Open Source Game Development

Boudewijn Rempt writes "Amazon's recommendation system recommended me "Open Source Game Development: Qt Games for KDE, PDA's and Windows" when I was looking for an introduction to OpenGL. While it does contain two chapters on OpenGL, there's much, much more. It's not just an introduction to writing open source games, it's a complete introduction to participating in open source projects like KDE." Read the rest of Boudewijn's review. Open Source Game Development: Qt Games for KDE, PDAs and Windows author Martin Heni, Andreas Beckermann pages 554 publisher Charles River Media rating 8 reviewer Boudewijn Rempt ISBN 1-58450-406-4 summary Complete guide on writing small to medium games for Linux, Windows and PDA's using Qt.

As maintainer of Krita, the KOffice paint application, I need to know about graphics. Unfortunately, the four months of retraining from sinologist to Oracle Forms developer that launched me into a life of coding didn't include anything on graphics, and certainly not on OpenGL. Which is very much where Krita 2.0 is going.

So... I was looking for an easy introduction to OpenGL to kind of ease my way into the Red and Orange books. And Amazon's weird recommendations system recommended Open Source Game Development: Qt Games for KDE, PDAs, and Windows by Martin Heni and Andreas Beckermann to me. Intrigued, I ordered the volume forthwith. Turns out that that was a good move: this is an excellent book.

In the first place, the text is very clear and concise, but never dry. Forget about the ho-ho-I'm-funny chatty style that's prevalent in many technical books. This book comes to the point immediately. Then, the information is carefully ordered and the presentation very neat and clear. Those would be good points for any book.

But what makes Open Source Game Development: Qt Games for KDE, PDAs, and Windows even more interesting is that it's much more than its title indicates. It is squarely intended at the hobby coder who wants to work on what the book calls "desktop games" -- not the multi-million dollar multimedia productions that demand a new graphics card every half year, but the games that you play while thinking out a knotty problem or that have some educational value for your kids. The kind of project a single coder, or a small team can complete and maintain while still staying sane. And, of course, that kind of game, defender or zaxxon-type games, maze games or tetris-style games work are perfectly suited for pda's and mobile phones, too,

Actually, this book is the perfect introduction to joining a big Open Source project I've seen. Of course, the focus is on Qt and KDE, which means that if you always had this itch to join KDE development but didn't have the necessary skills, this book will help you get there in a very pleasant way.

One way this is done, is by always first giving a general introduction to a topic, and then more detailed discussion in the next chapter. So, first we've got a very good "Qt Primer", and three chapters "KDE Game Development", "Qt Game Development Using Microsoft Windows" and "Game Development and PDA's". And there's a chapter on "OpenGL" in general, and then a chapter on "OpenGL with Qt".

The first part of the book deals with this type of introductory material. The second part discusses "Artificial Intelligence", "Pathfinding" (this chapter was a revelation to me -- I never understood how that worked. If only I had this information while trying to write games for my ZX Spectrum!), "Particle Effects" and "Math and Physics in Desktop Games". The material in these chapters is foreshadowed by the very first chapter "Introduction to Desktop Gaming", which deals with game balancing, architecture and the ins and outs of developing free software. Armed with these chapters, you can add enough game play to your games to make them satisfying to play.

The next three chapters discussion the Qt network classes and how to use them in your games, the KGame library (free software, of course), that contains a lot of boring groundwork that's the same for most games -- players, input devices, network stuff. For me personally, the "XML" chapter wasn't that useful, but then, I'm a corporate cubby-hole programmer by day, and XML is my bread and butter. It's amazing how many billable hours XML can add to a business application project.

A very important chapter, "Open Source and Intellectual Property Rights" makes it very clear what's allowed and what not. The summary chapter, "A Practical Summary" is a novel idea -- at least, I hadn't come across something like this before -- and it works quite well, tying all strands together. There are plenty of references to earlier chapters, so if works like a kind of hands-on index. Not that the actual index isn't top-notch, too.

I should make clear that this book is not just about coding for KDE. That's what most interesting to me, but if you want to code a game for Windows, for a Qtopia or Qt/Embedded environment, then this is the right book. After all, with the release of Qt4 under GPL for Windows (Qt was already released under GPL for X11 and OS X, as was Qtopia), Qt is a good choice for Windows hobby programmers. You get a high quality toolkit that really helps with the boring ground work, and excellent documentation. Coupled with the clear text in this book, there's nothing to hold you back.

Andreas Beckermann is the author of Boson, an OpenGL real-time strategy game based on Qt and KDE. His experience in working on Boson really is apparent in this book. Martin Heni has written a couple of games that that are in KDE's games pack, and has won a prize for his QTopia game Zauralign.

