Interpolating Glyphs with Different Path Counts

Hi,

I recently came across this project and found it very interesting: https://timesnewarial.liebermannkiepereddemann.de/

I have experience creating multiple masters and building a variable font. However, I’m wondering about one scenario: if the glyph outlines of the fonts differ in their number of paths, isn’t interpolation impossible? Does that mean you have to manually add matching numbers of path points so that they can be interpolated? Is there any way to automate this process? I can imagine that mixing a serif and a sans would be inherently difficult, but with similar typefaces you could probably calculate the intermediate spaces mathematically and automatically insert the missing paths. A similar principle exists in SVG morphing? Is there a function or plugin for this? Could you even train a GPT model to optimize the output? If it’s tricky in Glyphs, is there a way to do something like this in RoboFont or another application?

Any help would be greatly appreciated.

Best,
Alena

I think it’s manual work. You can extract the font from the website and import it into Glyphs to inspect it. In the Arial source, the points needed to form the serifs are all there in logical locations:

They had to invent a new g (middle) for Arial to be able to interpolate: