Checkerboard Error

[Hoon mini]

Hi
I needed a larger checkerboard than the one provided by OpenCap, so I created a B4-sized checkerboard on the calib.io website (checkerboard: 8x11, checker size: 28mm). During the calibration process, the camera continuously fails to recognize the checkerboard. How can I resolve this error?

[Matt Petrucci]

Hi Hoon,

You should be able to use your custom checkerboard, you just have to make sure that your row and column numbers are correct. Note, if it is 8x11, you should input 7x10 into the web app (see this video https://www.youtube.com/watch?v=T6TkFLEfQ0Y&t=67s) as it is only counting the internal corners. Also ensure you are changing the checker size to 28 mm.

If that isn't your problem, also make sure that all cameras can see the checkerboard clearly and the angle between the checkerboard and any of the cameras is not too steep (i.e., the angle between the plane parallel to the board and your camera is not too small).

Matt

[Hoon mini]

Thank you for your response. I want to proceed with an OpenCap validation experiment, but I'm wondering how to align the global frame of the motion capture system with the frame of OpenCap???

[Antoine Falisse]

I believe we answered you in a separate post.

[Matt Petrucci]

Hi Hoon, the picture in the readme for this code should also help: https://github.com/stanfordnmbl/opencap ... ntegration. You would just apply the rotation and translation between the two coordinate frames.