Sorry for not getting back in here sooner, had a bunch of other projects on… So, the bad news is that although I finished the latest revision of my script and it does what it is supposed to do, in testing on letterforms with fillets, in the end it only helps a little… So it’s not going to be extremely useful, I’m afraid. I’ll try to explain:
There are two things that cause fillets to go nutz. One is that Rhino can’t figure how to extend/trim adjacent fillet sections to mate with each other. This often happens where there is a very slight kink in the edge/surfaces being filleted, or when they make an extremely sharp angle (angles in between those two generally work). So they end up being untrimmed at the joint and then the fillet fails to trim the base object. The script tries to fix those situations.
The other problem is when you try to wrap fillets around corners that are too tight for the fillet to fit (i.e. smaller than the fillet radius. The script does not address this situation, and as letterforms have many such tight curves, even if all the edges have good structure with no kinks, the fillets will often fail anyway. In order to make it work, you would have to remodel each letter to have no radii smaller than your future fillets.
To answer questions:
Yes. This will identify some potential trouble spots at least, especially if you see the graph “go crazy” as some points. But it will not necessarily guarantee successful filleting afterwards.
It’s a nautical term as far as I know, used to indicate the smoothness of the curves/surfaces used to design hulls. Smoother surfaces result in better hydrodynamics.
fair curves [¦fer ′kərvz] (naval architecture)
Curves which are smooth without sharp changes in direction over any portion of their length.
Well you can dive into McNeel’s explanation of NURBS geometry, it is a bit geeky/techy, but
maybe it will help. You don’t really need to be an expert on this stuff to use Rhino, of course, sometimes it just helps explain why things work like they do.
For the Illustrator-Rhino thing, Illustrator uses Bézier splines - a predecessor and subset of NURBS, the mathematics of which was pioneered by Pierre Bézier and Paul de Casteljau, both French automotive/aeronautical engineers.
The Bézier splines used in Illustrator (and also many type fonts) are all single span degree 3 curves with 4 control points. For complex curves, they are hooked together end to end, but the tangency at the joints is not guaranteed. Depending on how they were drawn in Illustrator and also I guess how they are translated into NURBS by Rhino, they can have a LOT of points, lots more than are really needed to describe the curve within tolerance.
So it can make much cleaner geometry if you take time to fix/rebuild them, but this process is not an automatic one-click operation. It also takes some experience to know what methods of fixing might be best/fastest (if they need to be fixed at all) for your application. I would not want to trace over them though, I still think some more automatic methods like a judicious Rebuild of certain sections, using FitCrv and or Fair will go faster. I have a tendency to make a copy of the curves in a contrasting color and lock the originals, then start fixing the copies, making sure they don’t deviate too much from the originals.