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Exponential Functions in AE Expressions
Hello. I am completely new to AE and recently began working with Expressions from scratch. I want a 2D object to scale from 10% to 100% over a modifiable length of time. However, I do not want the transformation to be linear and I don’t want to create keyframes since this effect will later be triggered by another layer’s properties.
begS=10;//initial and minimum scale
dK=.95//decay rate, must be < 1 xScale=begS+90-(90*(dK^time));// initial time + 90- a value that decreases with time from 90, never reaching 0. yScale=xScale [xScale,yScale] I suspect it's a noob's syntax or language issue because the formula looks right in a graphing calculator. Basically, when I use this expression the animation jumps around and begins at 100% scale. Anything to the 0 power is 1, so the scale value at time=0 should be: 10+90-(90*1)=10%. At time=1, the scale should be: 10+90-(90*.95)=14.5%... and so on. Thanks you for any help. I searched the forums and found no explicit discussion about exponential notation within After Effects Expressions. -
3 Replies
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[Roman Alvarado] “I searched the forums and found no explicit discussion about exponential notation within After Effects Expressions.”
You can use any JavaScript math functions in AE expressions.
https://www.javascripter.net/faq/mathfunc.htm
I believe the one you’re looking for is
Math.pow(a,b)Darby Edelen
Lead Designer
Left Coast Digital
Santa Cruz, CA -
Ha! I knew it was a simple mistake. That’s what I was looking for, thank you. I did manage to figure out a very roundabout solution to create a similar effect, but not as adjustable:
timeToFrames(t = time + thisComp.displayStartTime, fps = 1.0 / thisComp.frameDuration, isDuration = false)
timePos=((thisComp.layer(“Shape Layer 1”).transform.position[0])-position[0])/fps;
hxPos=thisComp.layer(“Shape Layer 1”).transform.position[0];
pPos=position[0];
sx=10+90-(90*Math.exp(-timePos));
sy=sx;
sz=sx;
if(hxPos>pPos){
[sx,sy,sz];
}else{[10,10,10]};Thanks for the response.
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the natural logarithmic function uses exponent integer e as its base value whose constant value is 2.718.
natural logarithmic functions are easily converted into its relative exponential functions as following:
log e y = x
to convert it into exponential form both RHS and LHS are put in exponent’s power as
e log e y = ex
we know that the exponents and logarithm are opposite to each other so
e cancels the log on LHS:
y = ex
‘e’ is also known as Euler Constant.
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