I was contemplating this years ago, but I never got around to it till now.

Using nothing but this illustration

http://kja-illustrators.com/open.asp?port=341&n=Total-Solar-Eclipse-Geometry%203D%20illustration&p=23140

and basic math (point to point line, slope-intercept line, algebra, and trig) I figured how to calculate the 3D umbra cone. The only data I used is the Simon1994PlanetaryPositions built into Cesium itself, and Sun/Moon radius.

Pleasantly surprised to find that the cone to globe intercepts matched that found here

http://eclipsetracks.org/#2020-12-14

The 3D umbra cone is educational. It does not reach that far, and a combination of factors have to line up:

-The closer the Earth is to the Moon the better (deeper into the cone the Earth is.)

-The further the Moon is from the Sun the better (the more elongated the cone becomes.)

Going to test a couple more total eclipse dates, then finish up making a penumbra cone.

Just added 2021 Dec 04 total eclipse

It also matches up with http://eclipsetracks.org/#2021-12-04

I must say I’m very impressed by Cesium’s built-in astronomical data and shapes!

Here’s the eclipse list I’m using to find total eclipses

en.wikipedia.org/wiki/List_of_solar_eclipses_in_the_21st_century

OK, this is the last total eclipse 3D umbra video before I add the penumbra cone. This one zips right down the middle of North America, and appears to be a good sized intersection.

As usual it matches up with http://eclipsetracks.org/#2024-04-08