Development of Doom

Conception
Following the successful release of Wolfenstein 3D in May 1992, most of the id Software team worked on the sequel, Spear of Destiny. Since this game used the same engine as Wolfenstein, lead programmer John Carmack could use the time to begin work on the company's next-generation graphics engine. With significant effort, choosing to isolate himself from the rest of the team for a long period of time in order to avoid distractions, he implemented various new features, including varying light levels and texture-mapped floors and ceilings. He even added support for sloping floors, although this feature was later removed. The engine was not developed with Doom in mind, and in fact Doom was not the first game to make use of it: Raven Software licensed an early version for Shadowcaster, which would be published some months before Doom.

After the release of Spear in September 1992, development began in earnest. The initial idea was to make a licensed game based on Aliens, one of the team's favorite science fiction-action films, and some negotiations were conducted with 20th Century Fox. This plan was eventually abandoned in order to get more creative freedom. John Carmack instead conceived of the basic theme for the game: demons versus technology. Doom was then imagined as a cross between Aliens and the team's favorite B-grade horror movie, Evil Dead II. The idea to include demons was also inspired by their most recent Dungeons & Dragons campaign, which had ended with demons overrunning an entire planet.

Tom Hall and the Doom Bible
The horror-tech theme was not accepted unanimously. Creative director Tom Hall had instead wanted to continue the Commander Keen series with a third trilogy, but the others felt that the cartoon style of the Keen games would not do justice to the new 3D engine. Conceding defeat, Hall set out to create the new game's design document, which he titled the Doom Bible, while the others were programming and creating graphics.

Unlike Wolfenstein 3D, which had essentially been a plotless shooter game, Hall wanted Doom to have an elaborate story. The game was to take place on an alien planet called Tei Tenga, on which the UAAF (United Aerospace Armed Forces) had two military research bases. There would be five player characters with different personalities and abilities: Lorelei Chen, John "Petro" Pietrovich, Dimitri Paramo, Thi Barrett, and Buddy Dacote; the game would start with creatures from Hell suddenly bursting in while the five were playing cards. There would be a total of six episodes, with storylines involving traveling to Hell and back through the gates which the hellspawn used, and the destruction of Tei Tenga, for which the players would be sent to jail.

John Carmack disapproved of the detailed plot, instead imagining Doom as a simple, action-oriented game. He remarked, "Story in a game is like story in a porn movie. It's expected to be there, but it's not that important." This creative conflict ended with the others agreeing that Hall's levels emphasized realism at the cost of making the gameplay entertaining. Hall was forced to resign in the summer of 1993.

The Doom Bible as such was scrapped, but several of the ideas were kept for the final game. As in the Bible, Doom starts in a military research base and features a trip to Hell and back, although Tei Tenga was replaced with Phobos and Deimos, the moons of Mars. Several of the locations, items and monsters mentioned in the Bible appear, though modified.

Some concepts from the Doom Bible, though discarded for Doom, made their way into later titles:


 * Instead of employing separate levels, Doom was initially supposed to use a "hub" system to enable a large, continuous world: the different areas would be connected by a monorail. Hubs were later used in Hexen and in id Software's Quake II, and a monorail featured prominently in Doom 3.
 * The Doom Bible originally included interactive computer terminals; these first appeared in Doom 3.
 * The "Laser Gun" from the Doom Bible later became the Unmaker in Doom 64.
 * Tom Hall used concepts from the Doom Bible in Rise of the Triad and Terminal Velocity, which he designed after leaving id Software for Apogee and 3D Realms.

Programming
Doom was developed on NeXT workstations, under the NeXTSTEP operating system. The final game engine was programmed in C, and the editing tools were written in Objective-C. The engine was first compiled with Intel's C compiler for DOS, but later Watcom's compiler was used.

The bulk of the engine was programmed by John Carmack. John Romero implemented code for saving and loading games, as well as interactive features such as flickering lights, doors, rising stairs, and crushing ceilings. Dave D. Taylor was hired as a "spackle coder", adding such things as the status bar, sound library integration, the automap, level transitions, cheat codes, and the network chat system. The sound library, DMX, was an external piece of software created by Paul Radek, and not included in the 1997 release of the Doom source code.

