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We know how to create and edit keyframes, but where the good animators end and the great animators begin is really determined between the keyframes. That's known as keyframe interpolation. You Flash folks might know this as Tweening. It's adjusting the changes between the keyframes. Now there are two kinds of interpolation to adjust in After Effects: temporal interpolation and spatial interpolation. The easiest way to think of this is temporal means time, so changes over time like Opacity or Scale.
Spatial interpolation means changes over space, like position. So let's go ahead and press 0 and look at a RAM Preview of our animation. I'm just going to press the Spacebar and stop here for a second. You can see we have our logo animating into the scene. And if you're joining me from the previous video, you might recognize this but think, hey, these first two layers look different. And they do, I just went ahead and trimmed the start point. If I select Layer 3 and press T to open up its Opacity, you notice I trimmed the layer to start at the first keyframe.
I'm going to press J and move forward so you can see this first keyframe is set to a value of 0. So before this keyframe, the Opacity was always 0, so there's no reason to have this extra layer here at the start. So I just trimmed the start point. This is a good habit to get into if you want to optimize your render times. Now move the current-time indicator back to the beginning of the timeline and let's select, let's say, this Yellow layer, Layer 4. Press U to open up any of its Animated parameters, and let's scrub in the timeline and see what we're looking at.
You can see we've got some different things moving on here, but I just want to focus on the animation of this yellow ball. So with the Yellow layer selected, I'm going to go ahead and solo that layer just by clicking this box right here in the timeline. All these other layers haven't disappeared, but this is just allowing me to focus on this one layer and not be distracted. Just so we can see things a little better, I'm going to zoom in just by using the scroll wheel on my mouse and press the Spacebar to move down so I can kind of center this up in the scene here.
As I scrub through, you can see exactly what's going on here. Now with these keyframes I want to point out something. Notice the Opacity keyframes here look like diamonds and these keyframes here don't. That's because these have a different interpolation. Now to see what interpolation is applied to a keyframe, go ahead and select the keyframe by clicking on it and you can right-click and go to Keyframe Interpolation. And here under Temporal, notice we have Continuous Bezier. See, I'm going to Cancel this for a second.
In the previous video we broke out the position data into both X and Y position. Now when we did that, by default, what After Effects did is change the interpolation from linear to that Bezier setting. So what we want to do, since we're going to be making changes in general, what I like to do is start with linear keyframes. So I'm gong to click and drag a Lasso around all these keyframes and right-click on one of them and choose Keyframe Interpolation and just change the Temporal to Linear.
Now when I click OK, you can see these are set to linear keyframes. To see how linear keyframes are represented graphically, what I want to do is move my playhead back to the beginning of the timeline, and let's click on the Graph Editor here at the top in the center of your timeline. Looks kind of like an X, Y graph. If you click on that, you notice I have two parameters: X Position and Y Position. Notice they're color-coded. Here is the X and here is the Y. Now, the graph is set up in an interesting fashion because this is the Speed Graph.
If I hover my mouse over the green line here, you can see it's moving to be exactly at 370 pixels a second. Down here on the X, it's moving at 0 pixels a second. Now the way this graph works, if I click only on, let's say, Opacity, it will show me the changes in the Opacity in terms of its velocity. If I click only on X, it's only going to show me X. If I click only on Y, it's only going to show me Y. Since the X position never really changed, it's set to a value of 0 over the entire time, because the object is only moving on Y, we don't need those keyframes anymore.
So I'm going to get out of the Graph Editor and just draw a Lasso around the X Position keyframes and press Delete. Now we can focus just very closely on what's happening on the Y parameter. If I zoom in a little more closely here, notice how these dots are evenly spaced in my graph. This is because it's a linear velocity, and if we open our Graph Editor here, you can see with the Y position selected, it goes from 370 pixels a second and stops in one frame down to 0 pixels a second.
What we want to do is ease the speed of this, and the way to do that, we'll get out of the Graph Editor and start with the first keyframe here. I want this to kind of speed up like you would in a car at a stoplight. When you stop and the light turns green, you accelerate from 0 gradually. So to do that, select the first keyframe, go up under Animation > Keyframe Assistant, and choose Easy Ease Out. I know this doesn't make sense, because it's the first keyframe, but you are easing out of its current state into a new velocity.
So now if you look, it's kind of hard to see, but the dots are a little closer together at the top, and then as you move down, they get further and further apart. Notice here at the bottom they stay far apart and just stop. So let's draw a Lasso around the second keyframe and instead of going back up to Animation, this time you can just right- click on the keyframe and go to Keyframe Assistant, choose Easy Ease In. We want to ease it back into its current state. So when I say Easy Ease In, okay, there you go.
Now you can see how close these two little dots are. And now if you look up here, these two are much further apart. So this is actually going to ease the motion. If we press 0, you can see it slowly came to a stop. Let me zoom out here so you can see this. We'll fit back to 100, and let's check out the animation again. There we go. It's a lot more natural motion. Now let's select the Blue layer here and press U to open up its keyframes. I want to open the Graph Editor one more time.
If we select the Y Position keyframes here, notice how the velocity starts at 0, eases up to a high velocity of around 550, and then eases right back down again. See, if I select the Y Position keyframes here, that had those funky eases on them, notice the velocity is very strange in how it moves. That's one of the reasons why I like to actually start by changing these keyframes back to a Linear Interpolation.
That way when you look at it in the Graph Editor, you can see exactly what's happening here. If I want to make these adjustments, I can just right-click directly on the keyframe, and make sure my first ease is out and my second ease is back in. Now if I select the Y Position in the Blue layer and look in the Graph Editor, you can see I've got the ease there as well. I want to encourage you to keep going through the rest of the animation and easing your keyframes. That way when you're finished, you can see just how more natural the motion of your keyframes are going be when you pay attention to your keyframe interpolation.
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