Extracting Reflections??

I have a bit of a problem...

Basically I have a film footage background with mirrors in , the real camera pans across the room and mirrors are on the far wall. A CG character walks along with the camera pan, he obviously needs to be seen in the mirrors.

So far I've made a poly plane with a reflective material to get a reflecton and put it over where the mirror goes in the footage.

Is there anyway to get an alpha around any mesh being reflected on the plane? so that I could just have it as another layer in post?

Thanks for any advice

Add a white surface shader to everything in the scene, except the mirror. Put a black surface shader on the character. Leave reflections enabled on the mirror, so it will reflect everything as white, except the character will be black.....reflection alpha...

THANKS DiGiman !!

I thought it would be somthing like that, I've been working on these shots so long I cant think properly

What i did in the end was to turn the character white and turn off his primary visability. Then I made sure the environment was black and rendered the frame with no alpha channels. That gave me a black image with just a white sillouette of what the mirror could see.

Then I rendered the same frame with the characters normal material, still no primary visability and again no alpha channel. That gave me a black frame with the characters reflection only.

I can use a stencil layer in combustion to add the two together and stick them over the film footage.

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