I have a picture of a game and the picture is a user created spaceship with terrain in the background(trees, grass, rocks, water, etc.). I want that spaceship to look as it were coming from the sky. How would I do this? Would I use the Pen Tool to make evreything outide the spaceship(outline of it) green, so it seems as if I made the spaceship with a green screen in the back? Or would I have to take the picture, render onlly the spaceship out in Photoshop and then get a video file of the same terrain and place the rendered picture in front of the video? Which way would be the easiest? Also, I am not very good at all with Photoshop, so if you suggest that way to me can you tell me how/what tool to use and how to import it into AE Cs5(I know the some of the basics of AE Cs5 and basically nothing with Photoshop). Thanks. If anyone needs anymore info on how to help me, please comment.
If you use the pen tool to create a mask around the space ship there is no need to make the background green, it will be transparent. Just place your sky layer below the spaceship layer.
Read up on masking in the help files.