showed up in the Alpha versions before they got cut. Others made it into Rise of the Triad (ROTT), a game Tom Hall did for Apogee after he left id.

  Alpha version 0.2 - February 1993 (By the way, all the alpha versions can be downloaded here)
This is a very early version of the Doom engine. The game itself had only been in development for two months, though it shows a few of the monsters and textures already that would make it into the full game.

As you can see, the game was originally titled "Doom: Evil Unleashed". The major thing to note about this alpha is the HUD - the ingame shot on the right shows a view of the world trough the Doom marine's helmet, complete with computer readouts and a map. The 0.2 alpha had only one little map, a few monsters (that stand around and do nothing) and a non-functioning shotgun. Also, like all of the other alphas, it does not have sound.

  Alpha version 0.4 - April 1993
A lot of improvement here. 0.4 features 13 full-blown maps, including a lot of areas that made it into Doom in some way. The shotgun has changed, the weird HUD is gone and the monsters can be shot (though they don't have death animations).
In the shot on the right you can see one of your (non-interactive) buddies mentioned in the Doom Bible, and some cards on a table. You can also see a few chair sprites that didn't make it into the game.
Here's a side by side comparison of a shot from alpha 0.4 (on the left) and from Doom's E2M1 (on the right). It clearly shows how the id designers had to learn to use the freedom provided by Carmack's engine, and to push their creative bounds away from the flat, blocky worlds they had been designing for Wolfenstein 3D. Here's another one :
Here you can see how the start area of what became E1M7 transformed from a flat, dull-grey backdrop into a more believable environment in Doom.
And finally, a shot showing the progress on the opening area of E1M2. To quote John Romero, who made a few of the above maps :

"When we started designing maps for DOOM, we were still in Wolfenstein 3D mode -- 90 degree square blocks and consistent lighting for the levels.  But as we started being more creative with the editor and exploring all the things we could do with the engine, then we started designing more interesting levels.  The alpha versions of DOOM that were released showed our map designing skills still in the Wolf3D mode, while later Beta version showed how far we were stretching."

  Alpha version 0.5 - May 1993
This version has another 13 maps (some of which are developed off 0.4 maps) and quite a few areas that made it into Doom. The map designers are really comfortable with the tools now, and the design is getting very close to Shareware Doom quality. The menu is also shaping up, even with some things that didn't make it into the game like in-game controls configuration.
Press Release Beta - October 1993
This beta dates from two months before the release of Shareware Doom, and there really aren't many differences between these two except for: The press release beta contains near-finished versions of E1M2, E2M1 and E3M5.
So that's the story of how Doom transformed from an incohesive buggy Wolf3D-clone into one of the most technologically ground-breaking computer games ever. We'll see in a few months if id can repeat this achievement...