[tmatrix]

hi, everyone

I'm read the code of sixDoFRigidBodyMotion class recently. There is a function rotate in this class and the details are shown as following:

inline Foam::Tuple2<Foam::tensor, Foam::vector>
Foam::sixDoFRigidBodyMotion::rotate
(
const tensor& Q0,
const vector& pi0,
const scalar deltaT
) const
{
Tuple2<tensor, vector> Qpi(Q0, pi0);
tensor& Q = Qpi.first();
vector& pi = Qpi.second();

tensor R = rotationTensorX(0.5*deltaT*pi.x()/momentOfInertia_.xx());
pi = pi & R;
Q = Q & R;

R = rotationTensorY(0.5*deltaT*pi.y()/momentOfInertia_.yy());
pi = pi & R;
Q = Q & R;

R = rotationTensorZ(deltaT*pi.z()/momentOfInertia_.zz());
pi = pi & R;
Q = Q & R;

R = rotationTensorY(0.5*deltaT*pi.y()/momentOfInertia_.yy());
pi = pi & R;
Q = Q & R;

R = rotationTensorX(0.5*deltaT*pi.x()/momentOfInertia_.xx());
pi = pi & R;
Q = Q & R;

return Qpi;
}

I do not know why five rotations should be carried out? Is there any detailed illustration for these treatments?