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Game physics

Game physics

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Encyclopedia
Computer animation physics or game physics involves the introduction of the laws of physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 into a simulation
Simulation
Simulation is the imitation of some real thing available, state of affairs, or process. The act of simulating something generally entails representing certain key characteristics or behaviours of a selected physical or abstract system....

 or game engine
Game engine
A game engine is a system designed for the creation and development of video games. There are many game engines that are designed to work on video game consoles and personal computers...

, particularly in 3D computer graphics
3D computer graphics
3D computer graphics are graphics that use a three-dimensional representation of geometric data that is stored in the computer for the purposes of performing calculations and rendering 2D images...

, for the purpose of making the effects appear more real to the observer. Typically, simulation physics is only a close approximation to real physics, and computation is performed using discrete values.

There are several elements that form components of simulation physics:
  • Physics engine
    Physics engine
    A physics engine is computer software that provides an approximate simulation of certain physical systems, such as rigid body dynamics , soft body dynamics, and fluid dynamics, of use in the domains of computer graphics, video games and film. Their main uses are in video games , in which case the...

     is program code that is used to simulate Newtonian physics within the environment.
  • Collision detection
    Collision detection
    Collision detection typically refers to the computational problem of detecting the intersection of two or more objects. While the topic is most often associated with its use in video games and other physical simulations, it also has applications in robotics...

     is used to solve the problem of determining when any two or more physical objects in the environment cross each other's path.

Particle systems



A common aspect of computer games that model some type of conflict is the explosion. Early computer games used the simple expediency of repeating the same explosion in each circumstance. However, in the real world an explosion can vary depending on the terrain, altitude of the explosion, and the type of solid bodies being impacted.

Depending on the processing power available, the effects of the explosion can be modeled as the split and shattered components propelled by the expanding gas. This is modeled by means of a particle system
Particle system
The term particle system refers to a computer graphics technique to simulate certain fuzzy phenomena, which are otherwise very hard to reproduce with conventional rendering techniques...

 simulation. A particle system model allows a variety of other physical phenomena to be simulated, including smoke
Smoke
Smoke is a collection of airborne solid and liquid particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires , but may also be used for pest...

, moving water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...

, precipitation
Precipitation (meteorology)
In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

, and so forth.

The individual particles within the system are modeled using the other elements of the physics simulation rules, with the limitation that the number of particles that can be simulated is restricted by the computing power of the hardware. Thus explosions may need to be modeled as a small set of large particles, rather than the more accurate huge number of fine particles.

Ragdoll physics



This is a procedural animation
Procedural animation
A procedural animation is a type of computer animation, used to automatically generate animation in real-time to allow for a more diverse series of actions than could otherwise be created using predefined animations....

 and simulation technique to display the movement of a character when killed. It treats the character's body as a series of rigid bones connected together with hinges at the joints. The simulation models 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 solids, liquids, and hydrodynamics. The modeled articulated systems can then reproduce the effects of skeleton
Skeleton
The skeleton is the body part that forms the supporting structure of an organism. There are two different skeletal types: the exoskeleton, which is the stable outer shell of an organism, and the endoskeleton, which forms the support structure inside the body.In a figurative sense, skeleton can...

, muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s, tendon
Tendon
A tendon is a tough band of fibrous connective tissue that usually connects muscle to bone and is capable of withstanding tension. Tendons are similar to ligaments and fasciae as they are all made of collagen except that ligaments join one bone to another bone, and fasciae connect muscles to other...

s, and other physiological
Physiology
Physiology is the science of the function of living systems. This includes how organisms, organ systems, organs, cells, and bio-molecules carry out the chemical or physical functions that exist in a living system. The highest honor awarded in physiology is the Nobel Prize in Physiology or...

 components.

External links

  • Game physics resources on GameDev.net
  • Online Physics Games at Phyfun Games
  • Bullet Physics Engine
    Bullet (software)
    Bullet is an open source physics engine featuring 3D collision detection, soft body dynamics, and rigid body dynamics. It is used in games, and in visual effects in movies. The Bullet physics library is published under the zlib license. Erwin Coumans, its main author, worked for Sony Computer...

     is an open source physics engine free for commercial use, including PlayStation 3
    PlayStation 3
    The is the third home video game console produced by Sony Computer Entertainment and the successor to the PlayStation 2 as part of the PlayStation series. The PlayStation 3 competes with Microsoft's Xbox 360 and Nintendo's Wii as part of the seventh generation of video game consoles...

    .
  • DigitalRune Knowledge Base contains a comprehensive list of physics engines and links to game physics resources.