Known model I/O limitations

[redstrate]

There's a few model I/O limitations:

• Shape key import/export is still WIP and will probably not work. This mostly means you need to be careful with anything has sleeves.
• Any LODs other than 0 are not tested and will probably not work
• Adding/removing vertices "works" but results may vary

[redstrate]

On the note of shape meshes, I had some WIP code sitting around for import/export which I now uploaded. Exporting does work, but importing doesn't (yet). It does clear existing shape meshes for now, so it stops it from bugging out in game.