3MF format import export support

[caniko]

https://github.com/3MFConsortium/spec_core/blob/master/3MF%20Core%20Specification.md

[ok1ok1]

3mf is quickly becoming the preferred format for 3D printed models. I hope support is added soon.

[xtemp09]

AMF support also would be good.

[donjan]

Real world user feedback: I enjoyed using MeshLab for quickly checking on models due to it's super fast startup, snappiness and good UX. But in the last few months I've been exporting all my models to 3MF instead of STL, and I'm receiving mainly 3MF, so it's dropped out of my use.

[thekorsen]

Just ran into the lack of 3mf support as a pain point. Its my preferred format due to the smaller file size for high resolution complex models, and the lack of support for it will make me look to other mesh decimating software tools.