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Using the Roto Brush to create your initial selection is only the first part of the battle. In order to get a polished finished element out of the Roto Brush. You need to actually do a little bit of polishing using some of the different refinement tools available. We're going to start by looking at the Roto Brush Composition. So if you don't already have it open double-click on the Roto Brush Comp to open the project. And then double-click on the Board Ride layer in that composition. Now working with the Rotor Brush you typically want to work it 100% magnification.
So we are looking at 100% of this image right now. And I'm just going to Click and Drag down to hide part of my timeline as we sort of analysis what's going on in the scene here. Now the refinement tools for the Roto Brush are in the Effects Control panel. If you don't have this behind your Project panel, go up under Window and make sure that Effect Controls is active. If you open the Roto Brush Matte options, here you'll see I have Feather, Contrast, Shift Edge and Reduce Chatter.
I haven't gone through the entire length of this clip, then painstakingly painted the individual selections of the Roto Brush. That's part of the process of using the Roto Brush. Just making sure that you have your initial selection. But I do want to show you that first couple frames here in my Span. Let's say this is looking relatively close to what I want. Well I want to refine the selection of this edge. How do I know whether or not this shift is something that I can fix using one of these controls? Well, it just takes some getting used to working with the tool. As I'm watching, let's say the inside of this pant leg here, as I scrubbed through, you can see but it's holding the edge pretty well. Based on the distortions that are happening in the fabric. If you click and drag on this bottom parameter here, this is called Reduced Chatter.
What this does, is it changes the variation of the selection between the different frames. The higher the number, the less the variation is going to change. So you'll see less quote unquote chatter. I want you to look at the front part of the leg as I scrub over these frames. Even though I've increased the Reduced Chatter number, it thinks this part of the selection is something that I meant to do. So it's never going to smooth that out. But the slight variation that's happened along the edge of the fabric in this specific instance, it definitely has smoothed out.
Notice I can see a little bit of blue under there. That's not a good thing in this specific instance, so I may want to just decrease the Reduced Chatter amount, just to get that stroke a little closer to the edge. The rest of the adjustments all kind of play in tune with each other, so as you adjust one, you may need to go and make an adjustment to another. So this is when you want to quickly switch between these different view options. To view the Alpha, you can press Option+4 or Alt+4 on Windows.
Now the Alpha gives you a little bit better insight as to how quickly the edges of the mask are going to move. If you want to see an Overlay, you can press Option+6, and this will show you an overlay of what's actually going to get cut out. Now, sometimes it just makes sense to go to your Composition panel and look at your footage over top of whatever it is you're trying to composite. Since I don't have anything in my composition, I'm going to increase the view of my timeline and just add a layer solid behind our selection. So go up to Layer, and just choose New > Solid. I'm going to make sure it's the Comp size and then click OK. The fact that it's blue is fine, we can go ahead and drag it underneath of our selection.
I'm looking at the edge of this and I'm realising that it's rather jagged. But before I make a final determination I want to make sure that my Magnification is set to 100%. Now when I press the Spacebar to grab my hand tool and reposition, you can see it's really not that jagged. But I can go ahead and reselect Layer One and make adjustments to my Rfefined Edge selections in the Roto Brush Matte area. If I Click and Drag on the Feather selection, I'm softening the edge of the matte.
See this part on the inside of the knee? It's so soft that I'm actually getting some of the white poking out from underneath. If you make an adjustment to the Feather, you may want to consider adjusting the Contrast. The Contrast will get stronger or weaker as you click and make an adjustment. So notice, as I'm adjusting the contrast down, I'm starting to see more of the image here. That's because the feather is becoming softer, so I could decrease the amount of the feather here and notice now the line is tightening up to the edge of our leg.
I still want to have a little feather, so will set that to around 5.3. Now, since the edge here isn't quite as tight as I would like. That's when I could go ahead and shift the edge. If you make the number greater, it's going to go ahead and select more of the area. You can make the number smaller, and shift the edge in more closely to your object. Now, since we're kind of Rotoscoping a dark object. This change is kind of being magnified in this specific example. But all in all, I think this is actually generating a pretty decent mask for my isolation of this individual element.
Before you make your final decision as to whether or not this is truly good enough. You need to put in your finished graphics underneath and then render the file just to preview whether or not you like how it's mixing in. Obviously when you're trying to match a foreground element to a background element. Sometimes you'll probably want to consider using some other filters to blend those two elements together. Like, using some color correction techniques so the black levels and white levels balance between the two elements.
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