const matn<T,3>& get_inverse_mat3() const { if( !m_inv_cache.is_valid() ) m_inv_cache = m_quat.conjugated().rot_matrix(); return m_inv_cache; }
const matn<T,3>& get_mat3() const { if( !m_cache.is_valid() ) m_cache = m_quat.rot_matrix(); return m_cache; }