A question was asked recently on another forum that made me rethink my understanding of vector formats. TrueType fonts are in a vector format and - I had previously thought - that if a vector editor was to present them for editing, it would present only the points described in the original font shape and, if there are curves, present appropriate handles at only those points.
I don't see how one software package (Glyphs) can interpret a in Arial as 20 points and another (Illustrator) interpret it as 37 points when converted to outlines or expanded. I don't have Glyphs to hand but can confirm that Illustrator did present 37 points when trying myself. The original poster provided illustrations of both outcomes as follows:
The a from Arial in Glyphs:
The word arial in the same font in Illustrator (focus on the points in the letter a vs the same in Glyphs):
I understand the basic concept of vector image files; that the data is a series of coordinates for points and other information mathematically detailing the amount of curve (or lack of) between points. What I don't understand is two things:
Is the data in a TrueType font not described in such a way that it can be very literally translated into an editable shape in Illustrator when outlined? Why has Illustrator added additional points? Or is the TrueType format not described using points at all (I don't see how)?
Glyphs appears to demonstrate that it's possible to describe certain curves in a limited amount of points. Why would a highly reputed piece of software like Illustrator need more points to describe the same curve? I would see this as a poor translation and I imagine most users would expect this too. This overlaps with question one a little so perhaps a single answer covers both.