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In the previous movie, I showed you the basics of creating a variable mask feather where I have my mask path and then I have a separate feather path I created using the Mask Feather tool. And just to make my mask path a little bit more visible against this orange and yellow piece of footage, I'm going to go ahead and click on the color swatch for my mask and give it a more obvious color such as something in the magenta range there. Now it stands out more against my blue background as well. The first option is very useful to know as you have some control over how the feather falls off between the start of the feather and the end of the feather, and that's set underneath Layer > Mask > Feather Falloff.
The default is called Smooth, whether it's kind of an 'S' shaped curve as the feather falls off from the start to the end. The other option is a Linear where it's a very mathematically precise fall off, starting at the one edge and ending at the other. And to see what these look like, I am going to go to Display, just the Alpha channel, and I'm going to solo my layer on top that has the mask so I can see better how this feather is falling off and what the Alpha channel looks like. I'm going to save the snapshot of this display and now I can change Layer > Mask > Feather Falloff.
When I choose Linear you'll notice a couple of things. One, the mask appears to be broader. It seems to reach further and get closer to this ending line. If I turn off the Mask Visibility, you'll also notice it has a rather sharp edge as it starts to fall off from the beginning of the mask feather to the end. Now there is no edge here, it's just a nice linear fall-off but our eyes tend to perceive those changes as almost a white glowing outline around the mask. I am going to go ahead and compare the smoother version of my Alpha channel where that edge is much more rounded, and the linear version of it.
As you can see, Smooth creates some more pleasing fall off, but the one downside of the Smooth shape is that it just not appear to reach all the way to your mask feather boundary. Therefore, if you use Layer > Mask > Feather Falloff > Smooth, you might find yourself pulling this points out further than you expected. You just can't pull them out to a piece of the underlying footage. I'll go back to RGB and expect it, to actually in there.
You're going to have to rely on the other half of your brain and see how that composite really looks. Let's play around with some more tricks. If you have a few feather points that are pretty close to each other to where you have a fairly sharp bend in the feather path, After Effects will interpolate between those points using sort of an Auto Bezier, or RotoBezier type of curve. However, just like the RotoBezier tool has tension on its corners, the same thing is true with the Mask Feather tool. If I hold down Option on Mac or Alt on Windows, I get a little tension icon to where I make the fall-off rounded or sharp.
Particularly, obvious on this top point where I would pinch it or round it out. If you want a mathematical control over what that tension is, right-click on any one of these vertices and you'll get Edit Tension which is a tension value, Edit Radius which is the length of that line, then Edit Corner Angle which frankly I haven't found has much use when playing with the Mask Feather tool. These two are the biggies. Select one, you'll get a Value dialog, if I will sync the feather radius to a larger value such as 70 pixels, and click OK, you'll see that line has jumped to be longer 70 pixels long to be precise.
Now one of the trick inside Mask Feather tool and you might have seen it, when I right-clicked on one of these vertices is Hold feather. You can create sharp staircase fall offs between feather points. You can use this pop-up menu to set Hold or there is a nice interactive way of doing it. Hover your cursor over your mask path, press the Shift key and it will turn to this cursor the two plus symbols, and a line between them. That means you're about to add a Hold segment to your feather. If you drag this out, you'll see a very sharp transition on this new mask feather point which was based on my mask vertex until I get to my next mask feather point. Same if I drag this out too.
When I create my point, there is a hard mask fall off until I reach my next mask feather point. This is particularly useful if you have one side of say a rectangle type of object and you want to feather that entire edge the same. You can just go ahead and hold the Shift key, click on that side of that box that rectangle that part of shape, and drag up the whole edge instead of having to drag out two points to fit the mask feather evenly along the entire edge. And just like with any other mask point, you can select them, Shift+Select to select multiple points or select a point and press Delete to remove a point.
I'm going to remove my hold of mask points which are identified by this special icon which just points in one direction. And I'll delete that one. So that's a quick lesson on how you use Mask Feather in a more graphical application like this fanciful composite I was creating. However, Mask Feather is also very useful if you are trying to create realistic composites of putting an image over brand-new background as if they were shot that way. That's what I'm going to demonstrate in the next movie.
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