Glyphs trying to force inetrpolation between normal and bracketed masters

Hi there,

My normal masters are compatible between them and my bracketed masters are also compatible, but current (latest 2.5.2) is trying to force compatibility between normal and bracketed masters.

I generated a font and the glyphs from the bracket trick are interpolated but not the normal ones, although the 3 masters are compatible.

Any idea on how to solve this?

The screenshot shows two separate Interpolations. Which one of these are the bracketed layers, and which ones are the default layers?

The program should be interpolating from the masters (left to right) 1, 4, 5.
2 and 3 are bracketed masters.

This can happen when you have a breakpoint ad the same place where you have an instance. And can you show a screenshot of the layer panel?

I have no instance at 140. Funny thing is I have a regular MM file with exactly the same settings and it’s working well.
I can’t find what is wrong with this glyphs. I just sent both files to

The extra bold is interpolating from the two light masters (that is a particularity of the algorithm). You can avoid this by adding a Disable Masters=Book custom parameter in the instance.

I don’t get it. Why it’s not doing there is no problem in the regular files? The setting are the same.
The problem are the bracketed masters getting in the way.

The boldest instance in the Regular is not extrapolating.

If I remove the extrapolating instance, I still have interpolation problems in the Italic masters.
And if I set all italic Instances on exactly the same as in the regular masters, the problem persist.

You might need to save and re-open the file. Sometimes, the master compatibly is not proper updated.

OK, now it works after restarting. So the rule is… When extrapolating in a 3 masters scheme, the third, non relevant master should be disabled? Isn’t it a bit messy? Shouldn’t it be fixed in Glyphs and not by means of a hack?

I’ll try to get this fixed. The interpolation part is very complex and a change like this might have consequences elsewhere.