Rot3 Quaternion BUG

[HViktorTsoi]

Description

There is an issue when using Rot3().quaternion().x(), Rot3().quaternion().y(), Rot3().quaternion().z(), or Rot3().quaternion().w() to access the components of a quaternion. For example, when using Rot3().quaternion().w() to access qw, it actually returns qz.

Steps to reproduce

Using the flowing code to reproduce the bug:

double qw=0.782240, qx=0.589819, qy=0.199939, qz=0.000000;
std::printf("Correct quaternion:\n");
std::printf(
        "qw: %f  qx: %f  qy: %f  qz: %f\n",
        qw, qx, qy, qz
);

std::printf("\nIn GTSAM Rot3:\n");
gtsam::Rot3 a_rotation(qw, qx, qy, qz);
std::printf(
        "qw: %f  qx: %f  qy: %f  qz: %f\n",
        a_rotation.quaternion().w(),
        a_rotation.quaternion().x(),
        a_rotation.quaternion().y(),
        a_rotation.quaternion().z()
);
std::printf(
        "q[0]: %f  q[1]: %f  q[2]: %f  q[3]: %f\n",
        a_rotation.quaternion()[0],
        a_rotation.quaternion()[1],
        a_rotation.quaternion()[2],
        a_rotation.quaternion()[3]
);
std::printf("\n\n\n\n");

Expected behavior

From the first 2 lines of the result above we can see that, the correct components of the quaternion should be
qw: 0.782240 qx: 0.589819 qy: 0.199939 qz: 0.000000

However, when I construct a Rot3() instance with the quaternion constructor and access the components through the getters such as quaternion().x(), it returns the wrong component(it returns quaternion().w()).

Though using the index I can get the component in the right order(see the last line of the result), where quaternion()[0],[1],[2],[3] corresponding to qw, qx, qy, and qz.

Additionally, after checking the source code, I'm sure the quaternion passed to the Rot3() constructor is correct, as shown below:

gtsam/gtsam/geometry/Rot3.h

Line 121 in 342f30d

Rot3(double w, double x, double y, double z) : Rot3(Quaternion(w, x, y, z)) {}

Environment

1. GTSAM 4.0.2
2. Ubuntu 18.04
3. GCC & G++ 7.5.0

Additional information

[HViktorTsoi]

Update:
Rot3().toQuaternion() will return correct component.

double qw=0.782240, qx=0.589819, qy=0.199939, qz=0.000000;
std::printf("Correct quaternion:\n");
std::printf(
        "qw: %f  qx: %f  qy: %f  qz: %f\n",
        qw, qx, qy, qz
);

std::printf("\nIn GTSAM Rot3:\n");
gtsam::Rot3 a_rotation(qw, qx, qy, qz);
std::printf(
        "qw: %f  qx: %f  qy: %f  qz: %f\n",
        a_rotation.quaternion().w(),
        a_rotation.quaternion().x(),
        a_rotation.quaternion().y(),
        a_rotation.quaternion().z()
);
std::printf(
        "to_qw: %f  to_qx: %f  to_qy: %f  to_qz: %f\n",
        a_rotation.toQuaternion().w(),
        a_rotation.toQuaternion().x(),
        a_rotation.toQuaternion().y(),
        a_rotation.toQuaternion().z()
);
std::printf(
        "q[0]: %f  q[1]: %f  q[2]: %f  q[3]: %f\n",
        a_rotation.quaternion()[0],
        a_rotation.quaternion()[1],
        a_rotation.quaternion()[2],
        a_rotation.quaternion()[3]
);
std::printf("\n\n\n\n");