A physics engine is a computer program that simulates Newtonian physics models, using variables such as mass, velocity, friction and wind resistance. It can simulate and predict effects under different conditions that would approximate what happens in real life or in a fantasy world. Its main uses are in scientific simulation and in video games. A computer program is a collection of instructions that describe a task, or set of tasks, to be carried out by a computer. ... Classical mechanics is a model of the physics of forces acting upon bodies. ... For other uses, see Mass (disambiguation). ... This article is about velocity in physics. ... For other uses, see Friction (disambiguation). ... Wind resistance is overall drag on a body due to its interaction with the atmosphere. ... It has been suggested that simulation software be merged into this article or section. ...

Description

There are generally two classes of physics engines, real-time and high precision. High precision physics engines (or dynamic simulations) require more processing power to calculate very precise physics and are usually used by scientists and computer animated movies. In video games, or other forms of interactive computing, the physics engine will have to simplify its calculations and lower their accuracy so that they can be performed in time for the game to respond at an appropriate rate for gameplay. This is referred to as real-time physics. Computer games use physics engines to ensure realism. Realtime redirects here. ... Dynamical simulation, in computational physics, is the simulation of systems of objects that are free to move, usually in three dimensions according to Newtons laws of dynamics, or approximations thereto. ... A computer game is a game composed of a computer-controlled virtual universe that players interact with in order to achieve a defined goal or set of goals. ...

Physics engines have two core components, a collision detection system, and the actual physics simulation component responsible for solving the forces effecting the simulated objects. There are three major paradigms for physics simulation: In physical simulations, video games and computational geometry, collision detection includes algorithms from checking for intersection between two given solids, to calculating trajectories, impact times and impact points in a physical simulation. ...

• Penalty methods, where interactions are commonly modeled as mass-spring systems. This type of engine is popular for deformable, or soft-body physics.
• Constraint based methods, where constraint equations are solved that estimate physical laws.
• Impulse based methods, where impulses are applied to object interactions.

Finally, hybrid methods are possible that combine aspects of the above paradigms. Hookes law accurately models the physical properties of common mechanical springs for small changes in length. ... Soft body dynamics is an area of physics simulation software that focuses on accurate simulation of a flexible object. ... Constraint is an equation that defines a restriction of solutions of an optimization problem to a so called feasible set. ... For other uses, see Impulse (disambiguation). ...

Scientific engines

One of the first general purpose computers ENIAC was used as a very simple type of physics engine. It was used to design ballistics tables to help the United States military estimate where artillery shells of various mass would land when fired at varying angles and gunpowder charges, also accounting for drift caused by wind. The results were calculated a single time only, and were tabulated into printed tables handed out to the artillery commanders. ENIAC ENIAC, short for Electronic Numerical Integrator And Computer,[1] was the first large-scale, electronic, digital computer capable of being reprogrammed to solve a full range of computing problems,[2] although earlier computers had been built with some of these properties. ... For other uses, see Artillery (disambiguation). ...

Physics engines have been commonly used on supercomputers since the 1980's to simulate the flowing of atmospheric air and water, in order to predict weather patterns. This is known as computational fluid dynamics modeling, where particles of air are assigned a force vector, and these combined forces are calculated across vast regions of space to show how the overall weather patterns will circulate. Due to the requirements of speed and high precision, special computer processors known as vector processors were developed to accelerate the calculations. Modern weather predictions aid in timely evacuations and potentially save lives and property damage Weather map of Europe, 10 December 1887 Weather forecasting is the application of science and technology to predict the state of the atmosphere for a future time and a given location. ... A computer simulation of high velocity air flow around the Space Shuttle during re-entry. ... A vector processor, or array processor, is a CPU design that is able to run mathematical operations on a large number of data elements very quickly. ...

Generally weather prediction is still an inaccurate science because the resolution of the simulated atmosphere is not detailed enough to match real-world conditions, and small fluctuations not modeled in the simulation can drastically change the predicted results after several days. Point attractors in 2D phase space. ...

