Rotated splines almost ready.

I meant to have the next release done by now but I've gone down a few rabbit holes along the way.

The major enhancement I've been working on is the addition of optics objects that are defined by rotating a splined curve. This will allow all sorts of objects like parabolic reflectors, aspheric lenses, even fresnel lenses.

During developing this capability, I've also noticed - or maybe broken - the ability to combine object surfaces when those objects are really close together. This allows for doublets and other lens combinations where there is effectively no air interface between them.

Anyway, I'm almost there. I'm hoping to have the next release in a couple of weeks.

Cheers,

Kenneth.