Freedoom is an entirely free software game based on the Doom engine.
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Freedoom

The Freedoom project aims to create a complete, free content first person shooter game, but Freedoom by itself is just the raw material for a game. It must be paired with a compatible Doom engine to be played.

There is a massive back catalog, spanning over two decades, containing thousands of Doom levels and other modifications (“mods”) made by fans of the game. Freedoom aims to be compatible with these and allows most to be played without the need to use non-free software.

Freedoom is actually three games in one, consisting of two single-player oriented campaigns and one set of levels designed exclusively for multiplayer deathmatch:

Freedoom: Phase 1

Four chapters, nine levels each, totalling 36 levels. This game aims for compatibility with The Ultimate Doom mods, also known as plain Doom or Doom 1.

Freedoom: Phase 2

32 levels in one long chapter, featuring extra monsters and a double-barrelled shotgun. This project aims for compatibility with Doom II mods.

FreeDM

A 32-level game designed for competitive deathmatch play.

The engine uses a single file, such as freedoom2.wad, that contains all the game data such as graphics, sound effects, music, and so on. This file is often called an “IWAD” by those in the Doom and Freedoom communities. While the Doom engine source code is free, you would normally still need one of the proprietary data files from id Software to play Doom. Freedoom aims to create a free alternative: combined with the GPL-licensed Doom source code, this results in a completely free game.

For more information, see http://freedoom.github.io/.

How to play

Since Freedoom is only the game data, you will still need to download an engine separately. These are also often termed “source ports” by the community. There are an overwhelming number of choices available, a lengthy list of which is available on the Doom Wiki.

One particularly recommended by the Freedoom project is GZDoom. This engine offers good support for single-player, multi-player, and the majority of mods created for both Doom and Freedoom.

On Windows, you should place Freedoom's data files (those ending with .wad) alongside the engine (eg, odamex.exe). On Unix-like systems, these data files should go in either /usr/share/games/doom or your home directory. If Freedoom comes packaged as part of your operating system distribution, it should already be installed into the proper location.

If you wish to venture outside of GZDoom, beware that Phase 1 and Phase 2 require a limit removing engine, which is thankfully the majority of them, but not all. FreeDM, on the other hand, is intended to be playable by all variants of the Doom engine.

Hopefully, your engine of choice should already be capable of running Freedoom without extra configuration. This may not be the case, however, if the engine does not recognize any of the filenames for Freedoom, and might require manual intervention to make it so. One of the following options should solve it:

  • Use the -iwad command line parameter. For example, to play Phase 2, you can enter -iwad freedoom2.wad either at a command line, or adding it to an application shortcut.

  • Use the DOOMWADPATH environment variable. Many engines support this variable to add directories and/or files to their search path. The exact syntax matches your operating system’s normal PATH environment variable.

  • Rename the game files. This may be a bit crude, but you can rename the files to match those of Doom's. This is often the easiest quick-fix, although it is normally desirable to use one of the above methods if possible.

    • freedoom1.wad can be renamed to doom.wad

    • freedoom2.wad can be renamed to doom2.wad, tnt.wad, or plutonia.wad

    • freedm.wad can be renamed to doom2.wad, tnt.wad, or plutonia.wad

Additionally, for Unix-like operating systems, such as GNU/Linux or a BSD variant, Freedoom may be packaged and installed with programs named freedoom1, freedoom2, and freedm that automatically run an engine for proper play. Desktop files may also be installed so that you can start the game using a graphical interface and avoid the command line altogether.

What “free” means

When we speak of free content or software, we refer to the movement in which your freedoms to use, copy, modify, and study a work is not infringed. For example, you may freely use Freedoom for any purpose you see fit, you may redistribute it to anyone without needing to ask for permission, you may modify it (provided you keep the license intact, see COPYING), and you may study it—​for example, to see how an “IWAD” is built. To facilitate this, you can get the full source code for Freedoom, in this case, in the form of a DeuTex tree.

You may read more about free software at the GNU and Free Software Foundation websites.

Contributing to Freedoom

Contributions to Freedoom are always welcome, however there are a few guidelines that should be followed:

Intellectual property

We know people hate legalese, but this is important. This applies to everything which is submitted.

You must be incredibly careful when basing on existing graphics or sounds. Most Doom projects are incredibly lax on reusing intellectual property—​there are many mods which contain modified Doom sprites, for example. However, due to the nature of this project, we do not have the same liberty to rip as we please.

The general rules go as follows:

  • You must have permission for everything you submit. If you make your own resources, do not base on resources from Doom or any other restricted work. If you take work from other places, please make sure that the work is freely-licensed or that you obtain permission to include it in the Freedoom project. They may not place additional restrictions compared to the normal Freedoom license.

  • Do not try to emulate Doom resources exactly. Where possible, put effort to make new versions look visibly different from Doom. This is a tough call, because our compatibility with Doom mods limits how far we can deviate, but it is feasible.

