I'm trying to accomplish something specific:

I want to be able to take one video track and overlay a second video track on top of it. Here's the tricky part (or maybe not), the overlay position and shape needs to move as the video plays.

For example:

The main video could be an individual walking down the street and he passes a billboard - the overlay needs to fill the billboard, and presumably change shape/size/position/perspective as the main camera position moves down the street.


I don't need to be spoon fed the instructions, I can probably pick up the concept from some basic pointers. I just basically need to know what this is called, and what software can do it. Can After Effects 7 do this? Is there a better alternative?

After effects can do this and probably there is more than one way to do it. I'm still only doing fairly basic stuff with it myself but I would think that one way would be to mask out the billboard area and have your second track underneath show through where the mask is.

Then just animate as necessary as the first track moves along.

hope this helps point you in a possible direction

Yep, tons of way of doing this. Generally easy to 'map' the image to the billbopard and have it move across the screen. getting it perfect may need some serious keyframing though.

The problems get really difficult though if your foreground character actually walks in front of the billboard obscurings parts of it from view.

There's two issues here, mapping the billboard to move as required and then masking the person in the foreground. I've (sort of) attempted both of these on occasion (although I neve combined them).
I mapped a previous video clip over a TV screen so it looked like it was playing. I simply used a corner pin to do this. Keyframe your corners as often as necessary to get a convincing move across the screen. I hope you used a good trippod for the pan or you could find yoursefl keyframing nearly every frame.

In one of my movies I had the main character walk in front of the movie title. Not quite convinced I did it the easiest route but I rototscoped it in Photoshop frame by frame by overlaying the graphic and then masking the person on each frame.

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