Oh, and the chapters on OpenGL and OpenGL with Qt were enough to make me understand the OpenGL Krita already has and did prepare me quite adequately for the big Red and Orange books. And I've got the itch to write a little game now..."

You can purchase Open Source Game Development: Qt Games for KDE, PDAs and Windows from bn.com. Slashdot welcomes readers' book reviews -- to see your own review here, read the book review guidelines, then visit the submission page.

Comments

Does it answer a really important question?

[Grey Ninja]

How exactly do you make money on open source games? They are a different beast entirely from regular apps. If someone is paying for support for a game, then there's something very wrong going on. I mean, I'm all for open source software, but I've never been able to figure out how to code them, and still put food on the table. As a result, most of my games have been proprietary.

Re:Does it answer a really important question?

[CrazyJim1]

You can make your game opensoure X years later where X years is when you stop making a profit. The reason some of the big dogs don't do this is that they want to resell the game X years in the future in a classics pack. Or rerelease atari 2600 for example. Making a game open source brings more fame to it as more people enjoy mods on your game and your good heart for allowing it to happen, which brings fame to your company. Company fame results in more units sold in the future when you make new games.

Re:Does it answer a really important question?

[ImTheDarkcyde]

not overly true, Quake 4 special edition came with Quake 2. Quake 2 has been open source for some while now.

Making the game opensource does not supply people with the game content, only the engine code :)

Re:Does it answer a really important question?

[linvir]

In conjunction with the closed content/open code trick already mentioned, online games should be very easy to open source. You can easily charge for access to the server for the player's account, instead of for the initial disc purchase.

This flies in the face of the Guild Wars model, but for the WoW model, where you pay for both the disc and the account, it can be amended so that for example, you are forced to buy a certain minimum of months of play.

In my uninformed opinion there really is no reason for paid-account MMORPGs to be closed source. They might say that it's to prevent cheating, but I say that open sourcing would kill cheating dead.

Re:Does it answer a really important question?

[xtracto]

It is quite simple really, and it is the way even some closed games have made money: SAS.

Yeah, the buzzword makes sense for games too, a company could make a game and give away the code while maintaining a good online game community/forums etc. Setup some servers and go!

What I would do is making open source the client, keeping the server, then, let the community improve the client and I would improve the network infraestructure, of course with the client code it would be deadly easy to replicate the server, but there is where the company would have to provide some *special* value on its servers (something like Xbox Live community).

Re:Does it answer a really important question?

[xtracto]

In my uninformed opinion there really is no reason for paid-account MMORPGs to be closed source. They might say that it's to prevent cheating, but I say that open sourcing would kill cheating dead.
--

The problem here is what happened to blizzard and bnetd, but, with an Open Source client it would be trivial to create servers and you wont be doing andy "reverse engineering" thus not breaking the law.

What is needed in these cases is the company to create a "community" with some value in order to persuade people to join. (Certified servers, fast servers, some kind of updates, etc)

Re:Does it answer a really important question?

[modecx]

SAS?

Yes. Isn't it clear enough?

1) The SAS (Special Air Service), Great Britian's answer to the Navy Seals, will send troops to HALO jump straight into the houses of everyone that plays your Open Source game.

2) They will then proceed to ransack the houses of said players, looting any valuables they happen to find, then they will make love to the wives of these game players for no less than a half hour after a romantic dinner at an expensive resturant, and finally they will kill anything that moves before executing a stealthy exit via the Fulton Recovery System.

3) Profit!!!

I like CrystalSpace

[CrazyJim1]

CrystalSpace requires good C++ and 3d skills, but its a very nice open source 3d coding system.

Re:I like CrystalSpace

[Malawar]

Ogre3D is a very nice LGPL 3D Graphics library. It does have precompiled libraries for Windows available for download, but compiling from SVN is a snap as well. While it doesn't have the other parts of a game engine (sound, networking, physics, etc), there's always other libraries that work well with it, such as: The Open Dynamics Engine for physics, OpenAL for sound and SDL for crossplatform network and input. Ogre's visual quality can easily compete with a lot of top game engines today, as well.

Reason?

[xtracto]

Well, I understand this book must be an "introduction" but, I am sure there are several better books on OpenGL, personally I have read the "Beggining OpenGL game programming [Premmier Press]" which I think is quite a nice book if you are new to OpenGL.

I mean, besides of the OpenGL-QT bindings you will have to do (mostly just to create a GL window to render if it is similar to SDL) there is nothing magical in the GL-QT combination. I would recommend to get a nice KDE book AND a nice OpenGL book also, as the author said, besides the blue and red books (which I personally use just for reference . Another great book for OpenGl is the OpenGL Super Bible [Sams], and you can find a bunch of KDE books including the KDE Bible.

