I want to know
math::Matrix<3, 3> Rvis = q.to_dcm();
math::Vector<3> v(1.0f, 0.0f, 0.4f);
// Rvis is Rwr (robot respect to world) while v is respect to world.
// Hence Rvis must be transposed having (Rwr)’ * Vw
// Rrw * Vw = vn. This way we have consistency
visionhdg = Rvis.transposed() * v;
this code meaning.