Core Mechanics

Designing a vehicle simulation is primarily a matter of research and compromise. Unless your game is a just-for-fun simulation such as Super Mario Kart or Beetle Adventure Racing!, vehicle simulation is the most technologically oriented of games, so the core mechanics of the game are almost entirely about physics. Much of the entertainment value of accurate simulation games comes from the feeling of controlling a real machine instead of meeting strategic challenges or taking part in a story. To provide that value, you will need to research your vehicles thoroughly.

If you’re designing a military vehicle, you can probably find much of what you need from Jane’s Information Group, publishers of such volumes as Jane’s All the World’s Aircraft, and of course, from the vehicle’s manufacturer. For automobiles, the various enthusiast magazines offer all the data you could want.

The compromises occur when you start trying to control a simulated vehicle with a computer or console machine’s I/O devices, especially a large, complicated vehicle such as a B-52 bomber. The kinds of compromises you make and the places they take you will depend mostly on whether your target audience is the purist or the casual player.

Designing Opponents

The easiest way to design a variety of opponents in a vehicle simulation is simply to provide different drivers’ vehicles with different performance characteristics. One plane climbs slightly faster than another; one can turn more sharply. The player will experience different challenges in dealing with each opponent based on its design parameters. However, once the player figures it out, the opponent is easily beaten. As soon as the player discovers that a Supermarine Spitfire can consistently outrun a Messerschmitt Bf 109 in level flight, the situation offers an obvious strategy for Spitfire pilots: boom and zoom (hitting and running away).

To create further variety, modify the behavior of individual opponent drivers (or pilots). Design the AI for these opponents by starting with perfect performance and then creating variations from perfection. For example, it’s possible to create a “perfect” AI driver in a racing simulation, one that always follows the most efficient line around the track, always shifts gears at precisely the correct moment, and knows the ideal speed at which to take each corner without spinning out. If such a driver has a better car than the player’s, she will be unbeatable. The trick, then, is to modify the AI driver’s judgment so that it isn’t perfect—so that she doesn’t always shift at exactly the right time or follow the most efficient line. This combination of factors, both vehicle characteristics and variable driver skill, provides the variety among opponents in vehicle simulators.

As you research flying or driving, you will discover other tricks to incorporate in the AI: drafting behind other cars, for example, and diving out of the sun to surprise the enemy in a dogfight.

In addition to letting the player compete against artificial opponents, it’s also useful to let him compete against his own performance in a prior race or time trial. The simplest form of this is simply to keep a record of his times and let him try to beat them, but it’s also fun for him to see a ghostly version of his own car from the earlier race as he drives. To do this the software will need to record all the details of the player’s driving—where the car was, how fast it was going, and so on—throughout each race, so it can use that data to implement the ghost. You will probably be doing this anyway to provide an instant replay feature, and it helps with debugging and tuning as well.

Damage

You need to decide what to do about damage. Comical or arcadelike racing sims may not simulate damage at all; if the car hits something, it simply bounces off, although doing so usually slows down the car. This allows the driver to be much more careless, and it is a good solution for casual and children’s games. They can afford to hit a few things and still win the race—at least in the earlier, easier stages of the game. Other games model damage as a single variable, like unit health points in a war game. When damage reaches a certain level, the vehicle simply stops running (which, in the case of an airplane, means that it crashes or explodes). If your target machine doesn’t have much CPU power (as in a cell phone, for example), these approaches mean you don’t have to model the physics very accurately.

To model damage accurately, you should divide the vehicle into separate areas that can suffer damage in a collision (or, in a military simulator, from enemy fire), and decide how that damage affects the performance of the vehicle. For instance, a race car with minor damage to the airfoils or body can continue, although with a performance penalty, but a blown tire forces it to halt. With airplanes, the consequences can be dramatically different depending on what part of the aircraft sustains damage. A plane can still fly without its tail, but it is unstable and extremely difficult to handle. These approaches give great verisimilitude but require sophisticated physics models to accomplish.

The Game World

The landscape that a simulated vehicle moves through is an important part of the game’s entertainment—even if it’s a relatively static landscape as in a racing game—because the landscape is connected with the function of the vehicle itself.

The settings of flight simulators consist of the plane itself and the ground that it flies above. If your flight simulator has a historical setting, you can do a lot with the ancillary screens to set the mood. Electronic Arts’ World War II flight simulator, Jane’s WWII Fighters, shows a hangar full of period aircraft and other gear, and even plays Glenn Miller tunes in the background. Unfortunately, in the pursuit of historical accuracy, Electronic Arts sets all its combat missions above the Ardennes Mountains in the wintertime: a bleak, snowy landscape covered with leafless trees. The technical quality of the graphics is superb for its day; it’s too bad they aren’t depicting something more interesting. Its competitor Microsoft Combat Flight Simulator is less historically accurate but arguably more fun to fly because you can buzz the Eiffel Tower or London’s Houses of Parliament.

Driving simulators are set on either racetracks or roads, except for a few off-road simulators that offer the fun of bouncing all over interesting terrain without having to steer carefully. Narrow, twisting mountain roads are a popular choice for road-based games because they offer both an interesting challenge and pretty scenery. Players also enjoy driving around in replicas of real cities with landmarks that they can recognize, if you have the time and budget to implement them.

Weather is a critical factor to consider when designing the settings of both flight and driving simulators. Can the player drive or fly at night? In rain? In fog? Rain plays an important strategic role in automobile racing because each driver needs to make a pit stop to switch to rain tires, which hold the road better. The pit stop takes time, but drivers who don’t take the time run an increased risk of crashing.

Because flight and racing simulators rarely show other people, their worlds can seem eerily devoid of life. Cities are often depicted as collections of buildings with no pedestrians (and in flight simulators, no vehicles). Each airport has only one plane—the player’s—and no ground staff. Simulator designers often feel that, because these things aren’t critical to the gameplay, it is a waste of time to implement them. Still, they add considerably to the player’s immersion. A World War II airfield should have other planes, pilots, and ground staff moving around; a track-based racing sim should certainly have a crowd in the grandstand. Imaginary driving games such as The Simpsons: Road Rage or Crazy Taxi are more likely to include pedestrians because they are hazards to avoid.