openEMS is a free and open electromagnetic field solver using the FDTD method. Octave/Matlab and Python are available as easy and flexible scripting interfaces.

Website: https://openEMS.de
Documentation: https://docs.openEMS.de
Github: https://github.com/thliebig/openEMS-Project

• Fully 3D Cartesian and cylindrical coordinates graded mesh
• Multi-threading and SIMD (SSE) support for high speed FDTD
• Octave/Matlab and Python-Interface
• Dispersive material (Drude/Lorentz/Debye type)
• Field dumps in time and frequency domain as vtk or hdf5 file format
• Flexible post-processing routines in Octave/Matlab and Python
• and many more

https://docs.openems.de/en/latest/install/index.html

Pull requests are welcome. AGENTS.md has the working rules — build, submodule handling, documentation and commit conventions — and applies to human and AI-assisted contributions alike. Disclosure and sign-off requirements are in AI_POLICY.md. The simulation code lives in the submodules; each has its own AGENTS.md.