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07/03/2010 0 A.D. Open Source Release
Published: 10 July 2009 Contents:
About 0 A.D.
OS release
What is 0 A.D.? Why care?
Reasons
0 A.D. is a free, cross-platform,
Organisation
under-development, 3D,
Code
historically-based, real-time Reusability
strategy game. Comparisons
Getting started
What are you doing?
Switching from a closed development
process to open source: making the
code available as GPL and the art
content available as CC-BY-SA, and
encouraging external contributions.
We've been working on 0 A.D. in our
free time for years, and now we want
to show what we've achieved and
make it easier for more people to get
involved.
0 A.D. is a very complex and
ambitious project. A lot of work has
been put into it, but a lot remains to be
done. We're not releasing a playable
game – you'll have to wait until much
later if that's what you're interested in.
There are plenty of major missing features and bugs and rough edges. We're
releasing this as a work-in-progress, pre-alpha project, aimed at developers
who might be interested in this kind of thing, in the hope of sharing resources
with a community that would otherwise be excluded from our development
process.
This is an experimental step and we don't quite know what's going to work
best, so we're going to move carefully and try to adapt based on experience.
This document describes our current plans; feedback will be appreciated!
Contact us on our forums, or #0ad on QuakeNet IRC.
Why should I care?
We think there's a good chance we
can produce a pretty decent game
with some unique features. Maybe
you want to help that game come into
existence.
Maybe you want to learn from the
experience of working on a complex
software project, or particularly on a
game. There's a wide range of areas
involved: graphics and audio, AI and
UI, file handling and gameplay
scripting and networking and so on.
The basic framework is all in place,
and some of it is already very solid,
but there's a lot of scope for diving into
the details and working on various
components.
Maybe you want to make the game work better on your favourite platform.
Maybe you want to show us how stupid we are and how you can write code
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that's much better. (We're far from perfect!)
Maybe you want to use parts of our code or art in your own project. Maybe you
want to use our game for teaching a practical game development class. And
maybe you have other reasons.
Why are you doing this?
We've been working on this game in
some form or another since 2001.
We've come a long way since then,
but making this kind of game is really
quite hard. The original team
members were largely students, and
have now moved on in life and can't
devote much time to the project.
Attracting new developers is difficult
and time-consuming – few people
have the time and skill to learn how to
work within our existing code and to
make significant contributions. So we
want to lower the barriers to entry,
making it easy for people to check out
our project and see if it interests
them, in the hope that some will decide it does.
Also, we have some ideas and tools and code that we think are quite nice
and would like to share. We ought to clean them up and document them
properly so they're more useful to other people, but making the code available
is the first step. And, particularly on Linux, open source simplifies a number of
issues with distribution and debugging, so it makes things easier for us and
for users.
Up until now, access to the project has been limited to 'official' members of
our group, though the intent has always been to produce a non-commercial
game and membership has always been quite open. The concept of open
source simply wasn't considered interesting a couple of years ago, but times
have changed and it now seems the natural way to develop our project.
How is the development
going to be organised?
In opening this project, we need to
respect the community by providing
as much information and
communication and support as
possible, so you can benefit from
participating in the project (hopefully
contributing back and benefiting us, of
course!), balanced with our desire to
get the game completed to a high
standard and with some constraints
from our past organisation.
In the past, all developers have been
part of the official 'team': anyone can
apply to join, we'll have a short
interview over IRC to get to know them, and if it seems they have the time and
energy and skill to contribute usefully then they're made a member. We're
going to keep the core group of developers and the private communication
methods – we don't want to risk destroying the team we've already got. We're
going to keep aiming towards a particular design vision, and we don't want to
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diverge much from that – we'd rather not add (and have to maintain) features
that aren't part of that goal. We're releasing the art and gameplay data for two
of the game's six civilisations, but holding back the work-in-progress civs until
they are more complete and usable.
Apart from those restrictions, we're opening access to the source control
server (Subversion), and the documentation and issue-tracking system
(Trac), and moving our technical discussions to an open forum. Anyone can
download, build and run the latest version of the game. Our initial process for
contributions will be very basic: If you make some changes, you should
create a patch and submit it to us, and we should then review it and maybe
suggest some changes or commit it to SVN.
Licensing of contributions is an open question. On one hand, accepting GPL
code would guarantee to contributors that we're not going to unfairly use their
work. On the other hand we'd like to keep our options open by only accepting
BSD-licensed code, perhaps to produce a special version linked with
proprietary cheat-detection software to discourage multiplayer map hacks
that would be trivial to add to an open-source game, or to link with proprietary
digital distribution systems to get more widespread distribution. The ideal
solution is not clear, so we'd be interested in discussion of this issue.
What is the code like?
There's roughly 150K lines of C++ for
the game engine, and another 25K for
editing tools. Gameplay scripting
uses JavaScript. We build on top of
low-level libraries (OpenGL, OpenAL,
ENet, ...), not an existing game engine
(like OGRE).
The code isn't all extremely clean or
extremely modular or extremely well-
written. It's been written by a wide
variety of programmers, and it's far
from a "completed" codebase. We
want to continue cleaning things up
as part of the normal development
process. We're not averse to rewriting
entire subsystems if that's the most
effective way to make them satisfy our requirements. But in many areas it's
quite solid.
What reusable code is there?
Most of our code is specific to the game and not very useful outside it, but
some parts could perhaps be interesting for developers working on other
projects. Some examples:
Low-level library providing cross-platform support for resource
management (archive file loading, GL textures and shaders, ...),
debugging tools (error reporting, memory tracking, stack dumps),
timers, asynchronous IO, allocators, ...
Converter from COLLADA models with skeletal animation into a
simple game-friendly format.
Binary XML caching system, for faster resource loading.
Automated build tools using Amazon EC2.
Boring maths code for matrices, vectors, quaternions, etc.
How does this compare to other games?
We are aware of several other open-source RTS games. Glest has reached
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'stable' status and is set in a medieval/fantasy world, with less complex
gameplay and graphics but with AI opponents (which are not yet
implemented in 0 A.D.). ORTS is a framework emphasizing AI research more
than a playable game. Spring is another RTS engine that appears designed
for gameplay similar to Total Annihilation. 0 A.D. is striving to differentiate
itself by providing new gameplay ideas, detailed graphics and an an accurate
historical setting.
How can I get started?
See the Getting Started guide to find more information about the game,
forums for discussion, instructions for building and running the game, and
links to further details.
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