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Now I am not trying to pull great keys here, as that is a time-consuming process. I'm focusing on showing the workflow for combining several keys into one master key for compositing. So I'm going to just pull some quick and dirty keys here. So let's give me a little more table space here. I will select the Roto node. So I am going to use the Primatte node here to pull a key for the body. Let me reset the viewer back to normal settings. And we will select our background color. Now I better connect my viewer up to the Primatte node right here. Here we go.
Okay, now we will take a look at the alpha channel. Then I am going to refine this by cleaning the background noise like so, sample it here. Then I'm going to clean the foreground noise by sampling here and there. Again, I do not care about the head of the hair; I only care about the shirt, slide my view again down to make sure I don't have any unnecessary holes in my shirt. Yes, I do, so clean those up too. All right, again, try to make a good shirt.
I don't care about the hair or the head. Set my viewer back to normal and slam the gamma in the other direction, so now I can clear the backing region, select BG Noise again, sample there and there, over here, there and there. Okay. Let's say we liked that. We will set our gamma back to normal, re-home the viewer. So let's say we are happy with the key for the body and to help keep things clear, let's label the Primatte node body.
Next, we will use a different keyer to pull a key optimize for the head. Let's say that I want to use the Keylight keyer, okay, hook that up, attach our viewer to it, switch to the RGB channels, and I will start by selecting the green screen backing color. There we go. We will switch back to our alpha channel, and now I will start dialing in the Keylight keyer. The important thing is I'm only concerned with the head region.
I don't care if there is problems down here in the body. This is the beauty of this thing. Well, I will dial up the screen gain a little bit, and I have still got a little bit of stuff over there. Let me check that I don't have any holes by raising the viewer gamma, check for holes in he head. That looks good. And then I will lower the viewer gamma, checking for any other issues. All right, that looks fine. I want to get rid of this over here because that is part of the head. All right fine. So I will go to the Screen matte, and I will dial in the black clip to get rid of that.
Okay, let's say we are happy with that as a key for the head. Again, to help keep things clear, we will label the node head. Okay, now we have a Primatte key for the body and a Keylight key for the head. Next, we need to combine them some way. So I am going to combine the good body key with the good head key, and to do that I'm going to use a roto. I'm going to draw a shape around the head and use that to separate the head and the body and then join them together.
Now a very important point is where you place the split. I'm going to choose to make this the joining line right across the neck here, because that's easy to hide and easy to animate. Because we have a moving target, we are going to need a few keyframes. So I want to select right across here and then around the head, close that. Now if we look at the Roto, we have this mask and we have our head mask. So the next question is, how do we cut the head off using this Roto as a mask? For that, we are going to use the ChannelMerge node.
The ChannelMerge node was made for doing alpha channel manipulations. So I'm going to connect the A side to the Roto, the B side to my key, and my viewer to the Merge node. Now that does not look very promising yet. What I want to do is I want to keep the head key that is inside the Roto. Now the problem is these are hooked up backwards, so the order of connection is very important. So I'm going to switch, instead of A and B here, I want B and A. Okay, you will see why in just a moment.
So I will switch those with Shift+X, because I want the operation to be A inside of B. So I need the inside operation, so I will come up here to the operation. Let's set it for inside, and there you have it. I now have the head matte that is inside the Roto. And I want to use the exact same Roto for the body so that the seam is always perfect. So next, we need to go over to our body and get the body key that is outside of the Roto, and for that, we need another ChannelMerge node.
So, go up to the Channels and select ChannelMerge. Now I want the body outside of the Roto, so I want A outside of B. I will hook the viewer up to the new ChannelMerge node, and I will set the ChannelMerge operation to out. There we go. I am going to clear the Property bin, so you can see we have just the body outside that Roto, and over here, just the head inside that Roto. And because we used the same Roto for both, we are guaranteed a perfect match at the seam.
So, in order to merge those two keys together, we are going to use of course another ChannelMerge node. I will come up here to the Channels tab, select another ChannelMerge, bring it down here. Maybe I will zoom out a little bit. Since we are going to be joining these two together, the order of connection is not important. So I will just hook these up, connect my viewer to here, and take a look at what we have got. Whoops! We seem to have a little problem. Right here at the seam, we have our perfect head key and our perfect body key, but the scene which came from this Roto and the inside and outside operations here, that's caused an artifact.
That's because our operation was a union. The union operation is like a screen operation. This is not the operation we want. So let's take a look at saying plus. There we go. We have now added together the two mattes so at the split edge they are now a perfect match. You have to be careful when using the plus operation. Because you can add two mattes together, the 1+1 can then become 2, which you do not want; you always want to keep that. So we are going to sample right down here and keep an eye on this right there.
Make sure that we have not introduced any code values above 1 in the alpha channel. Okay, that looks great. If we did, we would go up here to the Color tab and add a Clamp node to take care of it.
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