The two of you who have downloaded my RoundEdge module from the Object
Collection may have noticed a gap in the sample images.  This gap was for an
oblong toroid.  However, to fit the theme of the module, the toroid would have
to be able to serve as a rounded edge or join for scaled cylinders.  To do
this, the central curve, the extreme inner curve, and the extreme outer curve
of the toroid must all be ellipses.  A sphere sweep does not satisfy this
condition (except for the boundary case of the circular torus).

So towards the end of August, I drew a diagram of an elliptical torus, and
stared at it.  A pattern emerged almost immediately, but it just sat there
looking pretty.  Hrummph.  I continued to stare at the diagram.

Finally, a couple of weeks ago, the pattern whispered to me from the graph
paper:

   "t^4 - 2*z*t^3 + (x^2+z^2-d^2)*t^2 + 2*d^2*z*t - d^2*z^2 = 0
   Solve for t."

:-O

No, no, no, it can't be!  Let me recheck my derivation.  It checked out.  But
I'm prone to mixing up signs, dropping coefficients, and getting exponents
wrong, so let me plug this into a spreadsheet just to make sure.  The
spreadsheet responded, "Your numbers are perfect.  Good luck with that formula.
 Bwa ha ha ha!"

So here I am, having to (re?)learn how to solve a quartic equation, and a
messier one than you'll find on any algebra exam.  I entered the "depressed
quartic" stage into the spreadsheet, and it checks out.  But after that, I'm
flying blind until I drag a "solution" out kicking and screaming.  I look
forward to rendering the result.  I *hope* it will be an elliptical torus.

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