Karting games are usually a bit - well, let’s not mince words - crap. They rarely take the sport seriously, feature anything approaching decent physics, or even deliver quality racing. However, Melbourne based developer Zach Griffin is out to change that with an enormously ambitious and promising looking project called KartSim (official site). The game will eschew arcade antics and instead deliver in-depth, serious karting action for fans of the sport.

Griffin has been working away on the game for over five years now, but with KartSim approaching its beta release, we figured it was time to have a look at this promising independent project.


Firstly - why a game looking at kart racing, when so many other forms of motor sport are more popular with players and have a bigger profile?

Zach: If you look at games like the Gran Turismo and Forza series and indeed the majority of racing titles on the market, they all give the player the opportunity to unlock and drive cars that they might not have the chance to in real life. That's always going to be a major attraction for gamers and car enthusiasts alike, for sure.

However, once you get past that, the core racing experience can be quite dull. This is inherent with mixed class racing and wide open circuits. That's not something you can ever accuse kart racing of being; drivers have to navigate a corner every 3-5 seconds whilst racing at speeds of up to 160km/h right on the bumper of another competitor. That's why you've seen guys like Schumacher, Alonso and Senna back in a kart during the F1 off season.

Does that mean I'm saying KartSim is more fun that those other titles? Absolutely. It's hard to go back to them after playing KartSim!

What attracted you to karting specifically?

Zach: I've watched F1 since 1996 and you always hear of karting being referred to as the sport which taught all the drivers their race craft. Once I finished school, I started racing myself and experienced the excitement of karting first hand in the super tough Clubman Light category. I had always wanted to make a racing game and made initial designs back in 01', so it was only natural that I combined the two...

What is the single most challenging aspect when looking at making a kart racing game compared to other forms of motor sport?

Zach: Simulating the vehicle dynamics of a kart is by far and away the most challenging aspect of developing a kart racing game. Despite their simple appearance (and from a mechanical point of view, they most definitely are); a kart's non-rigid chassis means the mathematical assumptions you can make about a standard vehicle's chassis (i.e a Formula 1 monocoque) can't be used.

This complicates the physics model as you are no longer dealing with a rigid-body. The drive train model is the same from a physics point of view as a full sized car. I'll spare you the intricate details of what that actually means, but basically a kart is a lot more complex to simulate than a standard vehicle. Given the option of simulating an F1 car or kart I'd choose the F1!

So how have you simulated the different way karts handle - as they don't have a differential and so rely on the inside wheel on the back axle to lift so that the tyres don't scrub and bind up?

Zach: It's an interesting challenge. Of course most games that feature karts have typically just used the same physics model as a car, with tuned suspension settings and a locked differential which will never be right. KartSim uses the Finite Element Method (FEM) to simulate the kart chassis flex alongside its steering geometry model.

This allows the stiffness of the chassis and other parameters like the caster angle, kingpin inclination and tie rod length to be entered into the simulation. The end result is a kart that lifts the inside rear wheel when turning around a corner from all the chassis forces at work. The great thing about this is depending on how much rubber is down on the track, the kart will flex differently forcing players to adjust their setup to match the conditions.

Tell us about your real time FEM model?

Zach: I can't say much about the specific implementation, as there was a lot of effort put into solving the design challenges created by the requirement for it to be real time. What I can say is that it basically treats the chassis as a matrix of equations that when solved, allows forces generated from the tyre to be input and the resultant chassis deflection amount output.

Sounds like there’s a lot of mathematics involved! Try and give us a simple overview of what you were trying to achieve?

Zach: The objective with the physics was quite simple; to be as realistic as possible with no compromises. That means being able to put real data into the simulation and have the performance of the simulated kart match the recorded telemetry. To achieve that goal was exceptionally complex with many hours spent reading academic and industry white-papers on topics ranging from tyre dynamics and polymers, through to generic vehicle dynamics and physics.

Of course, I also had to read many mathematics books on topics ranging from 3D geometry to calculus. Let's just say there is a use for all that maths you learnt in school!

