Before id: the Softdisk years
John Carmack, John Romero, Adrian Carmack (no relation), and Tom Hall met while working at Softdisk, a subscription software company based in Shreveport, Louisiana. Softdisk published monthly floppy disks of software — a model that predated the internet as a distribution channel and gave its programmers a relentless production schedule. The team worked on games for the company's Gamer's Edge subscription service, producing competent work under tight deadlines in an environment that valued speed over ambition.
The break came when John Carmack, in his spare time, solved a problem that Nintendo's lawyers had argued was impossible: smooth, fast side-scrolling on a PC. The NES had dedicated hardware for horizontal scrolling. PCs in 1990 did not. Carmack's adaptive tile refresh technique — drawing only the changed portion of the screen rather than redrawing the entire frame — produced scrolling that matched the NES. The team built an unlicensed port of Super Mario Bros. 3's first level over a weekend to demonstrate the technology. They sent it to Nintendo. Nintendo didn't respond. The team decided to use the technology themselves.
They founded id Software in 1991. Commander Keen — a platformer built on Carmack's scrolling engine — launched via the shareware model in December 1990, before the company was formally incorporated. The first episode was free. Additional episodes cost $30 by mail order. Commander Keen sold well enough to fund the company's next project. The next project was Wolfenstein 3D.
Wolfenstein 3D and what it proved
Wolfenstein 3D (1992) was not the first game with a first-person perspective, and id Software knew it. Maze War (1974) had a first-person view. MIDI Maze (1987) allowed networked first-person play. Ultima Underworld (1992), released two months before Wolfenstein, had a genuine 3D engine with texture mapping and level geometry more sophisticated than Wolfenstein's. What Wolfenstein 3D had that none of its predecessors had was speed.
Carmack's raycasting engine — which rendered the world by casting rays from the player's position and calculating wall distances rather than managing full 3D geometry — ran at a frame rate that made movement feel immediate and continuous. Wolfenstein was not technically superior to Ultima Underworld, but it was viscerally faster, and visceral speed was what defined the experience. Players moved through the castle at a pace that no previous game had matched. Enemies fell with satisfying weight. The sound of machine guns in enclosed corridors communicated through the PC speaker in ways that felt aggressive and immediate. The game sold 100,000 copies in its first two weeks through the shareware model.
The shareware model that id used for Wolfenstein established a pattern they would use for Doom and Quake: the first episode (typically six to nine levels) was distributed freely on floppy disks, uploaded to bulletin board systems, and included on magazine cover disks in Europe. Players who wanted more had to purchase. The model relied on the first episode being good enough to sell the remainder, which meant the beginning of each id game received disproportionate design attention. It also meant the games reached players who would never have found them through traditional retail distribution.
Doom
Doom released on December 10, 1993, uploaded to a University of Wisconsin FTP server at midnight. The server crashed within hours from the volume of download requests. Students were calling their university's system administrators at home to complain that Doom was preventing them from using the network. A memo at Intel circulated the following week asking employees to stop playing Doom at work. Doom was installed on more computers in 1994 than Microsoft's Windows 95 would be installed on in its first year. These comparisons are rough, but they reflect something real about the scale and speed of Doom's spread.
What Doom did technically went beyond Wolfenstein's raycasting. Carmack's new engine supported variable floor and ceiling heights, non-orthogonal walls, outdoor areas with sky textures, and light sourcing that varied by sector. The levels were genuinely three-dimensional in the sense that they felt architectural rather than corridorial. The monster AI — rudimentary by later standards — was sufficient to create moments of surprise and tactical pressure. The networked multiplayer, connecting up to four players over local area networks, introduced most players to the experience of shooting at another human being in a shared space. id called this mode "deathmatch," a word they coined.
Doom also shipped with the ability to add user-made content — levels, graphics, sounds — through a format id called WADs (Where's All the Data). This was a deliberate design decision. Romero in particular believed that releasing the tools to modify the game would extend its lifespan and create a community of players invested in its world. The modding scene that Doom generated — thousands of user-made levels, total conversion mods that replaced the entire game, eventually commercial games built on Doom's engine — established the modding community as a feature of PC game culture.
The engine business
After Doom, id began licensing its engine technology to other developers. Raven Software used a modified Doom engine to make Heretic (1994) and Hexen (1995). Bungie licensed a version for Mac. The Quake engine (1996) — which moved from raycasting to genuine polygon-based 3D rendering — was licensed to Valve for Half-Life (1998), to Raven for Quake mission packs, and to numerous other studios. The engine licensing business that id established almost accidentally became a significant industry in its own right.
The concept was straightforward: the technology required to build a competitive game engine in the mid-1990s required expertise and time that most developers didn't have. Carmack's engines were better than what most studios could build internally. Licensing them was cheaper than building from scratch. id received licensing fees and a degree of credibility as the underlying technology of multiple successful games. Studios received an engine proven in commercial releases with known performance characteristics.
Epic Games — watching the same market — licensed their Unreal engine (1998) on similar terms and built a business around engine technology that eventually eclipsed id's. The Unreal Engine is now the dominant licensed game engine in the industry, used in film and television production as well as games. The business model that id Software invented by licensing the Doom and Quake engines to other studios is now a multi-billion dollar industry segment. Carmack didn't patent the approach and didn't build a company structure around it. He was more interested in the next engine than the revenue from the last one.