Meeting Abstract
Commercial 3D motion-tracking systems are readily available, albeit expensive, options for motion research in comparative biology. Most applications using these devices are in whole-body or whole-limb model systems. The extent to which smaller-scale, finer movements can be captured precisely with such systems is limited by factors such as marker size, and the ability of markers to non-invasively track movements without impediment. Motion capture markers in commercial systems range from 3 to 25 mm in diameter, many of which may be inadequately sensitive to smaller-scale movements that occur in motions such as chewing. We designed and tested a cost-effective alternative to commercial turn-key systems for capturing jaw motion in mammals. Using a VROMM (Video Reconstruction of Moving Morphology) based approach, we analyzed the precision and accuracy of a motion capture system based on videos of 3 mm diameter fluorescent paper markers, recorded by two synchronized cameras coupled with blue light filters and blue LED light source to enhance marker-to-background contrast. Using free software (XMALab and R) and custom scripts, our protocol achieved a mean reprojection error of 0.23 pixels. This value translates to a mean accuracy level of 0.04 mm, more than twice as accurate as those reported for several mainstream commercial systems (0.10 to 0.30 mm). For angular measurements, our protocol achieved an accuracy of <1 to 2 degrees. These experimental results suggest that this relatively simple and cost-effective protocol has comparable or lower levels of measurement error compared to commercial systems, and could be suitable for kinematic studies of finer-scale movements in model systems with small ranges of motion. The non-invasive nature of the protocol makes it a viable alternative to expensive commercial systems for deployment in field or lab settings.
