rvec/tvec from cv::calibrateCamera and R1 from cv::stereoRectify

Question

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Exact definition of the matrices in OpenCv StereoRectify

1. What is the camera frame of the rvec and tvec calculated from the cv::calibrateCamera? Is it the original (distorted) camera or the undistorted one? Does the camera coordinate change when the image is undistorted (not rectified)?

2. What is the R1 from the cv::stereoRectify(). To my understanding, R1 rotate the left camera coordinate (O_c) to a frontal parallel camera coordinate (O_cr) so that the image is rectified (row aligned with the right one). In other word, apply R1 on the 3D points in the O_cr will result in points in the O_c. (or is it the other way around?)

Few posts and the OpenCV book tried to explain it, but I just want to confirm that I understand it clearly. As the explanation of rotating image plane is confusing for me.

Thanks!

Answer 1

I can only reply to 1)

rvec and tvec describe the camera pose expressed in your calibration pattern's coordinate system. For each calibration pose you get an individual rvec and tvec. Undistortion does not influence the camera position. Pixel positions are modified by using the radial and tangential distortion parameters (distCoeffs) resulting from the camera calibration.