### How to derive camera position from solvePnP? Not a repeated question.

Hi, can someone help me?
From the post, "camera-position-in-world-coordinate-from-cvsolvepnp"@ ~~statckoverflow, ~~stackoverflow, it gave the answer of how to derive camera position in world coordinate from cv::solvePnP. However, I still can not get a correct solution from that page.
My experiment is facing a wall with a poster and move straight toward the poster step by step. Unfortunately, the trace of the sequence of camera's coordinates are not a straight line.
From my understanding, solvePnP() will return the rotation and translation of the object in camera coordinate system. Notice that, they are object's rotation and translation in camera coordinate system. So, the whole question become: **Give a poster's rotation and translation in camera coordinate system, how can we derive camera's position in poster's original world space**?
From my understand go 3D computer graphics, I am skeptical about the solution from above post. Can someone help me to solve the puzzle. Thanks,