How to do a manual calculation of worldpoints from image points with Matlab Computer Vision data

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HT 2017-2-10

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https://ww2.mathworks.cn/matlabcentral/answers/324361-how-to-do-a-manual-calculation-of-worldpoints-from-image-points-with-matlab-computer-vision-data

评论： Mingming Zhao 2017-10-21

I am Trying to get a grasp on computer vision. So far I have managed to calibrate a singel camera using Matlab Camera Calibrator, and done a planar object measurement that was incredibly accurate using an adapted example given on this site. Matlab calculates worldpoints automatically, but I want to learn how to do It manually using intrinsics and extrinsics. Can anyone here help explain to me how to do It? I feel I am pretty close to accomplishing my goal, but I am stuck at the moment.

From Matlabs Camera Calibrator I get these intrinsic og extrinsic parameters

intrisic matrix = [3344.2 0 0 ; -0.6732 3330.6 0 ; 2141.6 1475 1];

rotational matrix = [0.9996 0.0267 -0.00058362 ; -0.0267 0.9996 -0.0049 ; 0.00045327 0.0049 1]

translational vector = [-180.3688 57.61 1427.3 ]'

Using the cameraParams, rotational matrix and translation vector i get the results I want with the pointsToWorld function, but when trying to calculate this manually I don't. I have tried setting up the full camera matrix and multiply this with the worldpoints to get image points, and the invers.

given the Image points [1582 957] the pointsToWorld functions give me these worldpoints [-66.1856 -278.1794]

I would really appreciate It If someone could please spare some time to explain this to me