It provides an interactive 3D view of the first ten equipotential
shells for the 1/r potential. One octant has been cut away so
that you can see inside.
I consider the 3D perspective to be useful. It provides a good
picture of what the potential is doing. I consider the applet
to be useful, because drawing such things by hand is a nightmare.
Also, interaction makes the view even more informative.
I did this by modifying some existing code ... some code that
I didn't write and don't even understand very well. I thought
this would be hard -- i.e. it would require understanding the
code -- but I got lucky. I just kludged a few lines and voilà!
It would be nice to have a toolkit for doing such things in
a non-kludgey way. Maybe someday.....
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While we are on the subject: Writing in javascript is infuriating.
It reminds me of writing in assembly language. I've done my fair
share of that, and I don't want to do any more. It's not a good
use of my time.
I would rather have an industrial-strength programming environment.
Something like C++. I reckon C++ is to javascript as chain-saw
is to butter-knife.