Help! Tack Layers Problem
 

Ok. I have a beautiful animated Planet Earth on a black background. I also have a Jpeg starfield, an image matte with the white where the Earth should come through and an 4th jpeg for atmosphere.
All have black backgrounds.
How the hell do I get the Earth globe to come through all those and leave the starfield as the background. I am trying all sorts of combinations putting them on different tracks and pressing all sorts of compositing buttons but cannot get the desired effect.
I just know that someone out there will come back and solve this little dilemma in seconds, please??

put the earth on a layer above the starfield, and luma or chroma key the black out of that layer.

Thanks Bill. Is it really just that though. I would have thought there was a better way using the compositing modes Vegas has and depending on which event was on which track. Simply chroma keying out the black seems rather at odds with Vegas's capabilities.
I did as you asked but there is a distinct effect on the actual globe itself in terms of colour change.
Is there no cleaner way?

I have added these pics to show wht I am dealing with.
The video in addition is a full colour Earth globe on a black background

that was the simplest way,

You could add an alpha channel to the globe file in something like Photoshop, and then save it as a .png so it retains the alpha information. you might have to invert the alpha or use as is when you import, it all depends upon how you create it.

You didn't post the earth jpg, but I gather there is black in in and that too is keying out when you key out the background black.

hope that helps.

I went and used the circular cookie cutter which worked perfectly.
I will try various scenarios Bill but thanks for your help anyway.
Chromaing was just a little bit off because of the black part on the Earth.
Maybe I am trying to be over simplistic; it's a failing of mine!
Cheers

Try this veg file (for VP8).
Replace the generated media with your animated Planet Earth.

Gilles, thank you, that is exactly what I was looking for. I note you have the ATMOS track set to "screen" I did not even try that.
Great Stuff

I can't believe the one major difference is applying the Mask Generator at Track level rather than event level. I don't know why it works but it does.