q_L and q_R typo in math_utils.h ?

[narutojxl]

Hi @hyye thanks for your excellent work :)

• The rotation convention in your code is Hamilton, correct?
• q_L and q_R matrix in math_utils.h is JPL?

Thanks for your help!

[hyye]

Hi @narutojxl, Thanks for your question. The conversion is all in Hamilton as Eigen's.

[narutojxl]

In joan's paper, his rotation is also Hamilton. In math_utils.h

template inline Eigen::Matrix<typename Derived::Scalar, 4, 4> LeftQuatMatrix(const Eigen::QuaternionBase &q) { Eigen::Matrix<typename Derived::Scalar, 4, 4> m; Eigen::Matrix<typename Derived::Scalar, 3, 1> vq = q.vec(); typename Derived::Scalar q4 = q.w(); m.block(0, 0, 3, 3) << q4 * I3x3 + SkewSymmetric(vq); m.block(3, 0, 1, 3) << -vq.transpose(); m.block(0, 3, 3, 1) << vq; m(3, 3) = q4; return m; } The code doesn't consistent with above definition?

[hyye]

I think it is exactly the same, except the order of the quaternion, right?

[narutojxl]

q_L in code is:

joan q_L is:

I don't understand why they are the same, right? :)

[hyye]

Since the orders of the coefficients are different. If you swap q_v and q_w, these two matrices are the same, right???

[narutojxl]

Hi @hyye, thanks for your patience with me :), thanks a lot !

• I see the eigen doc about quaternion's vec() function. It returns the imaginary part(q_x, q_y, q_z), matching joan's quaternion definition(q_w is scalar part, [q_x, q_y, q_z] is imaginary part).
• x(), y(), z() return the x, y, z coefficient respectively of quaternion. w() return the w coefficient.