Calibrating camera - ju1ce/April-Tag-VR-FullBody-Tracker GitHub Wiki

This will start the camera calibration sequence. Display the charuco_board.pdf on your monitor and enlarge it as much as you can. Turn off camera preview before starting. This must only be done the first time you use this program and if you change the camera you are using.

NOTE: The calibration board has to be completely flat during calibration, meaning that you can't display them on a curved monitor!

Quality of calibration will also depend on your camera settings! Make sure that the calibartion board will be seen clearly on the image, that it isnt too blurred. If it is, try to reduce the gain of camera. You also dont need to have exposure set as low as you will need for detection, you can set it higher if that produces a nicer picture.

A window will open with the camera feed. Every few seconds, the camera will take a picture. Move the camera around slowly, taking pictures of the charuco pattern from as many diffrent angles as possible. Diffrent cameras may require some diffrent strategies, but usually, if your camera has a high FOV, you want to take pictures from up close to the pattern (<0.5m), while on low FOV cameras you want to move further away (around 1m).

Since v0.4, the calibration will also give feedback on how good is the current calibration. The corners will stay on the image as dots, with the color representing their reprojection error: yellow is bad calibration, purple is good calibration. Make sure most of the dots are purple before proceeding to the next step! (or at least green).

Another indicator of how well calibrated is the camera is the grid: it has to be nicely spread over the whole image, shaking as little as possible. (On high FOV cameras, the grid can be a bit curved and smaller than the image. As long as the curvature is even and the grid is fairly still, it is fine). Once that is done, press OK to finish calibration.

Sometimes, if the picture is too blurry or the lightning is bad, the pattern wont be detected. Make sure you have uniform lighting.

Another thing to note is that the camera must not be mirrored! If the camera is mirrored, it will not detect the grid. You can fix this with the "mirror camera" parameter.

Examples of calibration:

Great calibration

Okay calibration

Bad calibration

Video example of calibration is avalible here

Another example is also shown in the video uploaded to reddit.

(Yes, its a download. Ill try to fix it so you can just watch it in the browser soon.)