typename ForceDense<Derived>::Vector3 operator* (const ForceDense<Derived> & phi)
{
typedef typename ForceDense<Derived>::Vector3 Vector3;
return Vector3(phi.linear()[0], phi.linear()[1], phi.angular()[2]);
}
typename ForceDense<Derived>::ConstAngularType::template ConstFixedSegmentReturnType<1>::Type
operator* (const ForceDense<Derived> & f) const
{ return f.angular().template segment<1>(axis); }