Ok forgive if this sounds a little confusing but maybe it won't.
I'm trying to light wrap some footage. The footage is filmed before a green screen so I have used Keylight to remove the background and get all basically looking like what you want a green screen footage thing to be.
Now light wrapping, I've never done it before so have been watching some tutorials on the internet, the only one's I can find are using pre-keyed footage so there is already an alpha without any work on their part. When they go through the process of Light wrapping they refer to the alpha channel a lot which I understand is an essential part to the process.
My keyed footage does not have an alpha channel though, its alpha channel is a big white space (not what i want).
Now this keyed footage does allow a different background to be placed behind it so the keying porcess has worked. Am I just missing a critical step or is something wrong with how i have keyed the footage?
Your alpha is generated by the keylight plugin. In order to do the light wrap you need to precomp the layer with the green screen WITH the keylight in it (move all attributes). This way you get layer with alpha and you can do a light wrap on it. Another solution is to render out just the layer with the key on making sure you export using an uncompressed codec like animation or a sequence of files tga or tiff, all supporting alpha channel.