A Guide to Inverse Kinematic Marker-Guided Rotoscoping Using IK Solvers

Synopsis X-ray Reconstruction of Moving Morphology (XROMM) permits researchers to see beneath the skin, usually to see musculoskeletal movements. These movements can be tracked and later used to provide information regarding the mechanics of movement. Here, we discuss IK marker-guided rotoscoping-a method that combines inverse kinematic solvers with that of traditional scientific rotoscoping methods to quickly and efficiently overlay 3D bone geometries with the X-ray shadows from XROMM data. We use a case study of three Nile crocodiles' (Crocodylus niloticus) forelimbs and hindlimbs to evaluate this method. Within these limbs, different marker configurations were used: some configurations had six markers, others had five markers, and all forelimb data only had three markers. To evaluate IK marker-guided rotoscoping, we systematically remove markers in the six-marker configuration and then test the magnitudes of deviation in translations and rotations of the rigged setup with fewer markers versus those of the six-marker configuration. We establish that IK marker-guided rotoscoping is a suitable method for salvaging data that may have too few markers.

Automated summary

Synopsis X-ray Reconstruction of Moving Morphology (XROMM) allows researchers to observe musculoskeletal movements. IK marker-guided rotoscoping is a method that combines inverse kinematic solvers with traditional scientific rotoscoping methods to overlay 3D bone geometries with X-ray shadows from XROMM data and salvage data with few markers.