The editing tools used to build the game included scripts to generate source code for monsters from definition tables, a tool to piece together WAD files from data lumps, the BSP node builder by John Carmack, and DoomEd, the level editor. DoomEd's structure and basic functionality, such as drawing lines and reading sector information, was implemented by Carmack; Romero added texture viewers and dialogs. Among these utilities, only the BSP node builder has been released to the public.

Levels

 * Main article: Levels

The Doom Bible contained detailed descriptions of scenarios that were to appear in the game. Tom Hall studied real military bases to create realistic locations, such as "Recreation and Training Center" and "Supply Depot Two". He designed several levels, but as they were constructed and placed in the game, the others found them banal and uninspiring. Hall's levels were mostly flat and square, like Wolfenstein 3D, and decorated with real-life wallpapers, floor tiles and office equipment. To show off the game engine's capabilities, John Romero instead began creating levels that were more abstract. The team settled on Romero's less realistic but more vivid style, which is found throughout the game's first episode, Knee-Deep in the Dead.

Romero only designed the levels for the first episode, being occupied with programming and other tasks. When Tom Hall resigned, an extra level designer was needed in order to complete the game on schedule, and Sandy Petersen was hired about 10 weeks before release. In those 10 weeks, Petersen completed all of the second and third episodes, and one level for the first episode — 19 levels in total, of which eight were overhauled versions of levels by Tom Hall. Petersen paid less attention to aesthetics than did Romero, but the others thought his levels were as fun to play.

Graphics
Adrian Carmack and Kevin Cloud were the chief artists behind Doom. Additionally, Don Ivan Punchatz was hired to create the package art and logo, and his son Gregor Punchatz designed some of the monsters.

Most of the sprites were drawn by hand, but some of the characters were digitized from sculptures. These were the player character, the Cyberdemon, and the Baron of Hell, all done in clay by Adrian Carmack, and the Arch-Vile, the Mancubus, the Spider Mastermind, and the Revenant, created in latex and metal by Gregor Punchatz. The sculptures were photographed from four to eight different angles so that they could be rotated realistically in-game, and finally touched up, colored and animated digitally with a program created by John Carmack, the "Fuzzy Pumper Palette Shop".

The shotgun and the pistol seen in the game are photographs of toy weapons bought at Toys "Я" Us; the chainsaw is a McCulloch Eager Beaver, borrowed from Tom Hall's girlfriend. The hands seen holding the weapons, and the brass-knuckled fist, are Kevin Cloud's. Textures were both painted and created from scanned pictures. Among the more unusual sources, one texture was based on Adrian's snakeskin boots, and a bloody texture for the hellish levels was created from a photograph of a wound on Cloud's knee.

Sound

 * Main article: Sound

For music and sound effects, id Software hired Bobby Prince, who had previously scored Wolfenstein 3D and worked on the Commander Keen games. Initially, John Romero gave him several heavy metal records and told him to create something similar for Doom. As the design of the game progressed, it was realized that this style would not be appropriate for all levels, so Prince also created some ambient tracks. The music tracks were finally assigned to the individual levels by Romero.

Several of the music tracks are covers of songs by famous heavy metal bands. Although the covers were done without permission, none of the bands has attempted to bring legal action against id Software. According to Romero, Prince, who was previously a lawyer, "knew the legal amount of sampling that he could do without getting into trouble".

In addition to heavy metal albums, several of the songs were inspired by the activities of the id Software team. Prince and John Carmack would often stay in the office at hours when no one else was around; "Deep Into The Code" (E3M3 of Doom) refers to Carmack's habit of programming for long periods without leaving the computer, oblivious to his surroundings. Before sound effects had been added to the game, Romero was known for energetically supplying his own while playing, and Prince created the track "Waiting For Romero To Play" (MAP18 of Doom II) after observing the anticipation of people lining up to watch Romero in action. The final sound effects for the monsters were mixed from various animal sounds and recordings by Romero and Prince. Some of Doom's sound effects were acquired from Sound Ideas' General series sound effects library.

Pre-release versions

 * Main article: Alpha

Four pre-release versions of Doom originally intended for testers and the press have afterwards been released to the public due to historical interest. None of these versions have sound or music.