John Carmack

The room begins to move

Carmack, Romero, Hall and Adrian Carmack founded id Software on 1 February 1991. Wolfenstein 3D, published through Apogee in 1992, put the player inside a room instead of above it, and id’s released source shows how little the engine had to draw to do so. The map is a grid of square tiles. For each column of the screen, an assembly routine steps a ray across that grid, testing only the points where it crosses vertical and horizontal grid lines, until it strikes a wall. The C function CalcHeight then measures the hit along the direction the player faces, which keeps walls from bulging like a fisheye lens, and a single division turns that distance into the height of one vertical strip of wall texture. Floors and ceilings are not calculated at all; the view is cleared to two flat colours. What the player feels is speed: rooms that swing past as fast as you can turn, with every wall the same height and every floor flat, because the grid allowed nothing else.

Doom, released in December 1993, broke the grid. Its levels are drawn as lines of any length and angle enclosing sectors, each with its own floor height, ceiling height and light level. A binary space partition tree, built when a map is compiled, lets the renderer walk the world from nearest to farthest; the released r_bsp.c keeps a short list of screen columns already covered by solid wall and ignores anything hidden behind them. Floors and ceilings are whatever remains in the gaps, collected into “visplanes” (the source comment calls it “the obnoxious visplane”) and filled as horizontal spans. Carmack’s 1997 README names the core idea: walls are vertical lines and floors horizontal lines “of constant Z”, so each line needs only one depth and one light level. On screen that bought stairs, lifts, pools of darkness and windows across courtyards. It also meant that no room could sit above another, because the map is still a floor plan.

Doom was a team’s game. Its credits list Romero, Hall and Sandy Petersen for design; Carmack, Romero and Dave Taylor for programming; Adrian Carmack and Kevin Cloud for art; and Robert Prince for music. Hall, whose designs had repeatedly been set aside and who had clashed with Carmack over gameplay, was dismissed by the other founders in July 1993, and Petersen arrived about ten weeks before release. id gave away the first episode as shareware and sold the rest, so the engine reached players through free copies passed along on disk and online.

An engine becomes a shared instrument

For Quake (1996) Carmack wanted true three dimensions: rooms over rooms, slopes, arches, and monsters built as models rather than flat pictures. Michael Abrash, who joined id in March 1995 and later wrote the work up in his Graphics Programming Black Book, records how many ways Carmack tried to decide what was visible. The design that shipped came, in Abrash’s account, after a weekend of work and a thought at 3:30 on a Monday morning: precompute, for every leaf of the map’s BSP tree, which other leaves could ever be seen from it. Stored as one bit per leaf and compressed, this potentially visible set fell to about 20 KB for a good-sized level. Abrash describes the effect on screen: complex scenes stopped being much slower than simple ones, and a spot where the frame rate had sunk into single digits now turned smoothly. Carmack, he adds, denied any “Eureka!” moment and called it a logical evolution.

Lighting was moved out of the frame too. The level compiler casts light onto a grid on every surface, one value every 16 texels; at run time Quake combines that light map with the tiled texture into a lit “surface”, caches it, and reuses it while it stays in view. Mipmapping kept that cache to about 600 KB at 320×200. The player sees soft-edged shadows and torchlight that stays fixed to the walls as the view turns. Abrash credits the shadow-edge filtering to a suggestion by Billy Zelsnack. Around the engine were programmers Abrash and John Cash; designers Romero, Petersen, American McGee and Tim Willits; artists Adrian Carmack, Kevin Cloud and Paul Steed; and Trent Reznor and Nine Inch Nails for sound.

Quake’s production was hard, and it ended the original partnership. Creative differences with Romero ran through the project and contributed to his departure after it shipped. On 8 August 1996 Carmack’s public .plan file said only: “Romero is now gone from id.” Six days earlier he had published his plan for QuakeWorld, admitting that he had designed Quake’s networking for connections under 200 milliseconds while most players dialled in through modems at 300 ms or worse. His answer was client-side prediction: the player’s own machine guesses the result of each movement, while “the server is still the final word.” He was frank about the cost. You would seem to run closer to doors before they opened, and shots could leave from where you had been rather than where you were. QuakeWorld was released in December 1996; it is a compromise players of later online shooters will recognise.

The Quake II (1997) and Quake III Arena (1999) engines were licensed to other studios, so Carmack’s choices shaped games he never worked on. id also opened its old code. Doom’s source arrived in December 1997 with a README in which Carmack lists what he would now change (“using polar coordinates for clipping comes to mind”). Quake followed under the GPL in 1999, a licence chosen, its readme explains, because mod teams had kept improved versions closed and sometimes lost them; by Christmas 1999 Carmack was answering complaints that players were using the code to cheat. Doom 3 (2004) reversed the bargain of the 1990s. Instead of baking light in advance, its renderer, released in 2011, fills the depth buffer first and then draws surfaces once for each light, masking shadows with the stencil buffer, on separate code paths for several generations of graphics card. That is the game’s darkness: lights that move, and shadows that move with them.

Away from id, Carmack funded Armadillo Aerospace from about 2000 and took the same build, test and change loop to rocket vehicles with a small team. NASA’s Lunar Lander Challenge asked for a vehicle to take off, fly sideways, land on another pad and return, all inside two hours and fifteen minutes. Armadillo won the $350,000 Level 1 prize in 2008 and in 2009 was the first team to qualify for the harder Level 2, finishing second, for $500,000, behind Masten Space Systems’ more accurate landings. ZeniMax, Bethesda’s parent company, bought id in June 2009, and Carmack stayed on as technical director.

Beyond the flat screen

In February 2013, still at id, Carmack published “Latency Mitigation Strategies”, an essay about head-mounted displays. His target was 20 milliseconds from a movement of the head to the light reaching the eye; typical VR systems, he wrote, had end-to-end latencies of over 100. He walked through the whole pipeline (sensor sampling, buffered GPU frames, slow display switching) and proposed remedies such as time warping: after a frame is rendered, shift it using the very latest head orientation, which corrects turning well though sideways movement smears. In August 2013 he became chief technology officer of Oculus VR. In November he left id altogether; its studio director said Carmack wanted to focus on things other than game development.

The clearest product of that work was mobile VR. Oculus’s September 2014 announcement of the Samsung Gear VR Innovator Edition says Carmack and the mobile team spent about a year reworking Android and the phone’s GPU drivers: unbuffered display surfaces, prioritised GPU rendering so asynchronous time warp could run, and a low-persistence display mode, bringing motion-to-photons latency under 20 ms on a phone. Carmack told Engadget that Samsung was sceptical until he hacked a prototype phone to draw straight to the screen, cutting two frames of delay. For the wearer the payoff was physical: the world held still when the head turned.

The move also brought a lawsuit. ZeniMax sued Oculus, alleging misuse of technology Carmack had developed while at id. In February 2017 a Dallas jury rejected the claim of trade-secret misappropriation but found breach of a non-disclosure agreement, copyright infringement and false designation, with $500 million in damages against Oculus, co-founder Palmer Luckey and former chief executive Brendan Iribe. ZeniMax’s lawyers also reported that Carmack was found liable for conversion; the damages they listed were assessed against the others. In June 2018 the judge struck the $250 million awarded for false designation and left $250 million for breach of contract and copyright infringement. The parties settled on undisclosed terms in December 2018.

In November 2019 Carmack stepped back to a “consulting CTO” role to work on artificial general intelligence. He left Meta in December 2022 with an internal note, later posted publicly, that called it “the end of my decade in VR” and judged the organisation to be “operating at half the effectiveness that would make me happy.”