> So 3dm can save 2 different sorts of "curves" minimum (?)

Well, the other type of data is not curves, it is a faceted polygon mesh, just triangles and quad polygons like for example what is exported to OBJ format from MoI normally.

There are actually several different types of objects that can be stored in .3dm files, like NURBS, polygon meshes, lights, annotation dimensions, ... MoI will only read out the NURBS objects right now.

- Michael