There have been many Free Software first-person shooters (FPS) projects over the years, from modded Doom and Quake engines to enhance the existing games (ezQuake, EGL, ZDoom), to free art packs such as OpenQuartz or OpenArena. In 2002, along came Cube, a single and multiplayer FPS based on its own engine, including artwork, maps, models and an ingame map editor. In the freeware (and Linux compatible!) world, a little-known Tribes-inspired game called Legends appeared, yet remained closed source. Filling the FPS gap in the Open Source world has usually been left to commercial companies who release their games with Linux support (i.e., Doom3, Unreal Tournament 2004, Loki Software's work), or to freeware games produced by commercial studios (i.e., America's Army, Wolfenstein: Enemy Territory), or to simply running Windows games run via Wine.
In the last few years, a few built-from-scratch community-based FPS projects, most built on the GPLed Quake engines, have popped up. Among them are Tremulous, Alien Arena, Nexuiz, and Warsow. Some have kept their art assets under a closed license (Warsow), while others have also released their art under an OSS license (Nexuiz). I consider both categories Free Software, since "software" refers to programs, code and procedures, not artwork. For this comparison, we'll take a look at active, robust and community-developed Free Software shooters. Most released Free Software shooters are designed for multiplayer use (a logical step for a game developed in an online community fashion), yet most also feature a bot-based single player mode. While others have compared such games before, this feature seeks to be a little more thorough and go a step further, ranking the following seven games: Alien Arena, Nexuiz, OpenArena, Sauerbraten, Tremulous, Warsow, and World of Padman. In ranking these games, gameplay, design, innovation, and presentation (in that order) will be held as primary criteria.
Sauerbraten is basically Cube 2, the sequel to one of the most influential Free Software shooters released to date. The engine is completely reworked with brand new graphics-rendering features (rivaling those of Quake4) and additions to the map editor features. Like Cube, Sauerbraten has a built-in map editor that allows the player to edit maps from within the game. The game is still in heavy development. Sauerbraten gameplay doesn't really differ from anything Cube offered, with simple Quake-style weapons, game effects, and the same Quake3-like FFA action.
It is worth noting that Cube (and Sauerbraten) give you a weapon when you pick up the appropriate ammobox; there is no separation between ammo and weapons. While it has some cool features, the game still feels like more of a concept demo than an actual game, and with only 20-30 servers (half running instagib), there isn't much of a community following. The single player mode is reminiscent of Quake1, with enemy monsters in a variety of maps. The menu is actually one of the coolest I've seen implemented in a game. It spawns as an object ingame and faces you, though the lack of a main menu upon loading adds to the tech-demo feel. Despite the tech-demo nature of the game, Sauerbraten has a good soundtrack, lots of maps, good quality models, and well-done artwork and textures. The gameplay isn't anything astounding, but with pretty decent maps and gameplay reminiscent of Quake3, Sauerbraten definitely offers something for people who just want some simple, mindless action with some eye candy. Sauerbraten is a really cool project, but right now it remains that, a project showing what can be done, more than a game.
OpenArena is a project to create GPL-licensed art assets on top of the Open Sourced Quake 3 engine. It uses the latest svn snapshot of the ioquake3 engine and a mix of GPL assets ranging from original work to resources from Nexuiz, Cube, and others. It is a fairly large release at over 200MB. Most of the space is spent on many maps and models, some of which are regrettably lacking in quality. Some are straight recompiles of the GPL-released Quake 1 maps (oa_dm1-7), which fail to use many of the advanced lighting and details offered in the new engine. OpenArena seems to generally lack coherent art direction or design. Most the maps, models, and artwork seems like a half-done mix of Quake 3's Gothic architecture and Anime.
The gameplay stays true to what was included in Quake3, so it can be rather enjoyable. On the other hand, Quake 3 Arena was a great game because it was done in such a simple, directed, and polished manner. OpenArena lacks much of the polish that made Quake3 so enjoyable. The goal of recreating GPL Q3A artwork on top of the GPL code is a very noble and useful goal, yet the project is still in its early stages, and the task at hand is a rather large one. Games still seem limited to FFA games, and with about 70 servers, the community is rather small. While Q3A gained popularity as a competitive game, the developers of OA don't see that as a target market, so the depth of gameplay is unlikely to expand. Tremulous, Warsow, even Nexuiz all display far better art direction and design. At the end of the day, though, OpenArena is about making a Free game that has lots of simple and fun deathmatch action à la Quake3, and that is where it succeeds.
