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The Roto brush is one of those amazing tools that can take a tedious job and make it more than bearable. And in our example, we're going to use the Roto brush to isolate our snowboarder from this background. Now, to see what we're dealing with, let's run a RAM preview of the video clip. It's pretty shaky footage. And the fact that it's a white snowboard on a white background sometimes would be a little bit frustrating. But, I'm going to press this space bar and stop playback here.
Let's start at the beginning of our timeline. Press Home on your keyboard. Now with our current time indicator at the start of our composition, double-click layer one to load it into the Layer panel. As a general rule, when you go to apply the Roto brush, you want to be working at 100% magnification. I'm going to press the Tilde key in the upper left corner of our keyboard. That'll maximize this panel. And if you press Shift+ Forward slash, that'll maximize our view in the scene.
Now it's only at 82% based on the magnification of my monitor, so I'll go ahead and just increase this magnification up to 100%. And since I know what I'm trying to isolate is in the lower left corner, I'll just press the space bar to grab my Hand tool, and move up to my lower left hand corner. The Roto brush toll is towards the right side of your toolbar. It looks like a little guy and a paint brush. If you click on it, that will select the tool and you can see our brush. To adjust the size of the Roto brush, you can press Cmd on the Mac or Ctrl on Windows, and then left click and drag up to make it larger. Drag down to make it smaller.
I want to make it relatively large, and then I'll start by clicking on my snowboard and drag around. Now, I don't need to go all the way out to the edges to make my initial selection. I can just click and drag down the inside. And when I let go, the Roto brush will automatically try and figure out the edges of my stroke. Now before we go on and start dealing with multiple frames, we should refine this brush stroke. See how in this area is hasn't quite selected enough of his leg.
So, we can go ahead and click and draw with our brush, just over the edge of that stroke. And then, it'll go ahead and add to the selection. In areas like here, in front of the knee, if you hold down Option on the Mac or Alt on the PC, you can draw a stroke over that brushstroke. Again, you don't have to go right up against the leg and let go. Since that decreased the size of what I was looking at, it did a relatively okay job. But I need to get a little bit more detail in here. This would be the time when you want to have a smaller brush stroke.
So, press Cmd on the Mac, Ctrl on Windows, left click and drag down to have a smaller brush. Now hold down Alt or Option, and then click and drag and you'll get this minus brush stroke. Once we draw through that, here you can see it's done a much better job of isolating this area. You could be as picky as you want, but once you get something relatively close, you should be relatively good with that one area. Now, I'm going to continue adding to the stroke here, over the snowboard. And down here on this right side of the snowboard. I don’t know about you, but I’m kind of impressed at the quality of the selection. If you look down at this lower part of the board, it doesn’t have very much contrast between the two different sections.
It’s a white board on white snow yet it’s still managing to find edge. Press Page Down to move down one frame. Now that we've moved one frame down, you can see the Roto brush has adjusted for the scene and attempted to redraw another successful stroke. You'll have to make adjustments, like here at the tip of the board. I'll go ahead and just click and paint over that one area just to get that one extra section of the board. Each time you make an adjustment to a stroke, the Roto brush will propagate down the timeline. So, to show you what I mean, if you look in the lower left corner of the timeline, you'll see this light gray area and these hash marks. This is letting me know the number of frames that the Roto brush has loaded based on my initial key selection.
My initial key selection is noted here by the yellow dash. Now, what I recommend yo do is to keep going down your timeline by either one frame at a time or every couple of frames, and then stopping. So, I'm going to press the space bar just to move down a couple of frames. Notice the Roto brush is doing a relatively good job of making adjustments. But on occasion, you'll want to stop and make a correction. Let's say I want to de-select this area. I'm going to hold down Option, and click and draw across. Every time you stop to make a selection, the Roto brush is going to populate more frames down the timeline.
It's loading individual frames or groups of frames like this because it takes a lot of individual processing power to figure out how to select these areas. Now once you know you have a group of frames you want to save, you can go ahead and freeze those frames. Go to the right side of your Layers panel and you'll see a Freeze button. If you click on that Freeze button, that will go ahead and freeze those frames into your cache. So, it's not always trying to recompute those selections every single time you look at those frames. Then, once you've got all your stuff selected and everything cached off to freeze, you can get ahead and render out.
Either image sequence or a QuickTime movie or Windows Media with an alpha channel. That would allow you to then input that footage into your future projects and place it over any background you see fit. I think, it's a heck of a lot easier than having to do it frame by frame manually using old school Roto techniques.
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