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When I was preparing the Exercise Files for the last movie, I used a very important feature of After Effects that I want to share with you here. Now, you will notice that with the rear tire curls layer, if I press the letter M, there is no mask here. So, in other words, I can't use Mask Expansion. So, I need to make a mask out of these layers so that we can use the Mask Expansion feature. Now, there are two ways of doing this. One, we can go in manually and use a tool like the Pen tool and click, click and drag, and then manually go through, laboriously go through I should add, every single spot here and trace these curls, clicking and dragging, clicking and dragging.
But this is such a pain. So, what I am going to do is just delete that and show you what I really did. I selected this rear tire curls layer, then go to the Layer menu at the top of the screen and then choose from the bottom of the Layer menu, Auto-trace. This will go through and automatically trace and create a mask for your currently selected layer. I am going to check the Preview box here so we could see what's going on. This is kind of a preview of what's happening. I want to make sure this is set to Current Frame.
If I set this to Work Area, what's going to happen is that After Effects is going to trace every single frame and create new masks for every frame. We don't want that. So, I want this to be Current Frame only. Although I should point out, if I had a moving layer then you might want to set this to be the Work Area. I am also going to set this to be the Alpha. It's going to look at the transparency of the layer and draw masks around the transparency. And we could adjust these values, such as Tolerance. I could increase that if I wanted to. And you could see the effect that's having on my mask here.
But I think default value of 1 is going to be just fine here. And actually, the mask doesn't look all that great right now. But when we actually click OK with these settings, it's going to look better than the preview is suggesting that it will. Although, if I was picky, I could come over here to some of the other values, Corner Roundness, Threshold, Minimum Area and play with these a little bit to get the value that I like. I am actually going to take this back down to 50 or so for right now. And again, I am just going to leave this pretty much at their defaults. But if you wanted to tweak this, you could.
So, I am going to go ahead and click OK here. And basically, what that did is it made a new layer. See the curls look much better than they did in the preview. So, it created a new solid layer and applied the mask to that solid. So, what I need to do and what I did is to select the rear tire curls, the original one, and go to the Ramp effect on the original rear tire curls. Hit Command+C to copy or Ctrl+C to copy on the PC. Select the new solid layer, the Auto- trace Solid, and hit Command+V or Ctrl+V to paste the Ramp effect so that our swirls look similar to what we had.
I will select the Selection tool here, click away to deselect, and I will turn off the visibility of the rear tire curls original layer. Now, you will notice that, and this is the way it is with Auto-trace a lot of times. There are some weird little glitches. So, what I had to do in the last movie was to go in and select certain points and maybe delete them. And in this case, there is a kind of a little bump right here. I could just click and drag these points up to get back the original curvature of the curls. It's just kind of the nature of the beast, but what's easier for me, in my own opinion, is to go through and tweak this rather than to fiddle with those Auto-trace settings and just try to guess the right thing to do.
So, it's easier for me, again, because I like playing with these Bezier curves. It's easier for me just to do that than to get the settings right, right out of the gate. And actually, I need to drag this down below the Bike layer, so it's in the back now. So, the movie would be there. That's the Auto-trace feature. But I want to show you some other benefits of having a mask. Not only do we get access to cool features like the Mask Expansion and Mask Opacity and all that kind of stuff, where we could selectively choose the opacity of these different curls. But one of the other benefits is there are a lot of effects that use masks.
One of the most basic ones is Stroke. So, if I were to apply this, then what we could do is you will see that the Stroke effect applies a stroke to one of our masks. And we can't apply the stroke to just our regular tire curls. At least we don't have this much flexibility. So, Stroke works with masks. And I could choose selectively which mask I want to apply this to. So, there's that. Or as I am going to do in this case, I could check All Masks.
And so now all masks have a stroke. Now, you will notice that it's a little bit pixilated because I am zoomed into 200%. This is the regular zoom ratio. And as you zoom in above 200%, you are going to get that pixilation, even though these are Illustrator files. If we were to scale these up to above 200%, then it'd be fine. It would look great. But because we are zooming in above 200%, that's what is making this not look so great. Now, what's cool about this is that I can animate the Start and End values. It's kind of like we saw with Paint. So, I could take End down.
And so basically what its doing is it's tracing on this paint or this stroke, in other words. So, what I am going to do is I am going to set End to 0%, beginning of the composition or 7 frames in as in the case here, some time towards the beginning of the comp. Move out in time a little bit and then we will take the End value to 100%. And so now, if I click away to deselect this, zoom out to 100%, then preview this, we get a really cool animation of our curls being drawn on, at least the Stroke being drawn on.
But what we can do is we can go back to our effect here, and just like with painting, we can increase the spacing so we have a series of dots. So, now when it is being painted on, it's a series of cool little dots. And we can go down to the Paint Style parameter at the bottom of the Stroke effect and change this from On Original Image, so it is basically making the Stroke on the original image to On Transparent. So, now we just have a series of dotted curls and look how cool that is. Also, it looks like some marquee or something that you might find at a Broadway show or something.
Take Paint Style to Reveal Original Image. And what this is going to do, it's going to be just like On Transparent except it is going to take the original color from the original layer. So, now we have this really cool effect of these dots being animated on with the original color of the curls. Very cool effect with again minimal work. And this was done for us by the Stroke effect, and there are several other effects as well that use masks like this. So, this Auto-trace feature does become much more powerful when we realize all that masks bring to the table.
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