i lost track sometimes when i move the QR marker, any thing i can do about it? i can sacrifice some accuracy if needed

[wanghetongtt]

[fspindle]

One possible reason is that the pixel displacement in 2 successive images is larger than the range of the tracker (http://visp-doc.inria.fr/doxygen/visp-daily/tutorial-tracking-mb.html#mb_settings). Evaluate you displacement and set the range accordingly (ie if displacement = 20 pixels, set range to 25)