Why are inflections on curves bad? I remember learning not to have inflections back when I was learning to draw type, and both Fontlab’s FontAudit and Jens Kutilek’s Red Arrows highlight them as a problem. But I’ve designed a typeface with inflections all over the place and they don’t cause any problems that I can spot.
3
Comments
[Probably a topic for another thread: I've had some interesting experiences making variable font outlines with ink traps. Because inter-axis interpolation in OTVar is additive, it is quite easy to have ink traps in unmastered corners of the design space behave in weird ways, e.g. pushing out below the bottom of V in heavy/small mixes.]
For instance, here is a foot serif from Adobe Garamond (1997).
FontLab’s FontAudit only warns about inflections that are close to the start or end of the segment, because those are probably unintended.
Glyphs will add explicit inflection points automatically when exporting to TrueType. If you convert manually (Paths > Other > Convert to Quadratic), inflection points are not added and your curves may be seriously messed up:
You can fix that by adding offcurve points to the problematic segments (so there is the same number on each side of the inflection) and refitting the curves to the original PostScript curve:
This way the inflection points can stay implicit and will not cause kinks in the interpolation.
We did a lot of work like this recently as shown by Luc(as) in this video from TypoLabs starting at 13:13 minutes.
Has someone run into such trouble? It was a long time ago I worked on such 3D letters.
Glyphs is doing that automatically for some time, otherwise the TT conversation would not work. It will insert points in corresponding segments even if the other masters do not have an inflection.
> If you convert manually (Paths > Other > Convert to Quadratic), inflection points are not added and your curves may be seriously messed up:
Nobody told me. I’ll fix this.
> I'd rather get a warning (too) since in tight quarters it can mess up.
I would like to see an example. Converting outlines can go wrong always, inflections or not.
Another unfortunate outline brittleness is what I call "half-dead" curves: where one end doesn't have a BCP. I find them highly elegant in terms of designing* (especially when adding traps) but there's some badly assumptive software out there that breaks it.
* Like when I'm watering my yard I don't want to have to also be at the other end telling the water how to land.
http://typedrawers.com/discussion/comment/35580/#Comment_35580
If the online service claims to offer support, it should be able to handle such curves. Or you run a filter on export that inserts the inflection points on export.
Also, is there are difference between inner and outer anchors? Can I get away with leaving the, say, leftmost inner contour of an O without a cardinal anchor? (These are the anschors that are at the very top (North), bottom (South), East etc.)
The original Adobe Type 1 font specification has an example almost exactly like yours, except with the fill reversed, and rotated 90 degrees. They specifically suggest leaving the point off in their example.