ASM
Building Geo-games
ERIC LEGGE-SMITH, GRANT MCKENZIE and MATT DUCKHAM
Location-based gaming is growing. These are the games in which play centres around players’ geographical movements.
However, the technical challenges facing the developers of these location-based games is inhibiting their commercial success.
Even the simplest location-based games can be great fun. The need for players to move around the game space and explore their environment, at the same time as interacting with other players, makes them immediately engaging and surprisingly addictive.
One only has to look at the vast video games market, worth more than US$10 billion, and the staggering recent growth of online games to appreciate the possibilities for such online games. Just one example, World of Warcraft, now boasts more than nine million subscribers.
The increased availability of low cost PDAs with colour screens and high quality audio, and operating systems that support downloading big files, provide an ideal technological environment for these games. The expansion of broadband wireless networks in many metropolitan areas is also having an impact.
So why are there no notable commercial location-based games available today? The most successful and well known location-based game is geo-caching, in which one uses GPS to hunt for an outdoor treasure hidden by other players.
Geo-caching does not require real time game playing capabilities. Geocachers can download information about caches in advance of playing.
Consequently, part of its success can be attributed to its technical simplicity.
Geo-cachers need only an internet connection at home and an ordinary consumer GPS unit to play.
Credited as the first commercial location-based game, the massively multi-player BotFighters achieved high levels of popularity in its country of origin, Sweden, and in other countries, such as Russia and Finland.
Botfighters is played on mobile phones, and uses the mobile network as a simple positioning system. Players attempt to ‘kill’ other players by firing SMS messages at each other.
The network CGI (cell of global identity) is used to determine the approximate location of players, and whether they are close enough to get a good shot.
Botfighters is a near real time game, but its technical simplicity (players only need a GSM phone to play) has undoubtedly contributed to its success.
Building on these encouraging models, more recent developments in real time location-based gaming include Pac-Manhattan; Human Pacman; and ARQuake.
These games aim to incorporate greater complexity. For example, they combine real time gaming with GPS positioning and use sophisticated AR (augmented reality) interfaces.
However, these more advanced offerings are still largely confined to university research labs. The task of translating them into a commercial environment appears to present substantial technical hurdles.
One of the biggest impediments to next generation, real time location-based games is the complexity of game development. It is hard to join the technologies required for location based gaming into a whole.
This could mean integrating GIS and GPSstyle positioning systems with non-spatial technologies such as wireless communication and mobile devices. Such obstacles apply even when developing a prototype.
In the Geomatics Department at the University of Melbourne we recently developed a prototype location aware mobile game, called GISnake.
It is based around the popular 1980s arcade game, Snake. In our version, the player or players to move around a real geographic area, collecting apples.
Collecting apples increases a player’s score, as well as the length of a player’s tail. If players cross another player’s or their own tail, they lose the game. The aim is to achieve the highest score possible
In GISnake, the geographic play area is real. But the apples and the players’ tails are virtual, and are only displayed on their mobile computers or PDAs. Each player’s visual displays are continually updated via a wireless communication network. They reflect changes in their own and other players’ tails and positions as shown in the sequence of screenshots.
Even for our prototype, which used heavier laptops as mobile devices, this game works remarkably well and can be good clean fun. Racing around the city, dodging other pedestrians, finding the best route through the streets to collect all the apples, and devising strategies to box in your opponents with your lengthening tail, all make for excellent game play. Part of the appeal of the game is that it can be played anywhere: your local neighbourhood, a busy city centre, parkland or open spaces.
The characteristics and constraints to movement imposed by the different game environments lead to some exciting experiences.
However, the technical challenges facing even such a relatively simple prototype are formidable. Yet the overall architecture is conventional enough.
GPS is used to determine the geographic position of each player (mobile client). Using software on the mobile client, each player’s latest position is relayed back to the game server every few seconds via the internet. This is done using either WiFi where available, or the mobile phone network.
The game server integrates a number of components: scripting utilities such as tools to parse NMEA strings and project co-ordinates; a map server to produce maps of the player’s immediate vicinity; and a spatial database for storing the player’s current locations and tail.
It also carries a game engine that contains the game logic and rules of the game, and a web server to communicate the latest game data in a form that can be displayed by any web-enabled mobile device.
An additional objective in developing GISnake was to use free and open source software for the different components as far as possible. The web server is Apache; the database mySQL; the scripting language PHP; and the map server was originally UMN MapServer (with Google Maps API later tested and used). The entire game server runs on a Linux PC.
Each of the components in this architecture is, on its own, simple enough to understand and customise. However, the primary technical challenge of developing location based games is in integrating these components in such a way that very near real time results can be returned to the user.
Even relatively short delays dramatically affect the playability of the game. Users have to stop and wait to see if they have eaten the apple, bumped into an opponent’s tail, won or lost. There are many common map server solutions, but there was a period of trial and error before we settled on one that was fast enough for the game (using Google Maps API).
Some of the technical challenges arose from the diversity of mobile client devices (laptops, tablet PCs, PDAs, mobile phones) common today. This appreciably complicates client software development. Other challenges are explicitly spatial.
The level of accuracy and precision of low cost GPS, particularly in urban gaming environments, means that unfiltered GPS data can lead to game errors.
For example, unfiltered GPS errors in early versions of the GISnake prototype would mistake stationary players as moving and even crossing their own tails. To make the game playable, carefully tailored position filters were created to minimise such errors. Yet it still needed to be able to discern small enough player movements to make the game exciting.
The game logic can also be surprisingly difficult to construct. Designing exciting multi-player games is a complex task. The process is especially challenging for location-based gaming, where the game itself is played in a geographic space.
When developing GISnake, the development process included an intermediate stage that used a game simulator.
Using this tool, the development team could test out aspects of GISnake at their desks by moving ‘virtual players’ around a simulated game.
However, in the later development phases team members needed to physically leave their desks and offices to test the game. Although this process can be fun, it is also time-consuming and labour intensive.
Despite these challenges, the experiences with GISnake showed us that it is possible for a small team to develop a sophisticated location-based game prototype. But the levels of technical expertise required are very high.
However, new standards and development tools are emerging for LBS and location-based gaming. Ericsson’s increasingly popular mobile positioning system (MPS) software development kit is one example. As a result, today’s technical problems will be tomorrow’s plug in components.
Our experiences show that even relatively basic location based games can be compelling and enjoyable. By helping to address some of the spatial aspects of the technology, spatial information science has a real chance to contribute to what may soon grow into a multi-billion dollar industry.