Some of the maths involved

Development tools must be a challenge when working with such unique parameters. Tell us about the Unity engine and the sorts of changes you had to incorporate to make it work for you?

Zach: The Unity tool set is a game engine that handles things like rendering, input, and audio whilst also providing a framework to program your own game logic. The great thing about using an engine like Unity is it allows a developer to concentrate on game specific features rather than having to integrate yet another low level API into their own engine for a basic feature like input.

It's also in a constant state of development so it's always evolving and supports the Xbox360, PS3, Wii and the mobile platforms. That's not to say it's all been smooth sailing; the inbuilt networking was not at all suitable for an online racing game which needed to support 30 other players. That meant I had to write the dedicated server and client from scratch. That said, I'm yet to see another current engine with a better work flow so I'll keep using it for the time being.

Which tracks and classes do you plan on featuring in the game, and how do these differ in terms of the on-track experience for the driver?

Zach: The tracks and classes are yet to be announced, although each circuit and class brings something different to the game. The circuits offer a mixture of tight, fast, flowing, and technical driving experiences, whilst the kart classes cater for those who want to have close racing at slower speeds in midget/cadet classes, to those who want to race at the fastest speed possible like your Formula 100 or KF1 classes.

Karts are massively responsive to steering input and can be quite tricky to drive smoothly. How have you balanced the physics needs of the simulation with the all important imperative that the karts feel realistic, but are still fun to drive?

Zach: The great thing is the karts have always been fun to drive despite it being a simulation. You can throw them around quite a lot or be smooth, so it inherently caters for different driving styles. That said, the exceptionally small steering angles can be quite a challenge for someone who plays a lot of car racing games and are used to driving bigger cars where you need to turn the wheel a lot.

For the upcoming multiplayer beta, the setup of the kart is fixed for all players and has quite a soft front end which makes the steering a little more forgiving by sacrificing how direct the kart is.

Which circuits are you featuring and how did you go about creating these accurately? I note on the website Asian, European, Middle Eastern and USA circuits are featured...

Zach: Each circuit with the exception of Oakleigh, which was plotted using GPS survey technology, has been laser scanned to generate a 3D point-cloud and allows a circuit to be recreated with millimeter accuracy. On board telemetry from a lap is recorded and thousands of photos are also taken which are used for texture sources. Once the circuit is in the game, the telemetry is used to verify the performance of the kart on the circuit to ensure the accuracy of the simulation.

Kart engines also have quite unique sound. Tell us about the method you used to generate the engine noise?

Zach: Currently the sound is sample driven, which means sounds are recorded from the specific engine on a dyno at varying RPM levels. Once in game, a mixture of the recorded samples is played back depending on the simulated RPM level. The end result is an engine which sounds exactly like its real life counterpart.

A big part of the karting experience for any racer is their love for the unique handling properties of the brand of chassis they drive, and to date you have featured the popular Arrow brand of chassis in the game. Have you looked at incorporating any other types of chassis? Will each model, even those within the Arrow range, handle differently?

Zach: We haven't yet announced the different brands of chassis that will appear in the game, but yes KartSim will feature most of the major kart brands. As to the different handling characteristics; each kart will need to be setup a little differently, yet have the same level of potential performance.

Different weather and tyre wear conditions are the two most significant on track changes a driver must adapt to. How are you including them in your design?

Zach: KartSim simulates both these elements, with varying weather patterns and tyres that wear differently depending on how you drive. Players will have to keep an eye on the sky for rain in the game as well as be aware of how they are using their tyres. Harder compound tyres can be pushed quite hard, with the softer compounds needing a lot more care.

What sort of racing are you looking to have in the final product?

Zach: Circuit racing is the primary category for the final product, but I'm also looking at other types of racing for future expansions; notably oval and dirt racing as they are quite different to the norm. Superkarts are also something that may make an appearance in the future.

How is the beta process coming along?

