thank you very much for your advice. my problem is as following: i am not the guy who is coping the two movies together. i just have to make the movies for the animation. so i am in the position to make two movies, one for the alpha, one for the play. that is too much. (capacities) So my question went the way, how to do it, without rendering the file twice... i will try your advice, but i think, it will take too much time... thank you and until soon benjamino