The Bullet physics manual shows that “Bullet Physics is a professional Open Source collision detection, rigid body and soft body dynamics library.” It consists of Open Source C++ code released under the Zlib license and is free for any commercial use on all platforms including Playstation 3, XBox 360, Wii, PC, Linux, Mac OSX and iPhone. A Dynamics World provides a high-level interface that manages physics objects and constraints and implements the update of all objects each frame. For each object, one updates the position of the render object from the physics body using motion states. Function stepSimulation will perform collision detection and physics simulation. Bullet physics simulation runs at an internal fixed frame rate of 60 hertz. If the application delta time is smaller then the internal fixed time step, Bullet will interpolate the world transform and send it to the btMotionState without performing physics simulation.