@letterror @klim @RoboFont @drawBot The biggest issue I find in variable font development—beyond more than one axis—is that one can’t know at the outset how many masters one is going to need, and how much work is going to be involved in making corner locations correct* until one has completed and tested the axis extrema masters.

This obviously has implications for pricing variable font making.

*Where ‘correct’ is a locally and technologically restricted ersatz for perfection.

@klim @letterror @RoboFont @drawBot MM development always involved a predictable number of master designs derived from the number of axes.

I made this 2016 illustration of a three-axis variable design space using an MM font (Kepler), because I didn’t have an actual OT variable font. In the MM font, every one of these letters represents a complete master. In OT var, all the orange ones are technically optional, but you can’t know which ones you’ll need until you’ve made the green ones.

@klim @letterror @RoboFont @drawBot OTvar is defined in terms of a single outline set (which may or may not correspond to a design master), and deltas to other fixed locations in the design space. The only locations that technically need delta sets are the extrema of the individual axes, and those tend to be design masters in sources.

The interaction between the axes is indeed extrapolated—but extrapolated within the confines of the axis extrema—unless additional delta sets are introduced.