Query regarding face pose axis visualisation

[shubhamwagh]

I see that to construct rotation matrix(R) from yaw, pitch and roll angle values, you use zyx order i.e Rz * Ry * Rx,
where Rz is rotation about z-axis, Ry is rotation about the y-axis, and Rx is rotation about the x-axis.

But for visualisation, it looks like the order you use is xyz i.e Rx * Ry * Rz and then use column vectors of this resulting matrix as axis coordinates (https://github.com/thohemp/6DRepNet/blob/master/utils.py#L54). May I know why this is done? Am I missing something?

Thanks.

[thohemp]

The order of the rotation matrix is actually XYZ: https://github.com/thohemp/6DRepNet/blob/master/utils.py#L207

[chwoong]

Dear @thohemp
Thank you very much for providing a great demo :)
It was very helpful.

https://github.com/thohemp/6DRepNet/blob/master/utils.py#L207
I think you got the rotation matrix using pitch-yaw-roll order.
However, https://github.com/thohemp/6DRepNet/blob/master/utils.py#L54
It looks like roll-yaw-pitch order. (see how x3 and y3 are defined. They are independent on roll).

Did I think something wrong? (@shubhamwagh)
Thank you.

[shubhamwagh]

@chwoong yes exactly.