Duke Nukem 3D | Code Like It's 198x

In Duke Nukem 3D the toilets work. Walk up to one and Duke uses it, with sound effects; kick it and it sprays water. There are pool tables to play with, security cameras to look through, and a strip club full of aliens. Nothing in Doom worked like this. 3D Realms’ shooter of 1996 filled its levels with things that did something when pressed, shot or kicked, set them in streets, shops and clubs instead of abstract bases, and gave its hero a voice: a stream of one-liners from a muscle-bound action-film parody. Underneath was Ken Silverman’s Build engine, which let walls, floors and doors move in ways Doom’s could not.

Fast facts

Developer: 3D Realms, the 3D games label of Apogee Software.
Engine: Build, written by Ken Silverman.
Released: January 1996 as shareware; the full game followed in April 1996, published by FormGen in America and US Gold in Britain.
Multiplayer: up to eight players on a local network, or two by modem.
Voice of Duke: Jon St. John.
Source code: the Build engine’s in 2000, the game’s under the GPL in 2003.

From platform hero to shooter

Duke began as the hero of Apogee’s side-scrolling Duke Nukem (1991). “Duke came from nothing special,” George Broussard, the 3D game’s executive producer, told Retro Gamer. “The name rhymed and nuking things sounded cool. That’s as deep as character design got in those days.” What changed in Duke Nukem 3D was personality. “You weren’t just a faceless marine,” Broussard said. Much of what people remember, he added, came late: “a lot of things, like Duke talking, the interactivity, the strippers and pop culture references, were added in the last four to five months of development.” The team had John Wayne and Clint Eastwood in mind. Duke’s lines, delivered by the radio presenter Jon St. John, borrowed from action films. In a 1996 list of computer game heroes, Computer Gaming World ranked him seventh: “Although Duke’s been around, he never had quite so much personality as he showed with the delightful voiceovers for his latest incarnation.”

The Build engine

Build was written, Edge reported in 1995, “single-handedly by teenage programming genius Ken Silverman”. Computer Gaming World described him as a self-taught programmer from Rhode Island who had first approached Apogee with his own game, Ken’s Labyrinth, and who wrote the engine in C with assembly-language routines for the slowest work, drawing textured lines of wall and floor. “He’s just brilliant—he’s a programmer from Venus,” Apogee’s Scott Miller said.

The engine describes a level as sectors: closed polygons on the map, each with its own floor and ceiling height, which can slope. Sectors join through shared walls that work as windows into the next sector. Doom worked out what could be seen from every point in a level in advance, when the map was built, and stored the answer as a binary space partition tree, so its walls could never move. Build works out what is visible as it draws each frame, by following those shared walls outwards from the sector the player is standing in. That costs more processor time, but it means the map can change during play. Computer Gaming World’s Paul Schuytema found that a sector was “more like a ‘region of interest’ than a room”: a pool of light, a cash machine or a desk could each be one. Apogee insisted on 20 frames a second on a 486 running at 66MHz, though level designer Allen Blum said they wished everyone had a Pentium.

Broussard listed what that bought: “you can walk over bridges, have true rooms above rooms, swim underwater, have mirrors on the walls … look up and down, duck, crawl, jump, fly.” Some of it was sleight of hand. Rooms above rooms were made by quietly moving the player between separate parts of the map, and a mirror was a room drawn a second time from a reflected viewpoint into a space left empty behind it.

A world to play with

In the moon-base level Edge saw before release, a rocket fired across a room blew out a window, and the change in pressure sucked out the aliens, and Duke too if the player did not shut the door in time. Bullets left pock marks on walls; earthquakes shifted whole sections of a level to open new routes. Computer Gaming World listed the toilets, which could be used or kicked to release “lovely blue geysers”, and the dancers in the strip club, who could be tipped. Retro Gamer added clocks, microphones and pool tables. “Do they remember shooting the 100th Pig Cop or the pool table?” Broussard asked. “I think that stuff added a lot and was one of the core reasons [it] was a success.”

The weapons were built in the same spirit. After the pistol, shotgun, machine gun and rocket launcher, “we just started to play with new ideas for guns that were just fun,” Broussard said, such as the shrink ray, which lets Duke step on his enemies, and the freeze gun. Bombs could be scattered up to 50 at a time and set off together, Edge noted, and laser-triggered mines left in corridors. A holographic decoy, the Holoduke, drew enemy fire, and a jetpack lifted Duke over the city.

Reviews and controversy

Edge reviewed the shareware episode in April 1996 and gave it eight out of ten. It admired the engine, which ran “faster than every other comparable 3D PC title” even at 800×600, and levels “packed with huge ramps, drops, lifts, jumps and cunningly hidden secret areas”. It found the enemies silly rather than frightening, and the game “just not scary enough”; its caption called it “the second best game of its kind on the PC, after Doom”.

The strip club, the adult bookshop and the jokes were deliberate. Computer Gaming World’s preview summed up the content as “politically incorrect gratuitous violence and sex”. Broussard defended it to Retro Gamer years later: “We knew we’d get some heat for it, but we didn’t care. We were all adult game players and were tired of cute cartoony games.” The strippers and the adult bookstore, he said, “were less than one percent of the game”, though the team placed them very early on purpose.

It sold, too: in December 1996, eleven months after the shareware release, it was still among the best-selling PC games in America, according to the PC Data chart Computer Gaming World printed.

