Reactor (software)

Reactor is a physics engine from the Irish software company Havok for use in Autodesk 3ds Max.
Overview.
Reactor shipped fully integrated with 3ds max from versions 5 to 2011. In 3ds max 2012, Reactor was replaced by a PhysX-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, 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.