Modifying open source font – Advice needed on whether to use OTF or TTF

1

I am designing a custom version of Inter Semi Bold Display, an open-source font.
I would really appreciate some advice on how to do this best— I understand there is source code but I have no idea how to use it, and I can’t see any way to get a master glyphs file.

So my question is, which export of the font would be best to re-open in glyphs, to then re-export with my modifications — would it be OTF or TTF?

Are the vectors the same in both OTF and TTF? Would the export settings in OTF be more compatible than in TTF?

Any advice would be greatly appreciated.

2

The sources are here: inter/src at master · rsms/inter · GitHub

3

Appreciate your response George.
I have seen this but can’t work out how to download the package as a glyphs file to work locally on my computer… is this possible? I don’t know how to use the source code / Python etc…

4
  1. Go here: https://github.com/rsms/inter/tree/master
  2. Click on the green Code button and then Download ZIP.
  3. Unpack the Zip file and go into the “src” folder.
  4. Open either of the two “.glyphspackage” files with Glyphs.
5

Wow! Thank you so much Florian.
This works.
The masters are set to Thin/Regular/Black and the display variant, as expected.
Could you please advise best practice to add Semi-Bold Display to these masters so I can edit this weight?
Thanks a lot!

6

Select the instance in the Exports tab. Click on the + icon in the bottom left and select Instance as Master.

7

Usually you do not edit each style individually. I would edit the neighboring masters to get the instance as you like it.