Attached is version 8, the "final" version of SeiffertCurve script, which is FAST and doesn't seem to fail, provided
the values are kept less than a few hundred.

The "rate limiting" code of the curvefactory Update has the code inside of the .htm file, and the result is perhaps 10 times faster
than having all the code in the .js file.

I was unable to pass any parameter or arrays from .js to .htm file, without MoI having exceptions and being very slow.

So getting the endpoints and the unit sphere to Update was harder, but as those two are very short, and could be done fast as subroutine functions
in the .js file, that proved to be the way to do it. Having the end point showing allows the length of the curve to be adjusted, by trial and error.

The modulus k is locked to the range 0.1 to 10.0, or the negative. A negative modulus seems to be a mirror of the curve.
The Length factor, "numturns," is locked to positive, and greater than or equal to 0.1.
The number of points "per turn," is set to be at least 100.

For modulus of 1 or greater, the BoostC++ example was used to adjust the code so as to get a result that is a semi-spherical "hat."
(The prior code had an error, failure to swap cn and dn.)

If nothing else, it was good scripting practice.

- Brian