Track marker¶
In this tutorial we will show how n-fold-edge CLI can be used to track a marker with a webcam.
First a marker is needed. In this tutorial we will use a marker of order 6 and it can be downloaded here and printed (the last page).
If n-fold-edge is not already installed, see installation.
With n-fold-edge installed the CLI can be run with:
python -m track-markers
or if the installation have added n-fold-edge to the path it can be invoked simply with:
track-markers
From here on out we will assume n-fold-edge is in the path, but if that is not the case for you replace track-markers in the following with python -m track-markers.
To use our webcam for tracking we will give track-markers a 0 as the video input which will use the default webcam. If another webcam is desired try with 1 or more.
track-markers 0 --show --order 6 --kernel-size 21 --output tutorial-marker6.csv
Here we also supplied the marker order 6 and a kernel-size 21 to use. A Larger kernel-size can give better results depending on the marker size but will be slower. we also tell the program –show to open a window with the webcam view. Another option is to use the –output-video to save a video. Last we tell the program to save the marker location to a csv file named tutorial-marker6.csv
When the window opens and show the webcam feed, try and hold op the marker and move it around. If the marker is found it will mark it with a red circle and a blue line.
To stop the program press q, esc or ctrl-c.
Below is a sample of the csv file with marker locations:
Frame |
x |
y |
direction |
quality |
order |
|---|---|---|---|---|---|
… |
|||||
57 |
365.601563 |
326.584640 |
1.764990 |
0.050800 |
6 |
58 |
364.123639 |
322.378904 |
-0.319500 |
0.030503 |
6 |
59 |
360.234427 |
314.376741 |
-0.294536 |
0.026498 |
6 |
60 |
356.916695 |
309.157411 |
2.852505 |
0.051228 |
6 |
61 |
354.409452 |
306.397820 |
1.811190 |
0.073916 |
6 |
62 |
352.042820 |
304.675182 |
1.813869 |
0.060549 |
6 |
63 |
348.620657 |
302.509173 |
1.826995 |
0.040862 |
6 |
64 |
345.164850 |
300.102629 |
-1.296454 |
0.066076 |
6 |
65 |
342.505863 |
297.894744 |
-0.237597 |
0.040265 |
6 |
66 |
339.940118 |
295.467012 |
-0.214262 |
0.076283 |
6 |
… |