@ catlin: thank´s for quick answering!
I´ve googeled programes like "eagle" (Cad fo electrical use) use .idf-files too. I have to model a car for crash-simulation and they need .idf , .fce or .x61-files (things i´ve never heared of...). So I need a bridge from Rhino to one of them. Is it think progs like need-for-speed uses .idf-files for addons (think i´ve read something about it) ? If no one can help me, I have to build a paper-car and send it...
cheers
Edit
yes , idf is used in midi and in ecad too...
We´ve found a solution for my prob!