The Common Elements of Vehicle Simulations

People play with flight simulators for one of two reasons. Either they want to experience the joy of flight in a variety of different aircraft, to see how the planes or helicopters look and perform, or they want to fight in aerial combat. In effect, they want to fly aircraft in either civilian or military roles, and that's how we refer to these roles here.

Just as flight simulators tend to fall into military or civilian categories, driving simulators tend to fall into organized racing and imaginary racing categories. Organized racing simulators try to reproduce the experience of driving a racing car or motorcycle in an existing racing class: Indycar, NASCAR, Formula 1, and so on. Like sports games, they require a license to use the official name and indicia of the racing organization. Imaginary racing games are just that: games about racing in imaginary situations, driving madly through cities or the countryside or even fantasy environments.

The vehicle-simulation market is sharply divided between the purists and the casual players. The purists demand highly accurate simulations of real vehicles with all their quirks and limitations. If a purist forgets to retract the flaps after takeoff, he wants those flaps to be damaged by excessive airspeed and to be stuck in the down position, with appropriate consequences for the plane's handling characteristics. The casual players don't care about the details as long as they can fly or drive around fast and (depending on the game) shoot at things.

An Extreme Case

The takeoff sequence in the game Megafortress had to be the longest for any consumer-level flight simulator ever made. The game simulated a hypothetical stealth-modified B-52 bomber. This is what you had to do to get the plane off the ground (fortunately, it was already lined up on the runway):

Switch on battery power.
Switch on interior lights.
Switch on power to all eight engines.
Fire starter cartridges for all eight engines.
Switch off battery power after the engines are running.
Switch on navigation lights.
Switch on landing lights.
Pressurize the plane to noncombat levels.
Tune radio to correct frequency (this also served as the game's copy protection).
Lower flaps.
Release brakes.
Throttle up all eight engines (fortunately, this could be done simultaneously ).
Pull back on stick. (Plane takes off.)
Raise landing gear.
Raise flaps.

This sequence involved moving back and forth from the pilot's seat to the co-pilot's seat a couple of times, too. Soon after you got into the air, you had to switch all the lights back off to avoid detection by enemy aircraft. If you forgot to pressurize the plane, the crew would complain of being cold. When you entered into combat, you were supposed to lower the air pressure to avoid a violent decompression if the plane was hit.

Megafortress was a techno-geek's dream. It was not, however, a big financial success as flight simulators go.

The Rules

Some vehicle simulations aren't games at all, in the sense of being a contest or a competition. Their only goal is to let the player experience controlling the vehicle, so they don't have any rules other than the laws of physics. Most vehicle simulations, however, are set in a competitive context, either a race or a battle of some kind.

One factor to consider is how you want to handle damage. Lightweight racing sims don't simulate any damage at all; if the car hits something, it simply bounces off, which tends to slow it down. This allows the driver to be much more careless. She can afford to hit a few things and still win the raceat least in the earlier, easier stages of the game. Other games model damage as a single variable, such as hit points in a role-playing 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).

Accurate modeling of damage requires dividing the vehicle into areas, determining which area has been damaged by a collision (or, in a military simulator, by enemy fire), and deciding 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 will force it to halt. With airplanes, the consequences can be dramatically different depending on what has been hit. A plane is still flyable if its tail has been destroyed , but it will be unstable and extremely difficult to handle.

Competition Modes

In military flight simulators, the competition modes are similar to those of first-person shooters: solitaire against artificial opponents, multi-player death matches (every player for himself), and team-based play. Civilian flight simulators usually have only a solitaire mode, although they can also allow races and follow-my-lead competitions. Driving simulators are generally solitaire games or multi-player races, and are seldom team-based.

Both military flight simulators and organized race-driving simulators often include a career mode, in which you create a pilot or driver and follow his career (trying not to get him killed , of course), racking up victories and collecting performance statistics. They also include campaign modes, in which a race driver tries to win in a real racing circuit, collecting points according to the official rules of the circuit.

In military flight simulators, the campaign mode can work in various ways. In one approach, the game offers a series of missions one at a time in which the player must achieve a specified victory condition before going on to the next mission; completing all the missions constitutes winning the campaign. In another approach, the player can play all the missions in order, whether she meets the mission objectives or not. However, if she plays through all of them without achieving enough mission objectives, she loses the campaign. This more closely approximates what happens in a real war. The better you fight on any given occasion, the more chance you have of winning the war in the long run, but you can still afford to lose the occasional battle. But as the designer, you have to provide clear feedback to the player about how she's doing as she goes along.

Gameplay and Victory Conditions

The primary challenge in any vehicle simulator is in controlling the vehicle: learning to speed it up, slow it down, and steer it to where you want it to go without crashing it into something. In the case of flight simulators, you can make this challenge simple, requiring the player to know almost nothing about aerodynamics, or extremely difficult, modeling the behavior of an airplane accurately. Unlike a car, airplanes respond rather slowly to their controls, often beginning to execute a maneuver several seconds after the player has first moved the yoke or joystick. Because players are more used to driving a car, they will tend to overcontrol the plane: Finding that it doesn't respond immediately, they'll push the stick farther and then wildly overcompensate in the opposite direction when the plane finally does much more than they intended in the first place. If you want to present a realistic challenge, you can model this problem accurately.

In driving simulators, the chief challenge is staying on the road without crashing. Without being able to feel the G-forces on his body, the player has to depend on other cues to determine how fast he is going and how hard he is braking.

Military Flight Sims

In military flight simulators, the player must not only fly the aircraft, but also achieve the mission's objectives, usually attacking enemy aircraft and ground installations. Modern air-to-air combat, conducted with long-range guided missiles and often directed by Airborne Warning and Control System (AWACS) planes, is something of a chess gamea rather cerebral exercise. Hence the continuing popularity of World War I and II flight simulators and fictional ones such as Crimson Skies (see Figure 13.1). These let the players dogfight: twisting and turning through the sky, hiding behind clouds, diving out of the sun, and blasting away with bullets at short range. It's a much more action-packed experience.

Figure 13.1. A pilot's view in Crimson Skies. Note the very simple instrument panel.

graphics/13fig01.gif

The gameplay in military flight simulators is defined by the role of the aircraft being simulated. Fighter planes are designed primarily to attack enemy aircraft and to protect friendly aircraft and ground units from air attacks. Attack planes are designed to attack moving ground targets; bombers are designed to attack stationary ones. Most military flight simulators offer a series of missions, often with primary and secondary objectives; achieving them constitutes victory. The objectives are usually to shoot down enemy fighters or to destroy ground targets, all without being shot down yourself, of course. Being killed or having your plane shot down constitutes a loss. You can also rate the success of a mission according to the number of objectives achieved, the length of time it took, and the amount of damage sustained by the aircraft, assigning extra points for a swift and safe return.

Civilian Flight Sims

Civilian flight simulators such as the venerable but excellent Microsoft Flight Simulator (see Figure 13.2) seldom have any victory conditions, unless they implement racing or specific challenges, such as tests of speed and accuracy. Many of them are not really games in the competitive sense at all; their goal is to let the player fly and try different things with the aircraft rather than to present him with a specific mission to accomplish. However, civilian flight sims can present a wide variety of challenges: flying at night; flying in rain, fog, or strong winds; and using visual flight rules or instrument flight rules. Landing smoothly and safely, particularly in adverse weather conditions, is always the most dangerous moment in a flight and usually represents the toughest challenge that a civilian flight simulator has to offer. Most of them provide an autoland function that simply returns the plane to the ground without the player having to land it

Figure 13.2. An instrument panel in Microsoft Flight Simulator 2002. This is a game for serious pilots.

graphics/13fig02.gif

Racing Sims

Organized racing simulations, like sports games, take their gameplay from the real thing. The challenge is primarily to win races without crashing. Some games also include an economic element: The player wins prize money for doing well in a race, and the prize money enables her to buy better equipment. This produces positive feedback that must be counteracted to balance the game; as the player improves , her artificial opponents must also improve to offer her a worthy challenge.

