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| Difference mattes have gotten more useful with the advent of high-quality digital cameras, but still rarely work. It's easy for your brain to say "look, the actor is in one plate but not the other," but the computer can't tell what's an object and is only looking at differences in color. If your actor's skin tone is similar to the shelves behind him, you're hosed. I would look into the roto brush like Jack said, and maybe give the Furnace tools from the Foundry if you have access to Nuke. If not, I'd bite the bullet and start rotoing. If your actors are *really* flailing around, hand-painting the mattes may be quicker than yanking splines around. $.02, Brian On Sun, Nov 4, 2012 at 4:19 PM, Teddy Gage <teddygage@gmail.com> wrote: Hello, I'm working on an indie film and they have presented me with some "interesting technical challenges," to put it diplomatically. The current shot I'm working on is two actors getting riddled with bullets, with no practical effects or greenscreen. I am adding blood, bullet holes, dust, smoke and glass. they are flailing about like rag dolls then go down. It lasts about five seconds. There are rows of shelves behind them with glass bottles that stay intact throughout the shot. In a separate shot, the director then pulled the bottles off the shelves using strings, and the two shots need to be composited together. If only the actors had been shot on greenscreen, this would be easy. But there are enough changes between shots that a difference key only gets me about 50% of the way there. However this ancient effect is not 32-bit, has awful controls, and it's almost impossible to get a clean difference matte; half the background is pulled into the effect and I cannot cleanly separate the actors. |
