Maxwell's equations on a 3D Yee grid, leading with energy conservation and far-field decay.
See it run - a worked example, 100% in this browser tab
The problem
Spinning up Meep or Lumerical for a quick electromagnetic sanity check is heavy when you only want to confirm energy conservation or far-field decay.
The local-first solution
This plugin drives the real wasm FDTD engine in the browser to leapfrog Maxwell's equations on a 3D Yee staggered grid, leading with two validated facts: source-free energy conservation and dipole far-field 1/r decay.
What it does
Leapfrog FDTD update on a 3D Yee staggered electric/magnetic grid
Source-free energy conservation as the bounded-energy diagnostic
Far-field 1/r envelope decay check with a dipole source
Engine's own GeoNum trust verdict passed through unchanged
Honest scope
The default has pml_thickness = 0, so the domain is a periodic 3-torus (fields exiting one face re-enter the opposite face) - the right setup for the two validated facts but NOT an open-region antenna or photonics solver. A bridge to HPC, not a replacement for Meep or Lumerical, and EXACT is never asserted for a discretized leapfrog field.
Authorities cited
Yee, K. S. (1966). Numerical solution of initial boundary value problems involving Maxwell's equations in isotropic media. IEEE Trans. Antennas Propag. 14, 302-307. DOI 10.1109/TAP.1966.1138693.
Taflove, A. & Hagness, S. C. (2005). Computational Electrodynamics: The Finite-Difference Time-Domain Method, 3rd ed. Artech House. (3D Yee Courant stability c*dt <= dx / sqrt(3).)
Run a Yee-grid FDTD check
Run the solver in the browser and save the result to Sandbox, attach it to a Worklog case, or route it into a Gate client portal. Nothing is uploaded to anyone's cloud.