spatosc

            x(_x), y(_y), z(_z), w(_w)

            {}

        void ToAxis(Vector3 &axis, double angle){

            Quaternion q=(*this).Norm();

            angle=acosf(q.w)*2.0f /*TO_RADIANS*/;

            double sa=1.0f/sqrtf(1.0f-q.w*q.w);