OgleEarth posts on SOLA G2, a free program (PC/Mac; free for non-commercial uses) for converting 3D objections in a number of standard formats into Google Earth KML files:
- Autodesk *.FBX (2006.11)
- 3D Studio *.3DS
- Wavefront *.OBJ
- Autodesk *.DXF
- Collada *.DAE
- Should also work with objects created with the free open source 3D program Blender, as long as you export them in a compatible format.
Select a filetype, choose the location, units and orientation, and SOLA G2 supposedly does the rest. I say supposedly only because I don’t have any files to test it out with; feel free to post your results in the comments below. You can also download the legacy version 1.0 of SOLA in case you have problems getting good results with version 2.0.