OPynSim is a python-native API for musculoskeletal modeling that doesn't compromise on nearly 20 years of research, feature development, and UI development from Simbody, OpenSim, and OpenSim Creator.

• 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 both 2D widgets (plots, buttons, text) and real-time 3D rendering.
• High-performance native bindings, implemented with nanobind.
• Almost zero runtime dependencies. The entire OPynSim C++ stack is built into a single native extension module that only depends on common system libraries. The Python stack only depends on numpy (unpinned).
• Stable Python ABI implementation. Each release of OPynSim works on any Python version ≥ 3.12 on Windows, macOS, and major Linux distributions.
• Excellent compatibility with OpenSim. The OPynSim codebase uses a lightly-patched forks of opensim-core and simbody. The native part is already used in production releases of OpenSim Creator, which ships to thousands of OpenSim testers users.