Developing a Pipeline to Convert Marker Less Motion Capture Data from Theia3D into Open Sim for Advanced Biomechanical Analysis

Marker less motion capture technologies, such as Theia3D, have become popular for biomechanical analysis by eliminating the need for physical markers, therefore improving the ease of data collection and post-processing. A major limitation to this technology is the lack of tools that integrate marker less motion capture output into more advanced biomechanical analysis software, such as Open Sim. The absence of a workflow between these software prevents researchers from performing advanced biomechanical analyses using Open Sim’s modelling capabilities Thus, the main objective of this research was to develop a pipeline to convert the output from Theia3D into a compatible format for analysis in Open Sim. A subroutine was developed in Python to convert the Theia3D outputs into a format suitable for Open Sim. The test data included marker less motion data from treadmill running collected in Theia3D by 8 Sony cameras. The output of this data was in an .mot file that was processed to develop a file compatible in Open Sim. This process involved 4 key steps: (a) extracting kinematic data from Theia3D, (b) restructuring matrices to match Open Sim’s input requirements, (c) generating plots to visualize the motion, and (d) producing a compatible file that allowed for model scaling in Open Sim. The tool was tested by processing the Theia3D dataset, and successfully converted the marker less motion capture data into an Open Sim-compatible format that allowed for analysis. This tool provides an advantage to biomechanical researchers by integrating marker less motion capture data into Open Sim, expanding its applications of motion analysis. Currently, this tool has only been tested on a limited dataset, and future work will focus on optimizing the conversion algorithm and expanding compatibility with different movement patterns to enhance the usability and reliability of marker less motion capture data in Open Sim.