Check my book
http://www.packtpub.com/unity-for-architectural-visualization/book
or my video tutorials
http://www.packtpub.com/building-architectural-walkthrough-using-unity-video/video
for some answers.
Apart from the shameless self-promotion, let me try to give some answer here as well:
I have most success by using the Cinema 4D Exchange Add-on, to transfer the ArchiCAD model into the C4D format and either allow Unity to convert to FBX in the background (by placing the C4D file directly into the Unity assets folder) or by doing it manually by exporting an FBX file from Cinema4D.
I do encounter occasional glitches with some objects having badly mapped textures when arriving in Cinema4D.
If you don't have Cinema 4D (which is still expensive), you can indeed try to fall back on 3ds or obj formats, but they provide certain limitations. Ensure you enable the option to write texture information with the 3ds export.
You could try to export into Google Earth format which is Collada-based and is also supported in Unity.
--- stefan boeykens --- bim-expert-architect-engineer-musician ---
Archicad28/Revit2024/Rhino8/Solibri/Zoom
MBP2023:14"M2MAX/Sequoia+Win11
Archicad-user since 1998
my Archicad Book