DOOM (Source)

A Doom source port is a source port of id Tech 1, the game engine used by the video game Doom. The term usually denotes a modification made by Doom fans, as opposed to any of the official Doom versions produced by id Software or affiliated companies.

Doom source release
The source code for the Doom engine was released to the public in 1997. Although Doom was originally created for MS-DOS, the original source release was for the subsequent Linux version. This was primarily due to use of a proprietary sound library in the DOS version. Since the source code had to be initially ported back to DOS, the term "source port" was used. Out of custom, this term has come to be used for all Doom source modifications, even those that are not technically ports to another platform.

The original purpose of source ports was cross-platform compatibility, but shortly after the release of the Doom source, programmers were correcting old, unaddressed Doom bugs and deficiencies in their own source ports, and later on added more source code to enhance game features and alter gameplay.

Doom source ports have been created to allow Doom to run on many different operating systems and computer architectures, including Linux, Mac OS X, and Windows, even GP32 and GP2X, two Korean handheld game systems capable of running homebrew games. Also, a British company called WildPalm has produced a port to the Nokia 7650 and 9210 cell phones. There is a port to the Sega Dreamcast, as well as the Xbox video game system. Also, Doom is run on the iPod through alternatives such as Rockbox and iPod Linux.

The source code was originally released under a proprietary license that prohibited commercial use and did not require programmers to provide the source code for the modifications they released in executable form. As a consequence of the source code for GLDoom, the first port to add OpenGL graphics to Doom, being lost in a hard disk crash, the code was re-released in 1999 under the GNU General Public License after requests from the community.

Major source ports
These are source ports that have garnered a large following in terms of number of users or number of available modifications, or those that possess unique and interesting features, some of which have been considered technically impossible within the confines of the Doom engine at varying times.

Boom and derivations
Boom was a port of the Doom source code by TeamTNT. Boom fixed numerous software glitches and added numerous other software enhancements into the engine to such a degree that its additions have been incorporated into most modern day Doom engines (such as ZDoom and Doom Legacy).

Although Boom is simpler than the other ports and is no longer updated, it is often preferred, as it has stayed relatively close to the behavior of the original games, including demo support. However, some of the bug fixes and behavior changes of other ports may unbalance how maps made for the original games play, giving players certain advantages or disadvantages.

Eternity Engine
The Eternity Engine is a Windows source port licensed under the GNU General Public License. It was originally meant to power a Doom total conversion, but after that project went on hiatus (eventually being canceled) the engine became the prime focus. The engine is based on Smack My Marine Up (SMMU). It includes such features as scripting, portals, polyobjects, and Heretic support.

Marine's Best Friend
Marine's Best Friend (MBF) is a DOS-based source port. It is based on Boom, and adds several new features including high resolution graphics, enhanced monster AI, emulation of the pre-release beta versions of Doom, and "helpers" that follow and help the player (specifically dogs, to which the name of the engine refers). It was developed by Lee Killough in 1998 and is now discontinued. Its code was later used as the base of the source port Smack My Marine Up, which in turn was used to construct the Eternity Engine. In 2004 James Haley and Steven McGranahan ported Marine's Best Friend to Windows as WinMBF.

PrBoom
PrBoom is a Doom source port derived from Linux and Windows ports of Boom and MBF that includes an optional OpenGL renderer as well as options allowing it to restore the behavior of earlier executables (such as Doom 1.9, Boom, and MBF) in essential ways. Initially designed for use in Windows and Linux, it has also been ported to Dreamcast, GP2X, Nintendo DS, Wii, and Rockbox. A variation named PrBoom+ provides enhanced demo recording and viewing capabilities. id Software's official Doom iPhone port is based on PrBoom. The source port is packaged in the Ubuntu Software Center as well as Fedora's RPM software repository alongside Freedoom.

Chocolate Doom
Chocolate Doom is a source port that aims to reproduce the behavior of the original Doom engine as closely as possible (a purist approach). This includes being compatible with nearly every Doom, Doom II and Final Doom WAD, demo and savegame that works with the original executables. The port runs on many operating systems, including Linux, Mac OS X, Microsoft Windows and OpenBSD.

The port's name is wordplay with the term vanilla Doom sometimes used by Doom fans (especially those regularly using modified source ports) to refer to unmodified Doom engine behavior or to the out-of-the-box executables.

Doomsday Engine and derivations
The Doomsday Engine is a GPLv2-licensed source port that runs on Linux, Mac OS X and Windows. The port also supports Heretic and Hexen. Its hardware-accelerated engine supports 3D models, object and movement smoothing, shadows, dynamic lighting, and other features. It also includes XG line and sector types for editing extensions, as well as a built-in master server games browser (launcher).

