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All right. Let's clear Nuke and take a look at the Addmix node. The Addmix node is actually used to adjust the edges of a composite. If your edges are too dark or too light, the Addmix node can save the day. Let's see how it works. We will come up the Merge tab and get an Addmix node. Now you notice it has an A and B input and no mask input. So, the Addmix node only gets a foreground and a background. To show you how it works, let's set up a special test.
We will come up to the Image tab and get a Constant color node. I am going to set the Constant color node to red, like so. All right. That will be our background. We will come up here. For the foreground, we will get a Bezier node. Type P on the keyboard and we will just throw something up here, connect that to the foreground, hook our viewer up. Now I want the Bezier to be pure green. So, we will come up to the Bezier node. Turn off the red and blue channels.
Okay, all right now to get rid of the spline I am going to turn off the overlay by typing O on the keyboard. I also want a real soft edge to demonstrate this so we will come up to the extra blur and dial that up. It gives us big, fuzzy edge and we will zoom in. So, let's clear the Properties Bin and double-click on the Addmix to put him at the top. All right. So, here is our setup. The green is the foreground and we can see here he is in the green channel and the red is the background, which is in the red channel.
We will switch back to the green, or foreground, channel. The idea is with the Addmix node you can adjust these curves to adjust the roll off of the foreground or the background independently. The roll off is affected by the Alpha channel edge. So, here is our A curve. To select them, you click on it. Here is our B curve for the background. Click on that. So, I am going to select the foreground, the A curve.
I am going to insert a control point with Alt+Command+Click and now in the Viewer, we are looking at the green channel, which is the foreground, and now as I adjust this curve, you could see the edges are dramatically affected. We are adjusting the roll off of the foreground edges, okay? We will switch over to the red channel, the background, and I will make the same adjustments and you will see that the background is completely unaffected by the foreground curve.
Okay, now we have the background in the viewer. I am going to select the background curve, insert a key, Alt+Command, and I will adjust that one and you can see that the background edges are now affected. So, the Addmix node will do the composite and then it will allow you to adjust the foreground edges and the background edges separately. You can make the foreground edges darker or lighter, and the background darker or lighter, either way you want to go.
Now let's see how it works with a real image.
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