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Speed expression with keyframes
I have a layer speed controller that works great without keyframes but would love to add keyframable speed. Here is what I have now:
spd = effect(“Slide Speed (px/sec)”)(“Slider”);
[time*(spd), 0];This makes the layer ‘slide’ at the speed set in the slider. Problem is that is I keyframe that value then the speed transition no longer works. How can I modify the expression so that I can keyframe the speed and the layer continues in the place but at a different speed?
replied 13 years, 8 months ago 2 Members · 3 Replies
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3 Replies
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Lloyd,
It sounds like you need a linear keyframe integrator:
https://www.motionscript.com/articles/speed-control.html#linear
Dan
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Hi Dan,
Thanks that is exactly what I was looking for. Should have checked your site! Love the new design by the way.
One note, though. If you use Hold keyframes you get a bump in the value graph:
Works great with linear keyframes. 🙂
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Lloyd,
Good catch. I didn’t really think about hold keyframes. You just have to replace the last line of the for loop with:
v2 = spd.valueAtTime(k2.time-.001);
accum += (k1.value + v2)*(k2.time – k1.time)/2;It’s a tiny bit less accurate, so I don’t think I’d use this version with linear keyframes, but it seems to get the job done for hold keyframes. I’ll have to update the article. Thanks!
Dan
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