[Bret Williams] “The light wrap idea sounds great, but never looks anything but blurry. Probably for the reasons posted.”
Incidentally building a light wrap is really very straightforward.
It involves blurring the matte and then combining the blurred version with the original of the matte in order to create a edge that overlaps into the foreground. The amount of the blur determines the depth of the light wrap. This matte is then used to composite a blurred version of the background image back over the foreground.
This simulates the effect of the light from the background encroaching over the foreground edges as it does in the real world. It can really help a lot of green screen composites – but as with all things to do with keying it needs to be used with discretion.
The problem is that Apple haven’t executed the blur properly so as to crop it at the edges of the frame – as I say, it’s a really easy fix.
And pace Bill, not remotely computationally expensive.
Simon Ubsdell
http://www.tokyo-uk.com