Similar fluid dynamic modeling is also commonly used for designing new types of aircraft and watercraft, and can provide engineers the information that used to be obtained solely from wind tunnel testing. NASA wind tunnel with the model of a plane A wind tunnel is a research tool developed to assist with studying the effects of air moving over or around solid objects. ...

Tire manufacturers use physics simulations to examine how new tire tread types will perform under wet and dry conditions, using new tire materials of varying flexibility and under different levels of weight loading. The tread of a tire or caterpillar track refers to the pattern visible on its circumference that makes contact with the road. ...

Electronics manufacturers use fluid dynamic modeling to examine how cooling air will flow through the computer case, to locate thermal hotspots that may need additional cooling. CPU heat sink with fan attached A heat sink (or heatsink) is an environment or object that absorbs and dissipates heat from another object using thermal contact (either direct or radiant). ...

Game engines

In most computer games, speed of simulation is more important than accuracy of simulation. Typically most 3D objects in a game are represented by two separate meshes or shapes. One of these meshes is a highly complex and detailed shape which the player sees in the game, for example a vase with elegant curved and looping handles. However, for purposes of speed, a second highly simplified invisible mesh is used to represent the object to the physics engine. To the physics engine, the object may be processed as nothing more than a simple tall cylinder. It is therefore impossible to insert a rod or fire a projectile through the handle holes on the vase, because the physics engine does not know the handles exist and only processes the rough cylindrical shape. The simplified mesh used for physics processing is often referred to as the bounding box. Engines that use bounding boxes or bounding spheres as the final shape for collision detection are considered extremely simple. Generally a bounding box is used for broad phase collision detection to narrow down the number of possible collisions before costly mesh on mesh collision detection is done in the narrow phase of collision detection. In computer graphics and computational geometry, a bounding volume for a set of objects is a closed volume that completely contains the set. ...

Screen capture of Sumotori Dreams (freeware physics game)

In the real world, physics is always active. There is a constant brownian motion jitter to all particles in our universe as the forces push back and forth against each other. For a game physics engine, such constant active precision is unnecessary and a waste of the limited CPU power. In the 3D virtual world Second Life, if an object is resting on the floor and the object does not move beyond a certain minimal distance in about two seconds, then the physics calculations are disabled for the object and it becomes frozen in place. It remains frozen until a collision occurs with some other actively physical object, and that reactivates physics processing for the object. This freezing of stable non-moving objects allows the physics engine to conserve processing power and increase the framerate of other objects currently in motion, but can lead to unusual problems such as a huge slow pendulum freezing in place on the upswing, as it slows down and starts to reverse direction. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... Three different views of Brownian motion, with 32 steps, 256 steps, and 2048 steps denoted by progressively lighter colors. ... This article does not cite any references or sources. ... This article is about a virtual world. ...

The primary limit of physics engine realism is the precision of the numbers representing the position of an object and the forces acting on that object. When the precision is too low, errors can creep into the calculations due to rounding, causing an object to overshoot or undershoot the correct position. These errors are compounded in situations where two free-moving objects are fitted together with a precision that is greater than what the physics engine can calculate. This can lead to an unnatural buildup energy in the object due to the rounding errors, that begins to violently shake and eventually blow the objects apart. Any type of free-moving compound physics object can demonstrate this problem, but it is especially prone to affecting chain links under high tension, and wheeled objects with actively physical bearing surfaces. Higher precision reduces the positional/force errors, but at the cost of greater CPU power needed for the calculations.

Another unusual aspect of physics precision involves the framerate, or the number of moments in time per second when physics is calculated. Each frame is treated as separate from all other frames, and the space between frames is not calculated. A low framerate and a small fast-moving object leads to a situation where the object does not move smoothly through space but in fact seems to teleport from one point in space to the next point in space as each frame is calculated. At sufficiently high speeds a projectile will miss a target, if the target is small enough to fit in the gap between the calculated frames of the fast moving projectile. In Second Life this problem is resolved by making all projectiles as if they were arrows; a long invisible shaft trails behind the bullet so that as the bullet teleports forward, the shaft is long enough to cover the gap between successive teleports of the bullet and collide with any object that might fit between the calculated frames.

