opynsim

[!CAUTION] This is currently PRE-ALPHA software. You can (of course) use it, but major architectural pieces are still being moved around.

OPynSim is a Python-native API for musculoskeletal modeling that doesn't compromise on nearly 20 years of research and feature development in the field.

• Documentation: https://docs.opynsim.eu
• Source code: https://github.com/opynsim/opynsim

OPynSim provides:

• A Python-native interface for building and manipulating musculoskeletal models.
• An integrated visualization API that supports real-time 3D rendering.
• High-performance bindings, implemented with nanobind.
• Almost zero runtime dependencies. It only depends on numpy ≥1.26.0.
• Stable Python ABI implementation. Works Python ≥3.12 on Windows, macOS, and Linux.
• Excellent compatibility with OpenSim. Can import/export .osim files and be used alongside the opensim Python API.

📖 Citing/Acknowledging

If you want to cite the OPynSim project, cite its proposal (we will publish something later on):

Kewley, A., & Seth, A. (2026). OPynSim: A python-native library for interoperable biomechanical simulations. Zenodo. https://doi.org/10.5281/zenodo.19493285.

Alternatively, if you want to make it clear that OPynSim is an active project, rather than a proposal, cite its NWO grant DOI: https://doi.org/10.61686/KYYRQ22856.

If you want to cite a specific version of OPynSim (e.g., for reproducibility, open science), then additionally cite the unique Zenodo DOI corresponding to that version, for example:

Adam Kewley. (2026). opynsim/opynsim: 0.0.7: Pre-Alpha Development Release (Version v0.0.7) [Computer software]. Zenodo. https://doi.org/10.5281/zenodo.21373996

❤️ Acknowledgements

We would like to thank Open Science NL (NWO), which currently funds OPynSim's development through its "Open Science Infrastructure" grant call (grant, announcement). You can read OPynSim's proposal on Zenodo.

We would also like to thank the Department of Biomechanical Engineering at TU Delft, which provides the institutional support necessary to keep OPynSim's development administered, supported, and stable.