  • Be especially careful of “free textures” (or “free sounds” or “free graphics”) sites. Although these would appear at first to be okay to use, many are free for “non-commercial use only.” One of the things we want to be able to do is put this in GNU/Linux distributions (which can be sold or developed commercially).

Levels

Levels for Phase 1 and Phase 2 must be compatible with any limit removing engine. This means that you may exceed the limits of the original Doom, but do not depend on any additional mapping features. Levels should be in Doom's original format, not in “Hexen”-format.

It is a goal that future versions of Freedoom will be entirely vanilla-compatible, not even allowing expanded limits. Keeping this in mind while mapping may make it easier for your level to be preserved. Levels requiring large amounts of modification to fit into vanilla limits may be discarded entirely in favor of a less complex map.

Levels for FreeDM must strictly be vanilla-compatible, that is, they must run in the original doom2.exe engine for DOS and not cause any visplane overflows and other such problems in the vanilla engine. This ensures the maximum compatibility with all Doom-derived engines.

It is sensible to also heed the following guidelines:

  • Make sure that skill levels are implemented, and that all multiplayer start points, both cooperative and deathmatch, are present.

  • Try to make levels appropriately difficult for their position within the progression of the game. Also bear in mind that not all players may be as skilled a player as you.

  • Do not use tricks that exploit Doom's software renderer; some engines, especially those that use hardware accelerated rendering, may not render it properly. Examples of tricks to avoid include those used to simulate 3D bridges and “deep water” effects.

  • While unrestricted by limits, do not make excessively complicated scenes. It is desirable that Freedoom levels should be playable on low-powered hardware, such as phones and old computers.

  • For Phase 1 and Phase 2, try to test your levels in Crispy Doom, which is an engine that is limit removing but does not introduce mapping features to accidentally exploit.

  • For FreeDM, while you can test in the original doom2.exe engine with DOS or an emulator, this original engine is not free software and not legally obtainable without Doom, in addition to the hassle of merely running it. Chocolate Doom is a free software, highly-portable, and strictly vanilla-compatible engine without any extra features for levels, suitable for testing FreeDM.

Graphics

Graphics should generally have the same color and size as the original Doom graphics, as to remain compatible with mods. Otherwise, levels may end up looking like a nightmare in design. They may be thematically different as long as it doesn’t clash.

Doom uses a fictional corporation abbreviated as “UAC:” this is trademarked by id Software and cannot be used in Freedoom. Instead, use the initials “AGM” for Freedoom.

Documentation

Freedoom always needs help with documentation, so please send your patches, but keep in mind:

  • We use AsciiDoc for writing the documentation. AsciiDoc is a simple plaintext-based format which is simple to read and write in its source form, and can generate nice HTML documents out of them.

  • Headers are formated in a wiki-style format, this makes it easier for Vim (perhaps other editors, too) to automatically re-format text.

  • Text is kept at 72 characters wide. In Vim, you can set the editor to automatically insert line breaks as you’re typing by performing set textwidth=72. Special exceptions to the width rule might be allowed when necessary (for example, inserting long URLs).

Submitting your work

The most common, and a fairly simple method, to submit your work is by posting it on the Freedoom forum on Doomworld Forums. This allows a great number of people to review the contribution and provide feedback, although the registration process is known to be cumbersome.

An alternative to using the forum, is to post your submission on the issue tracker, which may also be peer-reviewed and provide a feedback cycle.

Lastly, it is possible to get work submitted by joining the official #freedoom IRC channel, although this poses the greatest risk of being lost and forgotten.

Unfortunately, the Freedoom project cannot provide hosting space in the form of a web page nor FTP, however there are many free file hosts to use when you need a location to upload files. Sites and services such as Dropbox and Mega, as well as others, are common and should be simple to use.

Crediting information

Freedoom is made up of submissions from many people all over the globe. All of them, and you, deserve credit! Please do not forget to provide your name and email when submitting resources.

Using Git

You can also commit on a clone of the Freedoom repository, although this is a technical task and it is okay to let other Freedoom maintainers to do it instead: that is our normal mode of operation. However, pull requests are much appreciated and you may submit them in any manner you wish, with GitHub’s direct pull requests being the simplest, but by far not the only means.

Freedoom uses the commit message style commonly seen in distributed version control systems, adopted by projects such as Linux and Git. For an explanation of this style, see How to Write a Git Commit Message.

The commit 2017-02-20T01:52:35Z!mikeonthecomputer@gmail.com is a good example of a properly-written commit.

Do not use commit hashes to refer to other commits. Use other kinds of pointers, simple ones like “my previous commit” might suffice, or use action stamps, which can improve the meaningfulness of commit identifiers if the repository history is rewritten (this has happened at least twice!), or if the repository is converted to another VCS (this happened once before). At the time of writing (February 2017), core Git does not yet have a mechanism to output this format, but you may use a shell script and place it in your $PATH to achieve some ease in generating them.