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Slider Expression to Control Influence of Parent.

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Dustin Bowser
Slider Expression to Control Influence of Parent.
on Sep 1, 2015 at 5:57:48 pm

I believe I've come across this before in the past, but can't seem to find it anywhere at the moment.

I have something that is tracked to a piece a footage, via parenting to a Null. What I would like to do is be able to animate a slider to lessen the influence of the parenting until the layer is not being tracked at all.

Thanks for any help!


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Dan Ebberts
Re: Slider Expression to Control Influence of Parent.
on Sep 1, 2015 at 10:41:45 pm

What determines the layer's position when the influence slider is at zero? Are you just talking about position?

Dan



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Dustin Bowser
Re: Slider Expression to Control Influence of Parent.
on Sep 1, 2015 at 10:53:27 pm

Basically I want something to go from being tracked, all the way to not being tracked.

What I'm doing is placing a composite element within a shot that morphs to something from within the plate itself, so at first it needs to be tracked in, but then when the morph happens it needs just be exactly as the underlying plate is with no added animation, but I have to hand between these two moments seamlessly

The tracking data is position, scale, and rotation.


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Dave Docimo
Re: Slider Expression to Control Influence of Parent.
on Oct 2, 2015 at 3:21:43 am

I have the exact some problem as Dustin. Hopefully there is a solution out there.


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James Paulley
Re: Slider Expression to Control Influence of Parent.
on Apr 24, 2018 at 3:41:54 pm

Did anyone ver get anywhere with this?


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Dan Ebberts
Re: Slider Expression to Control Influence of Parent.
on Apr 24, 2018 at 7:27:45 pm
Last Edited By Dan Ebberts on Apr 24, 2018 at 7:32:10 pm

It's tricky because, if I understand the question, you want the parented layer to keep any accumulated movement that was based on previous values of the slider. If that's the case, the only way I can think of is a brute force, frame-by-frame integration, something like this:


pos = thisComp.layer("leader").transform.position;
pct = effect("Slider Control")("Slider");
dAccum = 0;
f = timeToFrames(time);
for (i = 1; i <= f; i++){
t = framesToTime(i);
cPct = pct.valueAtTime(t)/100;
dAccum += (pos.valueAtTime(t) - pos.valueAtTime(t-thisComp.frameDuration))*cPct;
}


It could get bogged down if your comp goes on for quite a while.


Dan



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Kalleheikki Kannisto
Re: Slider Expression to Control Influence of Parent.
on Apr 29, 2018 at 2:33:32 pm

It seems to me that you should be able to fade between the position, scale and rotation properties of two nulls with ease using a slider to control the balance. That would give you the position, scale and rotation of a third null, to which you would have parented the layer of choice.

In other words, you'd create the tracked null and a manually animated approximation of the same motion that ends up in the final location that you desire. And then fade the motion between the two with a simple percentage calculation attached to the third null values.

That is, if I pictured your objective correctly.

Kalleheikki Kannisto
Senior Graphic Designer


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