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Multiple markers along trajectory

asked 2018-10-11 04:48:14 -0600

klayman gravatar image

I have multiple planar markers in the scene. At any time I see one or two, sometimes three markers. I want to track camera pose on a trajectory which pans and rolls.

Right now I can track the pose with solvepnp for one marker at a time. I need to somehow "stitch" together the tracked poses for the other markers. For example, by calculating the "relative pose" on those frames where multiple markers are visible at the same time.

Do you have suggestions? Is this already supported by openCV? How can I build a smooth stitching?

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answered 2018-10-12 21:19:13 -0600

Tetragramm gravatar image

It's on my list for the mapping3d module I'm working on, but not done yet.

Basically, you have to take one as your primary, then when you have another in frame with it, reverse the R|t to it, and combine that with the R|t to the first marker to get the location of the second in relation to the first. Then any future calculations with only marker 2 include the R|t to the location of the second marker.

It's best to average the result over all the frames that contain both to try and get rid of bias and noise.

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Thanks, that's the solution I'm trying right now. Brings about a few questions on how to average transforms and what to do during the transitions as I clearly want to have the average transform at the end, but also a smooth join. Maybe a more global approach would be a better fit?

klayman gravatar imageklayman ( 2018-10-13 00:52:09 -0600 )edit

You can (more or less) average rotations using quaternions. Look it up to see what the limits are.

For a transition, you can take a couple of frames and average the old, so it smooths over, or use a kalman filter to estimate the values, or several other choices.

Tetragramm gravatar imageTetragramm ( 2018-10-13 21:46:26 -0600 )edit

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Asked: 2018-10-11 04:48:14 -0600

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Last updated: Oct 12 '18