source: code/releases/release2012/src/external/bullet/LinearMath/btDefaultMotionState.h

#ifndef BT_DEFAULT_MOTION_STATE_H
#define BT_DEFAULT_MOTION_STATE_H

#include "btMotionState.h"

///The btDefaultMotionState provides a common implementation to synchronize world transforms with offsets.
struct  btDefaultMotionState : public btMotionState
{
        btTransform m_graphicsWorldTrans;
        btTransform     m_centerOfMassOffset;
        btTransform m_startWorldTrans;
        void*           m_userPointer;

        btDefaultMotionState(const btTransform& startTrans = btTransform::getIdentity(),const btTransform& centerOfMassOffset = btTransform::getIdentity())
                : m_graphicsWorldTrans(startTrans),
                m_centerOfMassOffset(centerOfMassOffset),
                m_startWorldTrans(startTrans),
                m_userPointer(0)

        {
        }

        ///synchronizes world transform from user to physics
        virtual void    getWorldTransform(btTransform& centerOfMassWorldTrans ) const 
        {
                        centerOfMassWorldTrans =        m_centerOfMassOffset.inverse() * m_graphicsWorldTrans ;
        }

        ///synchronizes world transform from physics to user
        ///Bullet only calls the update of worldtransform for active objects
        virtual void    setWorldTransform(const btTransform& centerOfMassWorldTrans)
        {
                        m_graphicsWorldTrans = centerOfMassWorldTrans * m_centerOfMassOffset ;
        }

        

};

#endif //BT_DEFAULT_MOTION_STATE_H