Physics based character animation in the past only used rigid body dynamics because they are faster and easier to calculate, but modern games and movies are starting to use soft body physics now that it is possible. Soft body physics are also used for particle effects, liquids and cloth. Some form of limited Fluid dynamics simulation is sometimes provided to simulate water and other liquids as well as the flow of fire and explosions through the air. Rigid body dynamics differs from particle dynamics in that the body takes up space and can rotate, which introduces other considerations. ... Fluid dynamics is the sub-discipline of fluid mechanics dealing with fluids (liquids and gases) in motion. ...

Physics Processing Unit (PPU)

February 2006 saw the release of the first dedicated Physics Processing Unit (PPU) from Ageia, called PhysX, which functions in a similar manner to the Graphic Processing Unit (GPU) in a graphics card - off-loading the majority of the physics processing weight off the CPU and into a dedicated processor. The unit was most effective in accelerating particle systems. Only a small performance improvement was measured for rigid body physics. [1] The Ageia PPU is documented in depth in their US patent application #20050075849. [2] A Physics Processing Unit (PPU) is a dedicated microprocessor designed to handle the calculations of physics, especially in the physics engine of video games. ... Ageia, founded in 2002, is a fabless semiconductor company. ... PhysX can refer either to a proprietary realtime physics engine middleware SDK developed by AGEIA (formerly known as the NovodeX SDK) or their PPU expansion card designed to accelerate that SDK. Middleware physics engines allow game developers to avoid writing their own code to handle the complex physics interactions possible... GPU may stand for: Graphics processing unit, a special stream processor used in computer graphics hardware Gosudarstvennoye Politicheskoye Upravlenie (Главное Политическое Управление, or Main Political Directorate) of the Red Army, responsible for troops morale and propaganda. ... CPU can stand for: in computing: Central processing unit in journalism: Commonwealth Press Union in law enforcement: Crime prevention unit in software: Critical patch update, a type of software patch distributed by Oracle Corporation in Macleans College is often known as Ash Lim. ... For more background on this topic, see game physics. ...

An early academic PPU research project^[1][2] named SPARTA (simulation of physics on a real-time architecture) was carried out at Penn State [3] and University of Georgia. This was a simple FPGA based PPU that was limited to two dimensions. This project was extended into a considerably more advanced ASIC-based system named HELLAS. A field-programmable gate array or FPGA is a gate array that can be reprogrammed after it is manufactured, rather than having its programming fixed during the manufacturing — a programmable logic device. ... This article does not cite any references or sources. ...

Academic PPU research projects

Example SPARTA animation Image File history File links No higher resolution available. ...

SPARTA Printed circuit board Image File history File links No higher resolution available. ... Part of a 1983 Sinclair ZX Spectrum computer board. ...

Hellas die photo Image File history File links Size of this preview: 566 × 599 pixels Full resolution (800 × 847 pixel, file size: 181 KB, MIME type: image/jpeg) A die photo of the HELLAS hardware physical modeling chip. ... A die in the context of integrated circuits is a small piece of semiconducting material on which a given circuit is fabricated. ...

General Purpose processing on Graphics Processing Unit (GPGPU)

GPGPU ("General Purpose processing on Graphics Processing Unit") is another promising approach for realtime physics engines, including rigid body dynamics. ATI and NVIDIA provide rigid body dynamics on their latest graphics cards, with ATI claims X1900 XT should deliver 9 X the performance of an Ageia PhysX card- General-purpose computing on graphics processing units (GPGPU, also referred to as GPGP and to a lesser extent GP²) is a recent trend focused on using GPUs to perform computations rather than the CPU. The addition of programmable stages and higher precision arithmetic to the rendering pipelines allowed software developers... In computer science, real-time computing (RTC) is the study of hardware and software systems which are subject to a real-time constraint—i. ... ATI may stand for: ATI Technologies Inc. ... NVIDIA Corporation (NASDAQ: NVDA) (pronounced IPA: ) is a U.S. corporation specializing in the manufacture of graphics processors (graphics processing units, GPUs) technologies for workstations, desktop computers, and handhelds. ...

