show more Overview provides you with in-depth training on 3D + Animation. Taught by Steve Wright as part of the Nuke 6 New Features show less
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I have said many times that you cannot expect to plug your green screen or blue screen or background clip into a keyer node, tweak a few knobs, and get a fine composite. That only works on the demo footage. In the real world you have to pull multiple keys and merge them together into a single master key. Here we will see a variety of strategies for creating and combining those keys into a single master key. The reason you want to combine multiple keys into this master key rather than compositing each keyer output on top of each other is because that makes a patchwork composite with different appearances of the spill suppression and color corrections from each keyer node.

The Primatte output simply looks different than Keylight. So let's take a look at the workflow. Starting up here with our green screen, the first thing we do is pre-process it to set it up for the keyers. One obvious method here is of course degraining. Down here are the different keyers. These could be completely different kinds of keyers or the same keyer with different settings. For example, Primatte here optimized for the head, Primatte there optimized for the body, and maybe Keylight here optimized for the hair.

Down here is where all the keys are combined to create the single master key. Of course, this is a very complicated and important thing, so we will be taking a very close look at those in the upcoming videos. On a separate branch from the green screen we do the spill suppression. The PreProcess green screen is never used on this branch. The PreProcessed is only for pulling keys, okay? So here we do our spill suppression followed by color correction. Always in that order.

You never put the color correction before the spill suppression. The reason is, if you change the color correction and then the spill suppression follows it, it will completely mess up your spill suppression. You'll have to do it all over again. So always in this order please. Here, we are combining the single master key with our color-corrected and spill- suppressed RGB foreground right here. The reason is we want to put them all together into a single RGBA four-channel image for the AddMix node.

It expects all four channels right here on the input. We are using the AddMix node because it has powerful additional features of being able to adjust the edges with those curves. If you don't need those curves, you could use a KeyMix node or do a premultiply and do the merge over. We will be looking at those workflows as well. Now that we have an overview of the general workflow, it's time to take a look at the specific techniques for creating and combining multiple keys into a single master composite.

Video duration: 2m 42s 4h 6m Intermediate Updated Feb 13, 2012


Overview provides you with in-depth training on 3D + Animation. Taught by Steve Wright as part of the Nuke 6 New Features

3D + Animation Video
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