TREWARTHA, G., YEADON, M.R. and KNIGHT, J.P. 2003. Colour based rigid body tracking using three-dimensional graphics models. Sports Engineering, 6 (3), pp.139-148.
This paper introduces the first stage of a new model-based approach to three-dimensional (3D)
human movement tracking. A ‘generate-and-test’ matching procedure was adopted by matching
rendered images of a 3D computer graphics model of the human body to target images of rigid
body motion. The set of pixels to be compared were just those corresponding to the model of the
body in the rendered images. The matching criterion to optimise model position and orientation
was based on the minimisation of the RGB colour difference between generated model images and
associated target images. The method was able to track synthetic image sequences of a half
twisting somersault accurately with root mean square errors of less than 5 mm and 0.3° for
position and orientation estimates respectively. The suitability of the proposed approach for rigid
body motion tracking was supported by additional tracking experiments on video image sequences
of ‘wooden cross’ trajectories. Comparisons of tracked estimates against manual digitising
estimates returned relatively small rms difference values on both side somersault and twisting
somersault movements. The proposed approach has the potential to track video images of a
human torso using a rigid body model and hence to track articulated movements by successively
adding segments to the model in a hierarchical manner.