Interpolation in FL5 adds unwanted tangents

I noticed all my glyphs in an interpolated weight look ike this:

What could be the reason, and do I have to remove all tangents manually?


  • I've never found a way to automate their removal. I examine every glyph of every interpolation and remove them manually. I probably spent a 3 or 4 hours last month removing those things from a large interpolated family. I asked about this a few years ago (I forget which forum) and nobody had a solution.

    It's odd how some times it doesn't occur. Sometimes exactly the same glyph will have those errors on different diagonal lines.

    Similarly, you should keep an eye out for any glyphs with identical components. For me that's usually %‰…“”„"«»÷. The identical components will get swapped, seemingly at random. It doesn't matter if the components are ordered correctly. You can even interpolate the same fonts multiple times and get different results...sometimes. Changing the order of the components makes no difference to the outcome. If you deliberately put them in the wrong order, the results are the same. Strangely, the problem occurs for all glyphs with identical components or none. It's never just one case...which is good because it makes the problem easier to spot.
  • Vasil StanevVasil Stanev Posts: 537
    edited January 2019
    Which way do you order the components? I copy-paste each shape in the same sucession and this seems to remove the problems, at least it did in Glyphs.
  • Is this using the blend font function or the multiple masters function? I only ever did it using multiple masters and never had a problem.
  • Unrelated  but what is FontAudit complaining about though? Does it want you to add a node there because bcps aren't a tangent?
  • Chris LozosChris Lozos Posts: 1,226
    Fontlab is like riding an unbridled horse. You can have an exhilarating ride but don't expect to control every move.
  • Is this using the blend font function or the multiple masters function? I only ever did it using multiple masters and never had a problem.
  • If I'm making something new I'll use multiple masters but often I need to interpolate older fonts. If I only need to interpolate a few glyphs, it takes less time to blend and clean up than to set up multiple masters. For example, if I need to add new some currency symbols to an existing typeface, I blend, clean up, blend, repeat.
  • What Mark said. If you aren't getting good results, use multiple masters instead of blend.
  • I always used Mask-to-Master and all the points remained exactly as I placed them.
  • Same here.

    "Blend" can work with otherwise less-compatible outlines, which is handy for some things—although often just to show/explain/educate, rather than for production work, in my usage.
  • If you are using "Blend" you need to get your start points and contour orders right to achieve the best results.

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