Reactor is a physics engine from the Irish software company Havok

Havok (company)

Havok is an Irish computer software company that provides interactive software and services for digital media creators in the video game and movie industries....

 for use in Autodesk

Autodesk

Autodesk, Inc. is an American multinational corporation that focuses on 3D design software for use in the architecture, engineering, construction, manufacturing, media and entertainment industries. The company was founded in 1982 by John Walker, a coauthor of the first versions of the company's...

 3D Studio Max

3D Studio Max

Autodesk 3ds Max, formerly 3D Studio MAX, is for making 3D animations. It was developed and produced by Autodesk Media and Entertainment. It has modeling capabilities, a flexible plugin architecture and can be used on the Microsoft Windows platform. It's frequently used by video game developers, TV...

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Overview

Reactor shipped fully integrated with 3ds max from versions 5 to 2011. In 3ds max 2012, Reactor was replaced by a PhysX

PhysX

PhysX is a proprietary realtime physics engine middleware SDK developed by Ageia with the purchase of ETH Zurich spin-off NovodeX in 2004...

-based engine called MassFX. Reactor was often used for realistic physics simulation that would be difficult or time-consuming to animate by hand.

Dynamics types

Reactor is capable of computing rigid body

Rigid body

In physics, a rigid body is an idealization of a solid body of finite size in which deformation is neglected. In other words, the distance between any two given points of a rigid body remains constant in time regardless of external forces exerted on it...

, soft body, cloth and rope collisions, and even all four types interacting with each other. A robust physics engine, reactor can handle several hundred rigid bodies interacting with each other without a problem on most computers. reactor can also simulate dynamics of any supported type interacting with a water volume, including adjustable viscosity and depth, among other things.

Forces and constraints

Reactor includes a large number of forces that can be used in simulation, apart from the default gravity: springs, dashpots, motors, wind, fractures (breakable objects), even a "toy car" type, with definable body/axis/wheels. Reactor also has many constraints available, including hinges, point-to-point constraints, prismatic constraints, car-wheel constraints, point-to-path constraints, and even ragdoll constraints to realistically simulate a lifeless body. In addition, reactor is compatible with Space Warp modifiers in 3ds max