Hi Romin, There can be several causes for a 3ds file not exporting properly. Make sure that all faces you apply the materials are front faces (whitish) not back faces (bluish-grey). Then also, make sure that your material names do not contain any other characters than the English ones (not even spaces are allowed) and they are only 8 character long with the three character extension (I doubt you can remember when every file had this limitation).