Alien Arena is a Quake 2-based game with humans and aliens, yet there isn't much of a difference outside player models. It still has many visual characteristics that are reminiscent of Quake 2. With a dark artistic style and fast gameplay with strong weapons, Alien Arena is still predominantly a deathmatch game. There are modes like deathball, CTF, assault, and a unique gametype called "cattle prod". Some maps also feature vehicles, but they aren't very well presented and seem to be underutilized. Although the external server browser and main menu are very nice, much of Alien Arena seems to be muddled and lacking polished design. The HUD lacks many critical features like a weaponlist or a clock, and the icons and graphics don't seem very sharp or clear. Alien Arena lacks many obvious features like removing the quad powerup for the duel gamemode. While many of the weapons seem to be recreations of weapons in Unreal and Quake, the two fire modes for each weapon adds interesting diversity on top of Quake-inspired gameplay rules. The overpowered nature of the weapons (especially the chaingun) leaves much to be desired.
The community isn't very large at about 60 servers, but since the game seems to be a bit lacking in clean presentation, it might not be too attractive to new players. It seems to be working with lots of new and interesting original concepts, but still needs work to match the artistic and gameplay quality of the other games covered here. If the project were to shift gears and focus a bit more on polish, design, and presentation instead of creating tons of content (which it already has), it has the potential to move beyond "dark FFA deathmatch action" and really be something quite original and remarkable.
Nexuiz is another game that follows the fast, dark, and intense free-for-all deathmatch style first set down by Quake 1 in 1996. Nexuiz, curiously enough, is built on the Darkplaces engine, an expanded version of the GPL-released Quake 1 source. While the basic graphics seem to be up to Quake 3 standards, expanded lighting options allow the graphical features to be brought up to just below Quake4 standards. Although the newest version still follows that simple deathmatch style, the fast, varied maps and lots of explosive action with interesting two-fire-mode weapons lead to gameplay that is about as intense as it gets for shooters. Good sound combined with varied and unique weapons attests to the polish that has gone into bringing Nexuiz up to version 2.3.
Nexuiz has lots of maps which seem to be slightly varied in style but still with dark overtones. While most of the game is cleaned up far beyond its Quake 1 roots, it is still lacking in presentation, with the menu being very circa 1990s. The community is strong, and with about 80 servers, there are most definitely games to be found. Nexuiz has lots of content, style, and features, and is very well done for an FFA game, but some areas could use some more work and showcasing of its features and modes.
World of Padman originated as a modification of Quake 3 in 2004. With the release of GPL-licensed Quake3 code, World of Padman was released as a stand-alone game on top of ioquake3. From that perspective, World of Padman was designed more in the style of the mod community (art-driven projects) than that of the Free Software community (code-driven projects). Nonetheless, it's Free Software now.
The game is based on a comic book and has unique colorful graphics with clear comic inspiration. Gameplay is very similar to that of Quake3, a little bit different, a little refreshing, but nothing too strikingly new. Killing other players is satisfying and just silly fun. If anything, World of Padman is proof that deathmatch gaming doesn't need to be blood-covered, violent, and serious. It can be silly, cutesy, and fun. World of Padman features several maps, each unique yet still based on being a small character fighting in a real-world room. It's not a new approach for maps, but it definitely is fun and interesting. Combined with World of Padman's art direction, this leads to rather refreshing arenas.
Players are characters about 3cm high and fight in real rooms like a bedroom, library, kitchen, etc. The maps are covered with jump pads and fun little powerups. While maps like this are great free-for-all fun, they aren't really designed for competitive play, limiting potential for a hardcore community. Gameplay is similar to Quake3, but a bit different, with slower rockets and a very satisfying machine gun perhaps the most notable changes.
World of Padman has a small community at about 26 servers, but lack of gameplay innovation is what hurts this game the most. The game is very polished and has several gamemodes (including a unique "Spray your Color" mode), and gameplay still boils down to basic Quake-like fragging. While World of Padman is by no stretch of the imagination a bad game, it lacks the innovative gameplay design goals of several of the games features here. While the game has great style rivaling the stylistic nature of any commercial game, it lacks advanced graphical features like Nexuiz and Sauerbraten or unique gameplay features like Nexuiz and Alien Arena. If you want to see what the Gothic Quake 3 would look like if it were designed by color-loving comic artists with a sense of humor and a sense of fun style, World of Padman is exactly what you're looking for. Regrettably, that's about as far is it goes at the moment.
Tremulous sets itself aside from all of the previous games in that it isn't an FFA deathmatch game. Instead, Tremulous is a team-based game with aliens vs. humans in which each team constructs a base and can use its kills to level up its players. With a kill-based point system, Tremulous rewards combat, since it allows players to get better equipment so they can better attack the opponents. The two teams are unique, and the concept and style of the game is rather original. If anything, Tremulous can be related to the Half-Life mod Natural Selection, although without the RTS mode.
