Font type = variable: Massive interpolation bugs

Hello, I noticed a rather serious issue when working with the font type = variable interpolation method in 3.2.

I have a font with quite a few intermediate layers for numerous glyphs. I have the intermediate layers set up so that they form a rectangular design space, otherwise I was experiencing growing and shrinking glyphs in the variable font. So I fixed that (by adding the same intermediate layers on the italic axis as on the roman axis, for example) and it works well.

Exporting the variable font works fine, no issues. Exporting the static fonts is a different story, however. I have the font type set to variable (in Font Info > Other > Font Type). Using this setting yields (I think?) the same kind of growing/shrinking glyphs for the static exports as I previously was experiencing, despite the variable font working fine:

Setting the font type to Default again works.

Can you send me the file?

Here’s an example:

Interpolation_Error.glyphs (7.2 KB)

I made two masters and added one intermediate layer, simply interpolated directly between the two masters.

If I set the Font type to Variable, the instance preview (and the export) looks like this:

I found this also affects metrics references in intermediate layers. Meaning if I have an intermediate layer and use a metrics key that references a glyph which morphs like in the screenshot, those faulty metrics will be applied to the intermediate layer. Again, this only happens if I set the Font type to Variable.

I’ll have a look.

I am having similar problem. The instances are not displayed correctly in Preview area as well. @GeorgSeifert what is the difference between ‘default’ and ‘variable’ in Font Type? What is the benefit of setting to ‘variable’?

Setting the font type to Variable means that you get the exact same interpolation for instances as for variable fonts. There are (theoretically) no discrepancies between your variable font instances and static instances.