1. About the camera pose representation.
The pose of an image is represented as the projection from world to the camera coordinate system. That is, p=K[R|T]X.
Therefore, the coordinates of optical center in world coordinate is not (TX,TY, TZ).
2. How to draw the pyramid?
You can use LineSet in Open3D. Define point(vertex) and connect them with lines(edges).
See here for more information.
3. Can we use cv2.undistortPoints ?
No. The APIs in the camera calibration and 3D reconstruction modules are prohibited.
You have to implement it by yourself if you want to use it.
If you have any question, please send email to 3dcv@csie.ntu.edu.tw