template <class T> class VertexLock
{
public:
    // Locks object vertex data with specified lock mode.
    VertexLock( T* obj, T::LockType lock ) :
        m_obj(obj)
    {
        obj->lockVertices( lock );
    }

    // Unlocks object vertex data.
    ~VertexLock()
    {
        m_obj->unlockVertices();
    }

private:
    T* m_obj;    // note! this must be weak pointer because otherwise all models must be allocated to heap

    VertexLock();
    VertexLock( const VertexLock& );
    VertexLock& operator=( const VertexLock& );
};