OpenCap Calibration Origin

[Aaron Fox]

Hi OpenCap Team,

I have reviewed this and this forum post, and I can gather that the opencap origin/global coordinate relates to the position of the checkerboard origin. We are collecting opencap data concurrently with a motion capture system and I would like to be able to align the coordinate systems, but didn't collect any information on this during the opencap calibration. I had assumed that the OpenCap data might store some of this info, but now that I think about it I'm not sure how I'd align it back to the motion capture data even if it did. So first question, is there any sort of origin/calibration info stored in the OpenCap data? And if not, the second question is that if we have collected the OpenCap static trial at the same time as our mocap static trial - do you think could we determine the coordinate system offset by comparing the pelvis translations between the opencap and mocap static motion?

Aaron

[Matt Petrucci]

Hi Aaron,

Did you happen to put the checkerboard in a consistent location in your mocap space? We have some code that enables you to align the origins if you can do a manual measurement. https://github.com/stanfordnmbl/opencap ... ntegration

Hope this helps,

[Aaron Fox]

Hi Matt,

Unfortunately no, I don't think we were that precise with how we placed each time - particularly as we were experimenting with camera positions and moving things a little around in the early stages. This is useful info for next time though.

As an FYI the calibration of sorts between the static trial seemed to work well, in that when posing the models from the static motion from OpenCap vs. the motion capture system they do end up well aligned.

Aaron

[Matt Petrucci]

Great! Thanks for sharing