I can't tell you what is different since I just got Bryce 4 late Spring, but here are the object extensions. Imports .COB (TrueSpace), .VSA(VideoScape), .WRL (VRML1), .LWO or .LWS (LightWave), .HF(Heightfield), .DEM (USGS DEM), .DDF (USGS SDTS), .PGM (Portable Greyscale Map)--don't know why they don't list .RDS, .3DS, .DXF or .OBJ, cause I import them all the time (took this info from Bryce 4 manual, pgs. 434-5). Export All the above, I believe, plus .ID4. Hope this helps. Diane