Expressions/Scripts/Presets

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Atomic
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Time Accleration Woes

Thu Dec 06, 2007 7:03 am

Hi All,

I have been trying and trying to find a way to speed up the time of a precomp. It seems like a simple enough feature, I see it all the time. And maybe I am making this more complicated than it needs to be. But here is what I want to do.

Let's say I have a ten second precomp.
I time remap it to 5 seconds. It now is traveling twice as fast as it was.

What I would like to do is still have it start off at normal speed, but by the time it gets to the end of the clip it is moving (let's say...) four times as fast as it orginally was before the time remap. So 4x normal speed. I'm not stuck on 4x, just an example number.

I don't know how to write an acceleration formula. It could be simple, I don't need drag or friction or any of that. Let's assume the newtonian model of all things in vacum kind of accleration with the result of the formula being a frame number between the inPoint and outPoint of the layer the expression is applied to.

:cry:
 
Dan Ebberts
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Thu Dec 06, 2007 7:19 am

If you want to model graviational acceleration you could just use a time remapping expression like this:

g = .25;
g*time*time


Adjust g (gravitational constant) to suit.

Dan
 
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Atomic
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Thu Dec 06, 2007 11:56 am

Hi Dan,

That is close.

Here is my setup.
I have a comp with two layers in it. A text layer. A 50 frame precomp.

I apply this code to the text layer source text.
f = timeToFrames(time);
g =0.0003
"Frame: " +  Math.round(g*f*f)


I apply this code to the precomp Time Remap.
f = timeToFrames(time);
g =0.0003
Math.round(g*f*f)


The concept is that the text box will display what frame the time remap is displaying.

The odd thing is that this only displays half the frames. It seems to skip every other one. I suspect the round function may be eliminating half the footage. Using this code the composition displays images up to frame 25 (which is actually displaying frame 50).

Any clue :?:
 
Dan Ebberts
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Thu Dec 06, 2007 12:54 pm

Hmmm.... not exactly sure what you're doing, but it seems like you would need to convert from frames back to seconds.

Dan
 
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Atomic
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Location: United States, Ohio

Fri Dec 07, 2007 7:21 am

So Time Remap is expecting a "time" value, not a "frame" value?

I assumed Time Remap was expecting frames.
 
Paul Tuersley
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Location: London, UK

Fri Dec 07, 2007 7:56 am

Time Remap expects/requires time in seconds when using expressions.
 
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Atomic
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Location: United States, Ohio

Sat Dec 08, 2007 10:59 am

I guess, I was over-thinking it.

All I needed to do was to adjust the tangent handles of the time remap keyframes themselves to create a logarithmic curve.

No expression is needed.

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