Tremulous has had a very constant release cycle, with the latest 1.1 being released about a year ago, yet the community and development still remain active. The game is based on the Quake 3 engine, and although there are only eight maps, they have sufficient variety and uniqueness that it feels enough. The two first things that I noticed about the game were that the options menu didn't show up until the player joined a game and that the game was really complex, but guided the player well, featuring onscreen help and tips while you play. The game comes with a descriptive and friendly manual for those who want to learn the gameplay quickly.
The game is simply fun. There is just plain action for those who want a simple game and tons of features and detail for those that want a bit more. The graphic design is consistent, dark and sci-fi futuristic with a bit of variance but a lot of consistency. The game has a large following (as Free Software goes) with a about 200 servers and at least a couple games any time of day. The performance is clean and consistent, and it looks as good as Quake 3 generation mods.
Tremulous is one of the few Free Software projects to combine an original idea with a polished implementation and good direction. The few maps and one gamemode really keep the community and style focused and clean. Tremulous could use more maps, more variety, more content, and perhaps more robust gameplay, but 1.1 is a great release, and future versions are definitely something to watch out for.
Warsow is a deathmatch shooter with a focus on freedom of movement, attracting new players and fostering a competitive scene. It is based on Qfusion, a heavy modification of the GPL Quake 2 engine. From the user interface to the game and netcode, the game feels more like an improvement on Quake 3 than anything, stretching far beyond the original engine.
Along with World of Padman, wSw stands out in this comparison by using colorful and clean graphics as opposed to Quake-inspired dark visuals. Warsow manages set itself even further by using cel-shading to create very clean, yet stunning visuals. While sticking to basic gamemodes, wSw manages to refine them to be simply fun and enjoyable. Weapons are generally the same as Quake 3 and 4, with a more fun and refined feel. wSw implements a dual tier system for ammos, with weak and strong ammos which add more functionality to the gameplay while still keeping the basics simple.
Warsow's main change to the basic Quake 3-style gameplay is an expansion of movement options, featuring strafejumping and bunnyhopping from Quake along with dash, walljumping, and aircontrol. Polish and high quality standards are what make Warsow the Free Software FPS to beat. All aspects, from movement to maps to the gamemodes, seem refined and balanced. It was not until the mid-2007 release of the 0.3x version (currently 0.4) that wSw became refined enough to set itself apart from the others mentioned here. While many of the previously-mentioned games have good original ideas and interesting features, they do not present games that match the quality of commercial offerings. In terms of multiplayer features and customizability, Warsow matches and outclasses any released commercial deathmatch game. While the other games seem to fall into the common trend in Free Software projects (lots of great ideas without friendly and useful implementation), Warsow is in the style of Firefox or OpenOffice, polished and accessible. In addition, the maps all feature a unique visual style that varies between maps yet retains the clean and cyberpunk visual themes of wSw. The voice-overs are clean and unobtrusive, unlike those of some of the previously-mentioned games. Warsow has good art design coupled with refined gameplay and tons of maps (which have good flow and consideration of gameplay and item placement).
Of the games reviewed here, Warsow has the largest community, with over 250 servers. Competitive gaming is key to wSw, and there exists a very large competitive community, so much so that wSw was used for an international LAN competition in 2007. Competitive gameplay drives many of the design decisions behind the game, always leaving players with something to do and strive for. Yet this also leads to the game's largest flaw, a steep learning curve that drives wSw beyond the scope of many casual gamers. Many players are very good, and new players are often crushed when they play against them, although the CA mode lets new players have a simple gamemode in which they can stand a bit more of a chance. Also, wSw thrives on bunnyhopping and strafing skills which take time to develop. Tutorial videos exist, but lack of an ingame tutorial seriously limits adoption. Duel and TDM have large active competitive communities, and there is a large public iCTF and CA scene as well.
Warsow is loaded with lots of graphical features (bloom, stencil shadows) which are scalable but can run slowly on older systems. Warsow also features adaptive lag compensation in order to allow for smoother online play. High-quality art direction, the implementation of simple, yet effective original ideas, and the refining of Quake gameplay leave Warsow the champion of the pack for Free Software shooters. Warsow was able to do what many Free Software projects strive for, take a simple, established concept, implement some very clear, simple, and original ideas, refine the core of the project, then present it in a very professional way.
Currently in heavy development, Quake2world is based on the Quetoo source cleanup of the Quake2 engine. It is full of features, and the gameplay is fast and unique, combining the speed of QuakeWorld with features and level design of Quake2, with the possible induction of more features from other Quakes. There is high quality artwork being developed, but development is still very much a moving target, with no actual releases, though there is a publicly-accessible SVN and a handful of servers.
Legends offers Tribes-inspired gameplay with years of effort behind it. While Legends isn't Open Source, it is worth a look if large environments in team-based combat is your thing.