How to make a variable font that goes from curves to straight lines?

I’m following this Glyphs tutorial in an effort to make a variable font that goes from serif to sans serif.

My intuition says I should take the serif curves and convert them into straight lines (by deleting the curve handles) and then move the anchors into place.

But I get these red lines when I toggle View > Show Master Compatibility, and the tutorial says (see under " 3. Compatibility view") this means:

it is a curve segment in one master and a line segment in the other, i.e., the segment types are not compatible.

My next instinct would be to make the handles zero length, but @GeorgSeifert says here

We strongly discourage the use of zero length handles.

So I am very unsure what to do! Can anyone suggest how best to handle this? See the attached image for a screenshot of what I have and the red errors.

I found what would seem to be a hack: I converted each straight line with a red error into a curve by holding down Option and clicking the line.

But I’m guessing there’s a much better and/or more proper way to do this?

This is the correct approach. From here, it’s up to you how you place your handles and nodes, as this will shape the interpolation results.


What about doing this with corner components? You’ll save yourself a lot of work.

Hint: for best interpolation results keep the relative distance between points (nodes and handles).

How are you imagining I’d use corner components here?

Definitely seems like a good idea if I’m going from sans serif to serif. Currently though, for better or worse, I’m starting from serif outlines and modifying them to be sans serif.

On interpolation, I’m actually not sure what it would mean to maintain relative distance between nodes/handles in this context. The sans serif version essentially collapses all the serifs down to nothing, so all points end up on a straight line. I am trying to keep the points the same on one (X or Y) axes relative to their original positions, which seems to help with interpolation. But do you have any advice on how I should be doing this for the best results?

You keep the ratios of distances between the points. Otherwise you risk a kink in interpolation. See the Multiple Master tutorials.

Yes. That will be good enough.

Cool, thanks. I did see keeping the ratio of distances in that tutorial. Just not sure how to go about that. Is there an easy was to see those ratios and rearrange points on the straight line to match them?

I imagine there’s a way to do it more manually by measuring the distance between each pair of points and the total distance and then calculating ratios and what the new distances (on the straight line) would be… but seems extremely tedious. (Also I don’t know how to see the distance between points along a curve — assuming there’s a way?)

Thanks for your feedback here and the super excellent documentation/tutorials. I’m brand new to Glyphs and super impressed and grateful!

Welcome to Glyphs; you will be glad you joined us.

Check out these three plugins; they may be of help to you.
Show Distance & Angle
Show Distance Between two Points
Show Smooth Node Angle and Proportion

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