Setting

The settings of flight simulators consist of the plane itself and the ground that it flies above. With a few exceptions, such as Microsoft Combat Flight Simulator , most flight sims don't offer interesting terrain. If your flight simulator has a historical setting, you can do a lot on the ancillary screens to set the mood. Electronic Arts' World War II flight simulator, Jane's World War II Fighters , shows a hanger full of period aircraft and other gear, and it even plays Glenn Miller tunes in the background. Unfortunately, in the pursuit of historical accuracy, Electronic Arts set 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 was superb; it's too bad they weren't depicting something more interesting. Its competitor, Microsoft Combat Flight Simulator , was less historically accurate but more fun to fly around because you could 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. Off-road driving offers 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 .

Weather is a critical factor to consider in 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 the drivers need to make a pit stop to switch to rain tires, which hold the road better. The pit stop takes time, but if they don't do it, they run an increased risk of crashing.

Because flight and driving simulators rarely show other people, their worlds can seem eerily devoid of life. Cities are depicted as collections of buildings with no pedestrians and (in flight simulators) no vehicles. Airports have only one plane, the player's, and no ground staff. Simulator designers often feel that because these things aren't critical to the gameplay, they're a waste of time to implement. Still, they add considerably to the sense of immersion.

Interaction Model

The interaction model in a flight simulator is quite straightforward: The player's plane is his avatar. The plane's controls are mapped onto the computer's input devices, and the player's view is normally that of the pilot, forward through the cockpit windows .

Perspective

As with sports games, flight and driving simulations frequently offer a variety of camera perspectives. Although the game is not playable from all of them, they can be used for taking dramatic screenshots or instant replays of action.

Views Common to Driving and Flight Simulators

Both driving and flight simulators implement certain standard views:

Pilot's/driver's view. This is the "normal" view that most simulators offer by default. The player sees what the pilot or driver would see from that position in the cockpit or driver's seat. The vehicle's instruments take up the lower half of the screen, and the view out of the windshield is shown in the upper half, often partially obscured by parts of the canopy or the nose of the car or plane. Most sims offer separate "look left," "look right," and "look backward" views, as well as a mode in which the player can swivel the view smoothly through 360 as well as up, to see what's overhead, and down, to see instruments located below the pilot's normal line of sight.
Cockpit-removed view. This is an unrealistic but dramatic perspective in which the pilot or driver's view out of the front of the vehicle is shown full-screen rather than being partially obscured by the cockpit. Critical instruments are shown as semitransparent overlays in the corners of the screen, so as not to interfere with the view too much. Even these can be removed, providing an unobscured view of the world outside, with no visible indication that the player is in a vehicle at all.
Chase view. This is an exterior view of the player's vehicle, as if from another one following closely behind and mimicking its movements. In flight simulators, the plane always seems to be level and the world turns around it. For example, if the player banks her plane, the horizon tilts while the player's plane appears to be level in the middle of the screen. In driving simulators, the chase view is usually somewhat elevated so the car does not obscure the player's view of the road in front.
Rear, side, and front views. These are exterior views of the player's vehicle from all four sides. If the player's plane banks, the view does not bank; the ground remains below.
Free-roaming camera. Used only in an instant-replay mode, this enables the camera to be moved anywhere in the world and tilted or rotated to look in any direction. This view is useful for players trying to analyze exactly what happened in a particular encounter.

Views Unique to Flight Simulators

The following views are found only in flight simulatorsand military ones, at that:

Ground target view. This is a view of a target on the ground that is currently selected for attack. The camera is positioned at a nearby ground location, facing the target, and does not move. This view lets the player watch incoming missiles or bombs arrive and see if they hit the target accurately.
Bomb or missile view. This is the point of view from a recently released bomb or missile, as if it had a camera in its nose (many modern weapons do). This allows a particularly dramatic perspective as the weapon approaches its target. This view usually disappears after the weapon detonates, and the perspective returns to the default view.

