I made an .OBJ object (a breathing set) divided into groups and materials. The materials are not the same as the groups. WHen I imported it into my Bryce 4, Bryce 4 dropped the material names and used numbers instead. That is pestiferous. E.g. its pressure gauge contained 3 circular materials, nearly coincident: back, dial, glass, and in Bryce I had to select the glass to make it transparent. And it was the devil's own job isolating the glass, because ctrl-leftclick only showed in the menu several entries "prgauge and a number".