Zach: It's progressing quite well, with only a short list of bugs to fix and final features to implement. I've setup a great testing team which means the end product should be reasonably bug free. I'm also currently setting up the global network of servers which store the data for each player as well as other services like the In-Game Advertising and player skin systems.

How many karts on track? How will you look to manage the rules for a rolling start? As you know all kart races start this way.

Zach: KartSim supports up to 30 karts on the track, which can be quite intense particularly at the start of a race. The rolling start code had to be extremely robust, as there are a huge number of variables to track whilst operating autonomously. It's part of a much larger system that also manages grid positions, lap times, whether the grid gates are open or shut, penalties for track cutting and yellow and blue flags amongst others.

The end result is a system that could quite easily run a real life race meeting without the need for any human control. At the start of a race, each competitor is monitored for their speed and position as well as the distance to the vehicle ahead. Players are also shown who they must follow which can change depending on whether someone leaves the server, goes back to the pits or even just pulls over on the side of the track.


What sort of online play options are you evaluating?

Zach: The current online format follows that of a club day; one 5 minute practice session followed by 3 x 8 lap races with a short break in between each session. This really intensifies the online experience as no longer does it take over an hour to cycle through one round like the other racing titles out there.

This is something that online shooters picked up on years ago if you look at games like Counter-Strike and to a lesser extent the Call of Duty and Battlefield series. Players of racing games don't want to be sitting around practicing for 50 minutes to take part in a 5 minute race which is where the fun is. Keeping it short and fun is the key to making a player think "just one more race". Before they know it, they've said that five times!

Have you considered looking at including handling and setup options for more experienced drivers? Will it be possible to tweak tyre pressures, tuning and other aspects like different axles, ride height and different compound metals in the wheels and other components?

Zach: Setup options will appear in the full game. If you're a kart driver, you'll feel right at home with all real-life setup options available. Everything from track width, front bars, gear ratios, exhaust length through to seat position, front end geometry and tyre pressures is able to be changed. Of course if you're a gamer who is new to the genre there's also information about what changing each option does to the handling."

How are you looking to bring the game to the market? Has it been a hard road to get such an ambitious project to the masses?

Zach: Absolutely! I now know the reason that AAA titles have US$50+million dollar budgets and 60+ people working on them. I can literally count the number of days over the past 5 years on my hands that I haven't worked on the game. Also, like any other start up venture, making the game has to be something you must be passionate about and love to do.

No one particular area that has been difficult. Programming a simulation game with multiplayer racing and web services to support it all is quite a complex task alone, before you tackle the commercialisation tasks of corporate structures, accounting, legals and marketing. Couple that with building and moderating an online community and fan base and it soon escalates into a huge project. I'm currently in talks with a number of different investor groups to get things moving a bit quicker. At the moment it's like being a Lamborghini without the fuel.

As for bringing the game to market post-beta, the marketing and distribution strategy will see KartSim sold through traditional retail channels and online digital marketplaces (i.e. Steam and Origin) with some cool guerrilla marketing campaigns. Coupled with the future expansion onto the Xbox360 and PS3 platforms should see KartSim ranked up amongst the current house-hold name racing titles.

The game has been five years in the making - if you could go back and start the development process now, knowing all that you do, what would you now do differently in making the game?

Zach: It's an interesting question. Since last April I've actually rewritten the entire game from scratch so I'd definitely impart the knowledge of the need to do that to my younger self! There will also always be things little things that you could have done differently. As for a major mistake, I haven't hit any serious speed bumps yet and we are working to make the game as good as possible for the beta!


What has been the one aspect of the game so far that people have been most positive about?

Zach: The attention to detail both in terms of graphics and the physics model. Whilst both of those elements definitely help with getting people excited about the game, we've got the gameplay to keep them excited.

What do you think is the coolest thing you have done so far?

Zach: The off-track experience is something I'm quite proud of and a feature that I hope becomes a legacy in future racing titles. As for what the off-track experience actually is, you'll have to wait for the beta!

Thanks very much for speaking to games.on.net, Zach, and best of luck with the beta release!