Hi Mathias Buehler
thank you for you answer.
in the last week, i tried all possibilities ( export every layer alone, every building,export in other format like KMZ, COLLDA, AUTOCAD and OBJ ) and everytime i had the same error, but when i tried with a other projet the export worked.
i'm sure that there are something wrong in my projet i could't know it
regards
AMIRI