Variations fonts and OpenType 1.8

There's not really a connection. Metafont supported variate-able parameters, but as the variables in a parametric equation. The differences between Metafont and outline fonts are too great in other respects.

Font designers have been interested in variations for quite a long time; they have simply distributed them as sets of individual font files. In recent years a lot of work has been done on the font-editor side of things to make creating interpolatable masters easier and to make generating instances from those masters more reliable, too. In a sense, the variations-font work is a straight extension of that trend, moving it from a build-time process to a run-time process.

Nate

The main problems with METAFONT are that (a) it was ahead of its time by 50 years or so, and (b) type designers have apparently not bought in any great way into the idea of designing fonts by coming up with equations for the computer to solve rather than drawing stuff – something which a genius-level computer scientist like Donald E. Knuth would take in his stride but there aren't too many of those around who are also into typeface design. METAFONT gives us a great way of generating font variations by twiddling mathematical parameters that are built into the font design, but the problem is to come up with font designs that incorporate the right parameters to twiddle such that twiddling them leads to useful results. Knuth's Computer Modern fonts are quite interesting in that respect, and there have been a few more experiments in that area, but for the most part the idea hasn't caught on.

In practical terms, the difference between METAFONT and the type rendering systems we use today is that METAFONT is based on “pens” on the design side and pixels on the output side (a consequence of Knuth's mathematical acumen and early-1980s technology, respectively) , while today's systems are based on scalable outlines at both ends. In effect, METAFONT produces pixel-based representations of glyphs at “compile time” while OpenType and friends do it at “run time” (i.e., when stuff is being displayed). This has various ramifications for things that are reasonable to do with either systems such that we end up with basically different worlds.