You can certainly make movies with 3DGS. Movies are easier to make than games. You need to use file_for_screen to capture screenshots. With Virtual Dub, you can stitch all these screenshots together to form your video. Just set a frame rate (like 30 fps, the typical setting used with movies) and base all movements on that single frame rate. How it's done is that you first set the positions as needed. When done, use file_for_screen to take a screenshot of the game. Next, reposition the objects for the next frame and use file_for_screen again. It's the best method I know of.