Interpolation problems in SourceSerif4[opsz,wght].ttf

[behdad]

Hello!

This is an automatically-generated report about possible interpolation problems in SourceSerif4[opsz,wght].ttf, as found in the Google Fonts catalog.

To download a PDF version of this report with helpful visuals of the problems, click here; Or to view it on the GitHub website, click here.

The report follows:

Glyph uni20A6 was not compatible:
  Masters: '', 'opsz=8.0':
    Contour 0 structures differ: '', 'opsz=8.0'

This report was generated using the fonttools varLib.interpolatable tool. We understand that sometimes the tool generates false-positives. Particularly for more complicated font designs. If you did not find this report useful, please accept our apologies and ignore / close it.

To give feedback about this report, please file an issue or open a discussion at fonttools.

[behdad]

Sorry for the noise.

[frankrolf]

I was also tempted to close this at first, but I think it's worth a second look. The interpolation is fine, but you'll see that points are "wandering" (moving across a long distance).

I'll make an edit as soon as I find a moment.

[behdad]

Hi Frank. Do you find this useful? It's a kink detector.

SourceSerif4[opsz,wght].ttf.pdf

[frankrolf]

Hi Behdad, thank you for this. I am aware of those kinks, but I don’t think there’s a way around them (except HOI).
I have made my own kinking reporter in RoboFont, and I left those points in deliberately – otherwise, the style of the terminal would have been compromised.

It’s tempting to flag those kinks as an error since it’s technically possible – however I don’t think they are very relevant.
A typeface in which all outlines are completely smooth isn’t necessarily better than a design where kinks may occur – especially if we consider the intended application size.

With respect for this work, and without any judgment – flagging those could be interpreted as “missing the forest for the trees“. :-) Still, I think it’s useful for the designer to be informed of kinking, so they can make a decision whether they are avoidable.

[behdad]

Thanks Frank for the feedback. I was still tuning my tool. With current default settings it doesn't report those anymore. It does catch major kinks that the designers want to fix.