error: no match for ‘operator<<’ (operand types are ‘std::basic_ostream’ and ‘Eigen::Quaterniond {aka Eigen::Quaternion}’)
std::cout << "edge plane quaternion: " << plane_c << std::endl;//plane.unit_quaternion()

想要打印四元数，

std::cout << "edge plane quaternion: " << plane_c.coeffs() << std::endl;

直接打印报错

std::cout << "edge plane quaternion: " << plane_c << std::endl;