Of course if you want to go the "student" way, there is, as I have found, PLENTY of information on all of these topics. Just get into Gamedev.net, the Nehes tutorials are one of the best in my opinion.

Now, if looking for game development I would personally incline to SDL, which will provide you with almost everything you need like input support (joystick, mouse, etc), audio and also OpenGL.

As a last comment, could I ask the SlashDot editors do to their job and check (at least) the book reviews grammar/spelling. My native tongue is not English but it kind of hurted my eyes to read the review (which was quite nice anyway).

Small is good

[Excors]

It is squarely intended at the hobby coder who wants to work on what the book calls "desktop games" -- not the multi-million dollar multimedia productions that demand a new graphics card every half year, but the games that you play while thinking out a knotty problem or that have some educational value for your kids. The kind of project a single coder, or a small team can complete and maintain while still staying sane.

That seems like pretty sensible advice - the phrase "game development" immediately brings to mind the big successful commercial games, but that's not the area in which open source seems capable of competing, and it is much more productive to realise that simple games can be more worthwhile to make.

As for why open source game development has problems when trying to emulate commercial game development, there was some discussion a while back; shamelessly reposting my comment from there:

there are hundreds or thousands of GPL game projects on SourceForge, and most of them are dead

Perhaps the open source idea of havings thousands of eyes, and encouraging anybody to jump in and out of the code making changes, is incompatible with the process of creating a game?

I don't know of any open source applications that are "finished", or even try to be - their early releases are at least slightly useful, and they are always releasing new versions and adding new features. And there always are new features that can be added, each of which will improve the application, so people can work on their favourite features and the project will continue on its path of continual improvement.

Traditional games don't work like that. They're barely recognisable as a game for a large part of their development time - during that time, there has to be a vision for the finished product, and everybody on the project has to work towards that distant vision. It'll be years before anybody can really see the results of their work. That's not very enticing for somebody who can only be certain of spare time for the next couple of months - they would rather work on something much smaller, like a mod or a tech demo, just to get visible results.

And unlike most open source projects, people can't just add features they think are cool and useful - everything has to fit into the overall design of the game. You cannot simply add features without considering the consequences on the whole of the rest of the game - and you can't consider all the consequences unless you've already spent months working on the game and getting a feel for how everything interacts.

For professional game development companies, they get people working towards the vision by simply paying them to do so. That won't work for community-based open source projects, so they need some other way of doing it.

But I don't know what way that would be. I've been working on a "freeware, hobbyist" game instead (0 A.D.), which is a full 3D RTS with its own game engine, comparable in scope to commercial games (or at least to those of a few years ago) - it's making use of various open source libraries (SpiderMonkey, Vorbis, Xerces, etc), but is not itself open source. And I think that's a factor in how it has kept going for so long: 'membership' is still open to anyone who has the right abilities and dedication, but that means there is a strong concept of membership - we're part of a team and feel some responsibility towards making progress, following the design, and seeing the game through until it's finished. I don't think that feeling would be as strong if we were primarily a loose community of people who are just poking around the code with no commitment, which is how I perceive most open source projects.

And programmers are only a small part of game

Re:Small is good

[xtracto]

there are hundreds or thousands of GPL game projects on SourceForge, and most of them are dead
There are 22141 games listed in SourceForge.
Of those, 575 (2.59%) are INACTIVE,
7637(34.5%) are in PLANNING.
6022(27.1%) are in PRE-ALPHA.
4302(19.43%) are in ALPHA
4453(20.1%) are in BETA
3592(16.2%) are in PRODUCTION-STABLE
460 (2.0%) are in MATURE.

Which does not add to 100% because some games have more than two states, however it seems there is a really high trend towards "Unfinished" games. Or as I read from some game developing book, EVERYBODY can have a good game idea, but it takes some hard effort to actually implement it, and it takes really hard nuts to finish it.

And as you said, a game is in fact FINISHED, not like said, OpenOffice, which will never be "finished", with games you can only make bugfixes, but a new game version is something completely different.

Re:Linux Games (SDL, OpenGL)

[xtracto]

I will tell you the main problem in a word: CONTENT.

For some strange reason, software developers enjoy giving away their work/time without expect anything in return, but please tell any decent designer, sound fx creator or graphics drawer to give away their time just "for fun" and you wont get really a lot.