Views Unique to Driving Simulators

The following views occur only in driving simulators. Obviously, the cars are not drivable from these perspectives, but they are great for instant replays.

Trackside view. Many racetracks have cameras located at fixed points around the track. The camera can be either locked to a specific viewpoint or made to track the player's car as it moves past. It's also common to have a routine that switches from one trackside camera to another to follow the leaders as they go around. This gives a good simulation of watching television coverage of a race (see Figure 13.3).

Figure 13.3. A typical trackside view in NASCAR Racing 4.
Grandstand view. This is the traditional spectator's view of the finish line.
Blimp view. This is a high aerial view looking straight down onto the racetrack or course, letting you see all the cars at once.

User Interface Design

The biggest challenge in designing the user interface of a vehicle simulator is in mapping the vehicle's real controls to those available on the target machine. For serious simulations, analog controls are essential; the binary D-pads of older handheld controllers don't allow the kind of precision needed for accurate steering. It used to be that serious simulations simply weren't possible on console machines, but now that most console machines offer analog joysticks, mapping the controls of a race car to those of a home console machine isn't quite as much of a problem.

Force-feedback joysticks, throttles, control yokes, steering wheels, and pedals (rudder for planes, and gas and brake for cars) all help immensely, and serious players will have them. You can greatly improve the quality of the simulation experience for such players by supporting them. However, don't designand, more important, don't tuneyour game with a presumption that your players will have this kind of hardware. It should be an enjoyable experience even with only a standard console controller or a mouse and keyboard. If it's not, you've severely limited your audience and your game is bound to be slammed in reviews.

Military flight simulators always require some simplification from the real thing; you will have to decide how much. Real military aircraft are flown only by special people who have had months or years of training, much of it spent sitting in classrooms. Because we want our players to be able to fly the planes within a few minutes of installing the software, we have to make considerable compromises in the realism of the game. You will almost certainly want to reduce the number of instruments in the cockpit and the number of functions that some of them perform.

One common simplification that almost all flight simulators make is to produce automatically coordinated flight. Ordinarily, the pilot of an airplane must coordinate the movements of the ailerons and rudder when turning, to prevent the plane from skidding sideways in the air, in the same way that a car skids sideways on wet pavement if it takes a turn too fast. Because the plane has no tires gripping pavement to control the direction it is facing, this can happen easily. However, most players have only one control mechanism, the joystick. To simplify flight, the left-right motion of the joystick controls both the rudder and the ailerons simultaneously, producing automatically coordinated flight.

Another common simplification for flight simulators is made in the navigation. Modern planes have global positioning systems, but World War I and II pilots still needed to know proper navigation, plotting their courses by the stars at night and by landmarks or dead reckoning during the daytime. Because this isn't the most exciting thing about flying, just give the player a map.

The Player's Role

The player's role in a flight simulator seems as if it should be quite straightforward: It's that of a pilot. In single-seat aircraft, that's all that is required. However, if you're going to simulate larger aircraft, such as bombers or two-seat fighters, you'll have to decide how you want to handle the varying roles available. In LucasArts' excellent World War II simulator Their Finest Hour, the player could play any of the waist and tail gun positions of the Junkers JU-88 bomber while leaving the plane on autopilot, or he could set the guns to fire automatically at any target that came into view. To drop the bombs, however, he had to take over the bombardier 's position personally . Three-Sixty Pacific's game Megafortress required the player to manage no fewer than five different stations : pilot, co-pilot, navigator, electronic warfare specialist, and offensive weapons officer. Each had its own instrument panel and responsibilities, and the player had to move constantly from one to another to check on conditions and respond to emergencies. At times when the player was away from the pilot's seat, the plane flew on autopilot toward the next waypoint .

In racing-oriented driving games, the player's role is that of a racing driver most of the time, but the more serious simulations, such as Indycar Racing , also allow the player to be a mechanic , modifying the angle of the airfoils, changing tires to compensate for weather conditions, and so on.