This is amazing. EA1FUO has built nec2c into WebAssembly, and now you can do antenna simulations on your phone or desktop without depending on nec2c running on a server. You can also deploy it locally, and he provides instructions for how to do this on docker or bare, and you can run nec2c on the server if you like.
Takes seconds to simulate my inverted V, and it even displays updates on what it is doing while running the simulation. It then gives a 3d rendering that you can drag around to get a better intuition. As you hover your mouse over the model, it shows gain in dBi with elevation and azimuth.
Beautiful work!
I don't know where else he's active, but he's been posting about this on Reddit as he's been developing it:
https://www.reddit.com/r/amateurradio/comments/1rfsr6f/my_new_modern_free_and_open_source_antenna/
Source code GPLv3: https://github.com/EA1FUO/AntennaSim