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Discover how to manipulate time in After Effects. Author Chris Meyer shows how to stop, slow, and speed up footage, and how to combine these techniques with nested compositions, expressions, and the Graph Editor. Along the way, he reveals several important yet somewhat hidden functions, such as the advanced composition setting that ensures predictable stop motion, the Frame Mix and Pixel Motion modes of the Frame Blending switch, and the Time Remap parameter.
The After Effects Apprentice videos on lynda.com were created by Trish and Chris Meyer and are designed to be used on their own and as a companion to their book After Effects Apprentice. We are honored to host these tutorials in the lynda.com Online Training Library®.
As usual, we'd like to challenge you with a Quizzler, just to see how well you're assimilating the things you're learning in these lessons and to get you thinking on your feet for when a client asks for something that might otherwise seem impossible, but which After Effects can actually do. Inside the Quizzler folder is a comp called Quiz_Looped Comp*starter. I'll double-click it to open it and I see that I have a composition already nested inside this composition. Let's scroll through it. It just runs out before the end. Let's go ahead and double-click this comp to open it up and take a look at it.
I'll press 0 to RAM Preview. You might remember this composition from the After Affects Apprentice lesson on expressions; this was one of the Quizzler challenges in that lesson. At the end of that challenge we ended up with this looping composition with these pulleys rotating back and fourth. To make this loop seamlessly, we did two thing. One, for the main pulley that has a keyframe to action, we made sure that the pulley came to a stop at the very beginning of the composition, double-checked what its rotation was, 0 degrees.
Then we went to the end and one frame past the end, because one frame past the end is this is same as coming back to the start, and made sure it came to a stop and also had the same value as the first keyframe. The other thing we did is we took a looping stock footage background, exposed the Stretch Column, clicked on the Stretch parameter, and made sure the duration of this clip matched the duration of our composition. This particular clip was originally 14 seconds and 19 frames long, but we needed a 5-second loop for this composition.
We entered New Duration. After Affects automatically calculated the Stretch Factor for us. Click OK. And knowing what we know now, we'd even enable frame mix, frame blending for that clip, just to make its motion that much more smooth. Even when you speed up a clip, frame mix still blends adjacent frames to create less stuttery motion. Okay, we have a perfectly looping pre-comp. How do we extend that looping pre-comp to fill out the length of this second composition? Well, there're a few approaches.
One is you can keep duplicating this comp and putting it end to end until you have the length you needed. The other thing you could do is you could render this out, re-import that rendered movie, go to its Interpret Footage dialog, then have that rendered movie loop as often as necessary to fill out your entire new composition. However, there is another solution that requires only one layer and does not require you to pre-render this composition. Your pre-comp would still be live if you need to do any changes to it.
And no, I'm not talking about slowing it down until it stretches out during the entire length of this composition. Keeping normal playback speed, how would you extend this animation to continue for the rest of the composition? If you want to figure this out on your own, just stop this movie now, because I am about to give the spoiler. Okay, you are still here? To solve this, you need to combine something you learned in the After Effects Apprentice lesson on expressions with something you've learned in this After Effects Apprentice lesson on time games.
You can put these two techniques together to go ahead and loop this composition in time, as long as necessary. Okay, now let's see if you can figure it out.
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