Risen3D
Risen3D is a Windows only fork of the Doomsday Engine (based on v1.7.8 released on March 15, 2003). It was originally known as Boomsday as it only added support Boom map editing features.

DOSDoom and derivations
DOSDoom was one of the first Doom source ports, created by taking the original Linux release of the Doom source code and porting it back to DOS. It evolved to include several new features, which were previously unseen at the time shortly after the release of the original Doom source code, such as translucency, high resolution, and 16-bit color rendering.

Doom Legacy
Doom Legacy is a source port originally written as a fork of DOSDoom, introducing mouse-look, jumping, a console, 32-player deathmatch, skins, and, later, native Windows, Linux and Mac OS X ports. It has also evolved to support many Boom features and 3D acceleration. It also adds a few new features, notably the ability for levels to contain floors directly over floors, which means levels are not required to be strictly 2D as in the original Doom.

EDGE
Enhanced Doom Gaming Engine, or EDGE, is a port derived from DOSDoom. The most attractive feature of EDGE is its DDF system, which describes all game behavior inside text files external to the executable file. As a result, it is popular among Modifiers. who use the extensibility to add many new weapons and features with many fewer of the limits present in other source ports. EDGE includes ports to many operating systems, including MS-DOS, Windows, Linux, BeOS,Mac OS X.

ReMooD
ReMooD is a source port based on Doom Legacy. It can be compiled and run on 64-bit systems natively.

Vavoom
Vavoom is a source port created by merging the Doom, Heretic, and Hexen source trees to create a unified executable. It also features bits of the Quake source (used predominantly for networking and rendering), and was the first port to support Strife. It has been in development since September 1999, and was first released in June 2000. Among its features are a true 3D polygonal engine with colored lighting and software, Direct3D and OpenGL renderers, freelook support, 3D floors, and support for Boom's extended attributes. The source port is packaged in the Fedora RPM software repository alongside free installers that grab the shareware levels for all the games used by the engine by default.

ZDoom and derivations
ZDoom is a source port targeted at Microsoft Windows and Linux. It is one of the most advanced and featureful Doom ports from an editing perspective, supporting Boom editing extensions, plus all the extensions made by the Hexen engine, as well as many other new features. In addition, it supports Chex Quest, Heretic, Hexen, and Strife. The breadth of its features has allowed the development of some indie games, including Foreverhood, Urban Brawl, and Harmony.

csDoom
csDoom, or "Client/Server Doom", was a GPL source port based on ZDoom built expressly for playing multiplayer games of Doom over the Internet. It was the first port to use client/server network code (from Quakeworld) to help facilitate smoother Internet games. The project was closed by the creator in early 2001.

GZDoom
GZDoom is a source port based on ZDoom that extends its feature set to include an OpenGL renderer. It also boasts 3D floor support compatible with Doom Legacy and Vavoom, 360 degree skyboxes, 3D model support, and other features.

Odamex
Odamex is another multiplayer-centric source port based on csDoom. Odamex includes the features of the Boom engine, and currently supports Capture the Flag mode and support for up to 255 players. The goal of Odamex is to expand the base of possible players to multiple computing platforms, including Windows, Linux, Mac OS, and other operating systems. Odamex is free software, and is currently in development.

Skulltag
Skulltag is one of the multiplayer-centric Doom ports that is based on (G)ZDoom. In addition to client/server networking code, Skulltag includes bots for offline multiplayer games; new game modes such as Capture the Flag, Skulltag, Invasion, Duel, Survival, Teamgame, and others; as well as new weapons, monsters, items, powerups, artifacts and gameplay-modifiers such as Instagib (a spinoff of Deathmatch where all players spawn with a railgun that gibs other players in just 1 shot). Skulltag supports Heretic, Hexen and partially Strife, and the package also includes a server browser, the Internet Doom Explorer Skulltag Edition (IDESE), for joining online games in progress. Skulltag also features enhanced graphics, such as OpenGL rendering (based on GZDoom's renderer), high quality resizing, and support for HD screen resolutions. It also has support for models and high-resolution textures. Skulltag also features its own resources for map editing and such.

ZDaemon
ZDaemon is a source port, originally based on ZDoom, for both Windows and UNIX (server only), purposely-built for playing multiplayer games of Doom over the Internet. While it was formerly open source under the GPL, the source has been closed due to cheating incidents and security issues. The game includes client/server network code for Internet play, a launcher to help users easily find games to join, a favorites list so they can re-visit their favorite servers, a utility for automatically finding and downloading custom WAD files needed to play on particular servers, and support for Heretic and Hexen.