Best camera setup and possibility of having the third camera behind the subject

[Mahsa Agz]

Dear OpenCap Team,

I hope this message finds you well. I am interested in understanding the optimal setup for using two or three cameras with your system. Specifically, I would like to know the recommended distances and angles for positioning these cameras. Additionally, I am considering a setup where one camera is positioned behind the subject, as shown in an attached image. Could you please advise on the appropriate placement of the calibration checkerboard for this arrangement, and guide how to properly calibrate the system in such a configuration?

2cam-setup.png (34.43 KiB) Viewed 529 times

3cam-setup.png (40.36 KiB) Viewed 529 times

Thanks.

[Scott Uhlrich]

All cameras need to be able to see the checkerboard, so you cannot have one behind the subject in this case.

The optimal setup very much depends on the activities you care about and your desired capture volume. Every body part needs to be visible to at least 2 cameras at all times, so if you have occlusion issues, it is helpful to add cameras. For walking, squatting, jumping, 2 cameras is fine. For an activity with the leg occluded in the back (e.g., a Y-balance test, 3 cameras is better). The height of the cameras can also affect occlusion, so having the cameras low to the groundcan often help.