I am working on a font experimenting with higher order interpolation (HOI) techniques by using virtual masters. There are three axes that must move in sync for this to work and I intend these to be used in conjunction with other axes; the preview panel in Glyphs App displays all these variations perfectly (slant axis at the max value, and incremental increases to the 3 italic axes):
On export however the interpolation does not work as previewed and is quite broken (the expected output was the rightmost /n in the above image):
I am unsure if the issue is with the way that Glyphs App is generating and structuring the gvar deltas, or if its interpolation engine is different than those of web browser and FontView
That is most likely because my code that computes the deltas for the intermediate masters doesn’t handle more than three axes very well. I’ll have a look.
I can confirm it is the way the deltas are being computed. I made a modified file for testing (all would-be virtual masters just as regular masters) and fontmake generates it properly.
