Code:

//...                //create WorldbtDefaultCollisionConfiguration* config = new btDefaultCollisionConfiguration();btCollisionDispatcher* dispatcher = new btCollisionDispatcher(config);btBroadphaseInterface* broadphase = new btDbvtBroadphase();btSequentialImpulseConstraintSolver* solver = new btSequentialImpulseConstraintSolver();btDiscreteDynamicsWorld* world = new btDiscreteDynamicsWorld(dispatcher, broadphase, solver, config);world->setGravity(btVector3(0,-10,0));//create ObjectbtCollisionShape* shape = new btBoxShape(btVector3(1,3,1));btTransform transform;transform.setIdentity();btVector3 localInertia(0,0,0);shape->calculateLocalInertia(40.0f, localInertia);    btDefaultMotionState* motionState = new btDefaultMotionState(btTransform(btQuaternion(0,0,0,1), btVector3(50,50,50)));btRigidBody* body = new btRigidBody( btRigidBody::btRigidBodyConstructionInfo(40.0f, motionState,shape, localInertia));world->addRigidBody(body);btVector3 position = body->getCenterOfMassPosition();std::cout << position.getX() << " " << position.getY() << " " << position.getZ() << std::endl;for(int i = 0; i < 100; ++i){world->stepSimulation(6,10);position = body->getCenterOfMassPosition();std::cout << position.getX() << " " << position.getY() << " " << position.getZ() << std::endl;}//...

Code:

class World{btDefaultCollisionConfiguration*m_Config;btCollisionDispatcher*m_Dispatcher;btBroadphaseInterface*m_Interface;btSequentialImpulseConstraintSolver*m_Solver;btDiscreteDynamicsWorld*m_World;public:World() {m_Config     = NULL;m_Dispatcher = NULL;m_Interface  = NULL;m_Solver     = NULL;m_World      = NULL;}void init(){m_Config = new btDefaultCollisionConfiguration();m_Dispatcher = new btCollisionDispatcher(m_Config);m_Interface = new btDbvtBroadphase();m_Solver = new btSequentialImpulseConstraintSolver();m_World = new btDiscreteDynamicsWorld(m_Dispatcher, m_Interface, m_Solver, m_Config);m_World->setGravity(btVector3(0,-10,0));}~World() {delete m_Config;delete m_Dispatcher;delete m_Solver;delete m_Interface;delete m_World;}void addObject(btRigidBody* body){m_World->addRigidBody(body);}void update(){m_World->stepSimulation(20,10);}};