3MF support for Mittsu.

Just install:

bundle add mittsu-3mf

Then require in your code:

require 'mittsu/3mf'

Currently this gem just includes an exporter. Loading 3MF files is "coming soon".

exporter = Mittsu::ThreeMFExporter.new exporter.export(object, "output.3mf") 

This code was originally written for Manyfold, supported by funding from NLNet and NGI Zero.