Physics and Game Development; or, What Goes Up Better Come Down

Unless you're making a text-only game, you'll need to apply some form of Newtonian physics to pretty much every action that occurs on the screen. Computer and video games apply the laws of physics so that objects "behave" as they do in the normal world. This means that programmers need to know the physical science equations to apply them accurately and appropriately to the game code. (Even objects in an "alternate" or cartoon universe have to follow the rules of physics to be believable.)

The online book description for Physics for Game Development states, "Colliding billiard balls. Missile trajectories. Cornering dynamics in speeding cars... By applying the laws of physics, you can realistically model nearly everything in games that bounces around, flies, rolls, slides, or isn't sitting still, to create compelling, believable content for computer games, simulations, and animation."

Game elements that require application of physics include things we take for granted in the real world, like elasticity, light, sound, reactions and interactions, and especially gravity.

· Collision detection – Used to determine how two solid objects interact in the envrionment. This could be as simple as whether your avatar walks through a fence or over it, whether you go around an NPC or through her, and whether you can shoot through rocks or not (applied as "line of sight.")

· Particle systems - A common aspect of computer games are explosions. Early computer games used the simple expediency of repeating the same explosion in each circumstance. However, in the real world, explosions vary depending on the terrain, altitude of the explosion and the type of solid bodies that come in contact with the explosion. A particle system model allows a variety of other physical phenomena to be simulated, including smoke, moving water, precipitation, and so forth. An environment's realism is limited by processor power, the knowledge of the programmers and of course, time and money available to make it fancy.

· Ragdoll physics - A procedural animation and simulation technique that displays the movement of a character when it drops to the ground, usually when it's killed. The character's body is a series of rigid bones connected with hinges at the joints; simulations model what happens to the body as it collapses to the ground. More sophisticated physics models of creature movement and collision interactions require greater level of computing power and a more accurate simulation of physical principles and elements. Programmers need to understand how physical principles in the environment affect anatomy—and they also need to be able to communicate really well with artists!

· Cartoon physics – We're all familiar with hapless characters who fun off a cliff and continue to move horizontally until they realize that oh no! there's not more ground and down they go. Sonic the Hedgehog moves at superspeed, characters survive being crushed by a heavy safe and just about any object can endure the classic "squash and stretch" process. These physical anomalies are intended to provide humor and create improbable situations for superheroes. While we don't necessarily want to see them in Call of Duty, we would feel cheated if they didn't show up in a cartoon or superhero-based game.
 

The bottom line is that while you might be able achieve these important (and expected) game elements without a knowledge of physics, the quality and believability of your product would probably not support a high level of art, action and story without them. Without the appropriate application of physics in a computer or video game, you might as well be attacking creeping coins or going through a maze of twisty little passages. As Alice said, "What is the use of a book without pictures . . .?"

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[1] Pertaining to the laws developed by Sir Isaac Newton (1642-1727).

[2] http://www.amazon.com/dp/0596000065/?tag=stackoverfl08-20

[3] Carroll, Lewis. Alice's Adventures in Wonderland.