NVIDIA's GeForce 8 Series supports a new GPU-based Newtonian physics acceleration technology named Quantum Effects Technology - which will compete directly with the PhysX PPU hardware. NVIDIA provides an SDK Toolkit for what they call CUDA™ (Compute Unified Device Architecture) technology that offers both a low and high-level API to the GPU. Few technical details are available about the physics side of it, and it is not yet clear whether this is part of Havok FX SDK, and/or AGEIA PhysX SDK, or a completely separate engine.^[3] NVIDIA Corporation (NASDAQ: NVDA) (pronounced IPA: ) is a U.S. corporation specializing in the manufacture of graphics processors (graphics processing units, GPUs) technologies for workstations, desktop computers, and handhelds. ... The Geforce 8 Series is the eighth generation of NVIDIAs GeForce graphics cards. ... PhysX can refer either to a proprietary realtime physics engine middleware SDK developed by AGEIA (formerly known as the NovodeX SDK) or their PPU expansion card designed to accelerate that SDK. Middleware physics engines allow game developers to avoid writing their own code to handle the complex physics interactions possible... The acronym PPU can refer to: Physics Processing Unit - a dedicated physics microprocessor used in several modern video game consoles. ... This article does not cite any references or sources. ... This article or section does not cite any references or sources. ...

ATI & AMD offer a similar SDK for their ATI-based GPUs and that SDK and technology is called CTM™ (Close to Metal™) which provides a hardware interface thin (thin hardware interface). AMD has also announced the AMD Stream Processor product line (combining a CPU and a GPU technology on one chip). ATI may stand for: ATI Technologies Inc. ... Advanced Micro Devices, Inc. ... A Software Development Kit, or SDK for short, is typically a set of development tools that allows a software engineer to create applications for a certain software package, software framework, hardware platform, computer system, operating system or similar. ... CTM may mean: Community Trade Mark, the European trademark registration system Computational theory of mind, the view that the human mind is best conceived as a computational system Concepts, Techniques, and Models of Computer Programming, a computer programming textbook Compagnie de Transports au Maroc, a formerly state-owned Moroccan bus... This articles Limitations section does not cite any references or sources. ... Advanced Micro Devices, Inc. ... The AMD Stream Processor (previously branded as ATI FireStream) is a stream processor developed by ATI Technologies. ... CPU can stand for: in computing: Central processing unit in journalism: Commonwealth Press Union in law enforcement: Crime prevention unit in software: Critical patch update, a type of software patch distributed by Oracle Corporation in Macleans College is often known as Ash Lim. ... GPU may stand for: Graphics processing unit, a special stream processor used in computer graphics hardware Gosudarstvennoye Politicheskoye Upravlenie (Главное Политическое Управление, or Main Political Directorate) of the Red Army, responsible for troops morale and propaganda. ...

See also

• Game physics
• Ragdoll physics
• Procedural animation
• Rigid body dynamics
• Soft body dynamics
• List of games that rely on physics for their game-play
• Physics processing unit
• Cell microprocessor

