Hi SIFF - I'm not that familiar with archicad myself, but I have heard of some people using MoI in combination with it, for example Rob mentions it on the forum here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=3101.1

I'm not sure what formats archicad can import though - does it support importing polygons from OBJ format? If so then that's probably what you would want to use.

This page here:
http://archicadwiki.com/TechNotes/Importing%20AutoCAD%20Solid%20Objects%20to%20ArchiCAD
describes how to import a 3DS file into Archicad, so that is another possibility. But 3DS files are triangles only instead of quads and n-gons, it is better to use OBJ format if possible.


Also check if it supports reading in any CAD solid modeling formats such as SAT, IGES, 3DM, or STEP. If it supports any of those, then you can use those formats which transfer the full NURBS surface data instead of only polygons. SAT and STEP are added in MoI version 2.

- Michael