Part Two: Gameplay Applications of Physics

Except for games where physics provide the main gameplay mechanism, physics has been essentially used in games for cosmetic purposes. Even today very few games use physics to improve their gameplay. The reason for this is simple. Mass-market games like action games are already very demanding in terms of computing power and we have seen that physics is especially demanding in that area, and strongly impacts other parameters such as real-time display.

Today, a more intensive use of physics is conceivable, regardless of the kind of game -- but for what purpose?

In my opinion, there are four groups of application:

• To give the player new ways to handle the challenges he or she will face in the game

• To create mobile game environments

• To develop powerful learning mechanisms

• To allow the player to build his own tools

Providing the gamer with new tools

For most games, the idea behind the gameplay is: 1) offer the gamer a challenge to overcome, such as defeating a group of enemies and 2) provide him or her with tools to succeed: weapons, animations, background elements etc. The gamer's objective is to learn how to master such tools and use them wisely to overcome the challenge.

From this perspective, any new "tool" that is offered to the gamer should enable him or her to achieve this objective. The same is true for physics. If it does not provide new ways for the gamer to overcome the challenge, it is completely useless from the gameplay perspective.

This tough reality should always be taken into account, for the use of physics remains highly demanding in terms of resources and implies significant decisions at the beginning of the project. Let's now look at a few ways to really take advantage of physics to improve gameplay.

Action games represent a major genre, so let's look at the possible uses of physics in action gameplay. In this kind of game, the gameplay lies essentially on the challenges of combat and movement. Physics should therefore provide the gamer with new tools to respond to the following problems:

• Weaken or eliminate opponents

• Protect himself or herself

• Open or close a passage

• Detect opponents

• Hide from opponents

When the gamer's purpose is understood, numerous practical applications come to mind:

• The destruction of background elements enables the gamer to reach an opponent from an advantageous point, gain protection by building a cover, open new paths or on the contrary, close existing paths.

• Fluid management offers a totally new scope. Fluids may be either liquid or gaseous. They allow the player to light up a fire or let the wind blow it in right direction. The smoke generated by the player's actions may impair his opponents' vision, thus offering new tactical opportunities. A moving or expanding liquid may drastically affects the physics of the other bodies: certain bodies will sink, while other will float to the surface. Filling up or, on the contrary, emptying an area may also drastically change the combat and movement conditions and provide a totally new gameplay in an area previously already exploited. A moving fluid may also serve to carry an odor, thus widening the means of detection available for the gamer… and his or her opponents.

Non-static game environments

Today, almost all game levels are totally static. It is the opponents that animate them. Let's imagine games where the game environment itself is the opponent, or at least provides changing conditions. Physics allows for changing environments, with all the consequences: falling objects, loss of balance, objects more or less difficult to move according to the slope, etc.

Imagine an action game that takes place on a sinking ship. Compartments fill with water and change the movement of characters by blocking certain passageways, but also by putting out fires. The angle of the hull itself changes. Large objects can slide along the decks and be used as obstacles or even weapons. The complete change of the ship's angle, such as a turn around or passage to vertical, could lead to a drastic change of the circulation in the hull.

Other situations are imaginable: Fire, earthquake, tidal wave, bombing, sea storm, changes in gravity or space pressurization etc.

It is in fact what we did with CTF-Tornado. The tornado behaves as the "third team", by helping or putting at a disadvantage one of the two sides. The tornado changes the circulation in the map by blocking or opening numerous passageways. Its simple presence prevents the gamers from taking the shortest passageways. It also changes the defense conditions of the map by tearing off pieces of walls or roofs. It can even sidetrack gamers' projectiles!