Computer animation physics or game physics involves the introduction of the laws of physics into a simulation or game engine, particularly in 3D computer graphics, for the purpose of making the effects appear more real to the observer. ... Early animation using ragdoll physics, from 1997. ... A procedural animation is a method often used in computer and video games to automatically generate animation in real-time to allow for a more diverse series of actions than could otherwise be created by artists. ... Rigid body dynamics differs from particle dynamics in that the body takes up space and can rotate, which introduces other considerations. ... Soft body dynamics is an area of physics simulation software that focuses on accurate simulation of a flexible object. ... This is a list of videogames that feature the use of physics (Classical mechanics in particular) as an important aspect of gameplay. ... A Physics Processing Unit (PPU) is a dedicated microprocessor designed to handle the calculations of physics, especially in the physics engine of video games. ... Layout of the IBM Cell die Cell is a microprocessor architecture jointly developed by a Sony, Toshiba, and IBM, an alliance known as STI. The architectural design and first implementation were carried out at the STI Design Center over a four-year period beginning March 2001 on a budget reported...

Real-time physics engines

Open source

• Bullet
• Open Dynamics Engine
• OPAL
• PAL
• Tokamak physics engine
• Farseer Physics Engine - 2D physics engine for Microsoft XNA and Silverlight

Bullet is an open source physics engine, hosted at Sourceforge. ... A simple vehicle driving over a ramp. ... The Open Physics Abstraction Layer (OPAL) is an open source realtime physics engine API similar to PAL. It was originally supported only by ODE, but should be extendable to run off of multiple engines. ... The Physics Abstraction Layer (PAL) is an open source cross platform physics engine API abstraction system. ... The Tokamak Game Physics SDK is a commercial software physics engine with limited free distribution. ... Microsoft XNA (XNAs Not Acronymed[1]) is a set of tools, complete with a managed runtime environment, provided by Microsoft that facilitates computer game design, development and management. ... Microsoft Silverlight (code-named Windows Presentation Foundation/Everywhere or WPF/E) is a proprietary XAML-based runtime for browser-based Rich Internet Applications, providing a subset of the animation, vector graphics, and video playback capabilities of Windows Presentation Foundation. ...

Closed source/limited free distribution

• Newton Game Dynamics
• Simple Physics Engine
• True Axis
• PhysX (formerly NovodeX and incorporating Meqon)

Newton Game Dynamics is a free, but closed source physics engine for realistically simulating rigid bodies in games and other real-time applications. ... PhysX can refer either to a proprietary realtime physics engine middleware SDK developed by AGEIA (formerly known as the NovodeX SDK) or their PPU expansion card designed to accelerate that SDK. Middleware physics engines allow game developers to avoid writing their own code to handle the complex physics interactions possible... Meqon is a real-time physics engine for computer entertainment software. ...

Commercial

• Havok
• nV Physics SDK
• Vortex from CMLabs Simulations

This article is about the physics engine. ... nV Physics SDK is a new realtime physics engine middleware that is still under development. ...

High precision physics engines

• Mechanica from Parametric Technologies Corporation.
• Working Model, from Design Simulation Technologies. (2D only)
• Falling Bodies, from Animats. (Ragdoll physics)

Early animation using ragdoll physics, from 1997. ...

External links

• Chris Hecker's "Rigid Body Dynamics" tutorial
• Adrian Boeing's physics engine list
• Open Dynamics Engine
• PhysicsAndMathLibrary This library is royalty-free for hobby use and an inexpensive alternative for commercial developers.
• Newton Game Dynamics Newton is a free physics engine for commercial and hobby use, supports multiple platforms, SDK is contained as well.
• PGNX Physics, a versatile physics engine with haptic capabilities
• Bullet Physics Library Open Source, free for commercial use collision detection and rigid body dynamics library.
• True Axis Physics SDK
• DigitalRune Knowledge Base contains a comprehensive list of physics engines and rigid body dynamics resources (master thesis, links).
• Limitations of 3D Physics Engines: Unintended Explosion Google Video demonstration of calculation errors, in the virtual world Second Life.
• Physics2D.Net A 2 dimensional rigid body physics engine written in C#.

Racing physics: This article is about haptic technology. ... The title given to this article is incorrect due to technical limitations. ...

• FastCar Library
• Atlas F1 technical forum
• Racer Free Car Simulation Physics
• Racing Physics and Maths forums at rscnet.org

References