# A Fully-Automatic Gap Filling Approach for Motion Capture Trajectories
## 7 Conclusions  
In this work, we proposed a fully automatic approach to the gap filling problem. The method was framed as an optimization problem that has simultaneously explored the restrictions between markers' distance and their movement dynamics in a set of empirical principles and equations. We tested our approach in a set of artificially generated gaps using the full body marker set and compared the results with three other methods available in commercial software, achieving better performance in all tested conditions. The optimization approach ensured that the best solution could be found using the information available at each instant--without any restriction concerning length and number of missing markers or movement complexity. The method was designed to fully automate the task of the gap filling by assuming the prior labelling of the markers as part of the post-processing of MoCap sequences in motion analysis. The method finds applications in health or sports-related areas, requiring no pre-recorded data, no prior knowledge about skeleton constraints and rigid bodies and no manual intervention. The automation of this process avoids manual operation required in most commercial systems to perform the task of gap filling, reducing the number of man hours and the overall costs of the task. In the future, we should test our algorithm in different marker sets and different movements, providing a more general understanding of its performance in different conditions. Hyperparameters defined empirically in this study--e.g., the thresholds used to identify auxiliary markers--should be further investigated and fine tuned considering their impact on the overall performance of the method when applied to the different conditions. Moreover, we should aim to test our approach in real scenarios, i.e., gaps occurring naturally when a MoCap sequence is collected. Since our approach requires no manual intervention, the time required to reconstruct trajectories is only computational--for gains in efficiency, the multiple initialization feature can be employed. Processing time should be thoroughly investigated and possibly improved in a future study. Real-time capabilities and performance under real-time requirements should also be investigated in order to support applications in computer animation-related areas. **Author Contributions:** Conceptualization, [PERSON], V.G. and J.S. ; methodology, [PERSON], V.G. and J.S. ; software, [PERSON]; validation, [PERSON], V.G. and J.S. ; formal analysis, V.G. and J.S. ; investigation, [PERSON], V.G. and J.S. ; resources, [PERSON]; writing--original draft preparation, [PERSON], V.G. and J.S. ; writing--review and editing, [PERSON], V.G. and J.S. ; visualization, [PERSON] and [PERSON]; project administration, [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript. This work was performed in the context of the project VITAAL (AAL-2017-066), funded under the AAL JP and co-funded by the European Commission and the National Funding Authorities of Portugal, Belgium and Switzerland, and in the context of the project IANVS (AAL-2018-5-116), funded under the AAL JP and co-funded by the European Commission and the National Funding Authorities of Portugal, Belgium and Switzerland. Ethical review and approval were waived for this study since all data used in the experiments corresponded to publicly available datasets that were not collected by the authors. Not applicable since all data used in the experiments corresponded to publicly available datasets that were not collected by the authors. Data used in this project were obtained from CMU's motion capture database (mocap.cs.cmu.edu), which was created with funding from NSF EIA-0196217. Data were also obtained from the motion capture database HDM05. The authors would like to acknowledge all authors of the public datasets used to conduct the experiments. The authors would also like to thank [PERSON] for the design of the three principles' images that illustrate the proposed method.