Depict “slow-mo” using expressions

[Walter Soyka]

[Darby Edelen] “I suppose that is another option, but it would require the same number of keyframes as keyframing the rotation plus another step :)”

I only mentioned it because sometimes adding that extra layer of abstraction is useful. With time-remapping, you could set the rate of rotation inside the precomp, which then makes your time-remapping cues relative, not absolute. You can change the underlying rate of rotation separately from the relative changes in rotation rates.

Sometimes this is more hassle than it’s worth, though, and in this case I’d probably just use rotation keyframes, too.

But Ryan, whether you use rotation for direct manipulation or time-remapping for indirect manipulation, the speed graph view in the graph editor [link] will be immensely useful for you.

You may be familiar with the value graph, which shows how the value of a property is changing over time:

ae-valuegraph.jpg

But there’s another option, called the speed graph, that shows the rate of change (derivative) of the underlying property. Here, the slope of the graph represents the rate of change of speed; therefore, a line sloping up represents acceleration, a line sloping down represents deceleration, and a flat line represents constant speed.

I keyframed the rotation of a shape here, and here’s the speed graph. It shows the rotation steady at around 720 degrees per second for two seconds, then decelerating down to around 75 degrees per second:

[ae-speedgraph.jpg

Here’s how to toggle:
ae-graphtypeoptions.jpg

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
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[Ryan Hannebaum]

Very interesting! I was not aware of the speed graph, but that sounds exactly like what I’m trying to do. Would it be possible to incorporate the speed graph on a Null Layer with Slider Control, so that I can speed up or slow down multiple other layers with one change?

Also, now that I’m able to get rotation to behave how I want, is there a simple way to do the same with Wiggle()? I have a couple layers that wiggle their rotation with:

wiggle(1,360,0.5)

…but I’d like to slow that down too. Similar problem to simple rotation: once the timeline gets to the slowed down keyframe, the wiggle slows down appropriately (I change the 1 per sec to 0.1 per sec in the wiggle expression). But between the 1 and 0.1 keyframes, the wiggle goes crazy, and doesn’t progressively slow down.