Add-ons and other machines

Duke Nukem 3D was built to be added to. Silverman’s level editor came on the commercial CD, and 3D Realms followed with its own fourth episode, the Plutonium Pak, published by GT Interactive and reviewed by GamePro in February 1997. It added new levels set in a supermarket, an amusement park and a police station, and a new weapon, the Expander, which inflated enemies until they burst. Further add-on packs included Duke It Out in D.C. (1997), ten levels set around the Washington Monument, the Capitol and the Smithsonian, and Duke Caribbean: Life’s a Beach.

Three console versions arrived in 1997. Lobotomy Software’s Saturn conversion was Sega Saturn Magazine’s highest-rated Saturn game of the year, at 97 per cent. The PlayStation got Duke Nukem: Total Meltdown, and the Nintendo 64 Duke Nukem 64, which kept the toilet and the pool table.

Released source code

Silverman published the Build engine’s source code on 20 June 2000, after finishing college, under a short licence of his own that asks those who use it to credit him. 3D Realms released the source code of Duke Nukem 3D itself on 1 April 2003, under the GNU General Public License. With both halves public, fans ported the game to modern systems; by 2007 Retro Gamer was recommending a port called JFDuke3D and a fan-made pack that replaced the sprites with 3D models.

The engine outlived its maker’s game. 3D Realms, under new owners, published Ion Fury in 2019, a new shooter built on Build. A sequel, Duke Nukem Forever, was in development from 1997 and did not appear until 2011; the 3D Realms entry tells that story.

Sources

Edge issue 24, September 1995, pp. 29–32: 3D Realms studio feature (Build “single-handedly” by Ken Silverman; Broussard’s list of Build’s advantages; the moon-base depressurisation).
Edge issue 31, April 1996, pp. 78–79: review of the shareware version, eight out of ten (publisher US Gold; 800×600; pock-marked walls and earthquakes; the Holoduke, the wall-mounted cameras, 50 bombs and laser-triggered mines).
Ken Brown, Duke Nukem 3D preview, Computer Gaming World issue 141, April 1996, p. 51: shareware download; eight players on a network or two by modem; the toilets and the strip club; the Holoduke and the jetpack; “politically incorrect”; Apogee/FormGen.
Paul Schuytema, “The Build Engine”, Computer Gaming World issue 142, May 1996, pp. 107–110: Silverman, Ken’s Labyrinth, C and assembly language; sectors; Build against Doom’s BSP; 20 frames a second on a 486-66 and Allen Blum’s comment; Miller’s quotation; the editor on the CD.
Computer Gaming World issue 148, November 1996, p. 124: Duke Nukem seventh in its list of game heroes (Duke Nukem 3D, FormGen/3D Realms, 1996), for his voiceovers.
Computer Gaming World issue 153, April 1997, p. 36: PC Data’s list of top-selling PC games for December 1996, including Duke Nukem 3D (FormGen).
Computer Gaming World issue 190, May 2000, p. 49: quiz question naming “the voice of Duke Nukem — radio DJ” Jon St. John.
Major Mike, Plutonium Pak review, GamePro issue 101, February 1997, p. 55: new levels (supermarket, amusement park, police precinct), the Expander, GT Interactive.
Computer Gaming World issue 154, May 1997, p. 33: Duke It Out in D.C., ten levels and its landmarks.
Giochi per il mio computer (Italy) issue 35, February 2000, p. 107: the expansions Caribbean: Life’s a Beach and Duke It Out in D.C.
Sega Saturn Magazine issue 28, February 1998, p. 11: Lobotomy’s conversion, 97 per cent, highest-rated Saturn game of 1997.
GamePro issue 111, December 1997, p. 88: Duke Nukem: Total Meltdown review (PlayStation).
Nintendo Magazine issue 62, November 1997, p. 34: Duke Nukem 64, the toilet and the pool table.
“The Making of Duke Nukem 3D”, Retro Gamer issue 39, 2007, pp. 67–69: Broussard’s quotations; the interactive objects; the weapons; John Wayne and Clint Eastwood; JFDuke3D and the High Resolution Pack.
Ken Silverman, “Build Engine & Tools” source release page (web): source released 20 June 2000, with its licence (BUILDLIC.TXT); “04/01/2003: Duke Nukem 3D source code released by 3D Realms”. https://advsys.net/ken/buildsrc/
Fabien Sanglard, “Duke Nukem 3D Code Review” (web, secondary): engine source released by Silverman on 20 June 2000, game source by 3D Realms on 1 April 2003; sectors joined by portal walls; visibility worked out at run time; mirrors; “true 3D” via teleporters. https://fabiensanglard.net/duke3d/ and https://fabiensanglard.net/duke3d/build_engine_internals.php
“Code source de Duke Nukem 3D en GPL”, LinuxFr.org, 2 April 2003 (web, secondary): 3D Realms makes the source code available under the GPL. https://linuxfr.org/news/code-source-de-duke-nukem-3d-en-gpl
“Duke Nukem 3D”, Wikipedia (accessed October 2026) (web, secondary): shareware release on 29 January 1996 and full release on 19 April 1996; the source code under the GPL on 1 April 2003; Jon St. John. https://en.wikipedia.org/wiki/Duke_Nukem_3D
For Ion Fury, Duke Nukem Forever and 3D Realms’ later history, see the 3D Realms entry and its sources.