In that way, open source will NEVER compete against the big studios. The only "hope" is to make people look at less "graphic intensive" but more "fun" and innovative games. With a bit of luck, Nintendo will aim that way, but I do not have much hope

If you're considering writing an OSS game

[Trogre]

...then please please PLEASE first take a look at the hundreds of other OSS games out there and consider building on (read: contributing to) one of those.

It's sad looking at the large number of games that have shown promise but for one reason or another have been abandoned or development has slowed or forked. We really don't need another nethack clone, MMORPG or 3D engine. We have all of those in abundance. What we need now is to build on these, both with shader code and good content. It's often easy to tell the OSS games from the commercial ones from a single screenshot because the commercial studios have good artists and the OSS devs don't (I am being overly broad here and there are exceptions such as Frozen Bubble, but these are rare).

One not-quite example: I am a fan of the excellent OSS flight simulator FlightGear. The latest version 0.9.10 has some nice ground textures and real-world data that makes for a truly beautiful view when flying at 30,000 feet. But the planes themselves look like crap. The model detail and decals are average but what really lets it down is the way the plane interacts with light. The engine is badly need of work to take advantage of OpenGL shaders. And the sky looks completely wrong. As you ascend beyond 50,000 feet you should see the sky darken to a very deep blue with some stars becoming visible but the engine doesn't allow for this (you're basically inside a big solid-blue sphere). Not vital properties for learning to fly a 747 I know, but still important polish for a realistic flying experience.

If you have a truly original idea then by all means start from scratch if nothing existing fits the bill, but don't just fire up a text editor and start another MMORPG from scratch. The OSS gaming community don't need it.

Re:Linux Games (SDL, OpenGL)

[LocoMan]

I think it has some to do with the subjectivity in the artists side. Or at least that's how it seems to me (3D animator with basically no coding skills other than the ocassional script in maya).

Coding is a very creative process, however, most of the times the results can be masured objectively. If you're making a 3D engine, you can measure how many polygons per second it moves. If someone makes a change, you can measure if it's faster and/or slower, and exactly by how much.

The same doesn't happen that often in the art side. Let's just say I create the animation of a character swinging a sword. Then someone else comes and changes the animation and makes it completely different. Suposedly both are within the parameters of the game (how long it is, the starting and ending poses), how do you define which is better?. Maybe for the other guy his animation is a lot better than mine, but for me maybe mine was better and his hurts my work (to put it in a way). Most of the times there's just not a real measurement of quality when it comes to the art side.

This is one reason (IMHO) that the artists tend to be less of a group workers than coders. Usually in 3D animated series and movies, for example, you can have hundreds of animators working at the same time, but in most of the cases each scene is animated by a single animator, and if there are several, they don't overlap (one animator does one single character on the scene, or in the case where two animators work on the same character one will do the main animation and the other the secondary movement).

In the coding side it just seems to be "ok, here's what I did, let's fix it, or try to fix it"... in the art side it seems to be more of a "ok, here's what I did, tell me what's wrong but DON'T fix it, I'll fix it myself".

Or at least that's how it look from this side of the monitor.

Re:Linux Games (SDL, OpenGL)

[miyako]

I have done both programming and 3D modeling/animation professionally. I still do 3D work and graphics design on the side, as well as contributing code to F/OSS applications. While I'm a decent programmer, I don't really have experience writing 3D engines or related code that would be useful to many open source games. Many times, if I come across a game that seems interesting and I would like to contribute, I offer to contribute artwork.
What I have found, and it is really a strange thing to me, but many projects simply do not want to accept contributions from artists. There have been a few projects that I've stepped into the mailing lists or IRC channels for and asked "hey, great game. I'm interested in contributing some artwork to the game, anyone have any ideas of things that might be particularly useful?" or simply looked at what was needed and gotten back "we don't need any more artwork/artists". A lot of times the art in these games is either bad, or a mixed bag of decent stuff and terrible stuff (not that no open source games have good artwork, but more that if a game has enough good artwork then I'm more inclined to offer to contribute to a project that seems like they could really use the contributions).
Another thing I've noticed is that one of the big goals of a lot of open source games is to be able to run on older hardware. This isn't necessarily a bad thing, but it does mean that it limits the quality of the artwork. Many commercial games are released when even a top-of-the-line gaming rig can barely get top performance, while many open source games tend to be written to run on any machine built in the last 5 or 6 years. I'm sure part of this is that not ever open source developer can afford a top of the line machine with two bleeding edge video cards (because buying one video card every 6 months for $500 wasn't draing PC gamers wallets enough apparently, they had to invent SLI) and a couple of gigs of ram.
What would be nice is some sort of site like sourceforge but for creative commons licensed artwork that open source games could make use of.