Damping a rapidly changing value

[Kevin Camp]

you could try smooth()…

try something like this:

br = thisComp.layer("White Solid 1").effect("CC Particle World")("Birth Rate"); //this is your particle system's birthrate
br.smooth(.2,5);

Kevin Camp
Senior Designer
KCPQ, KMYQ & KRCW

[Paul Roper]

Thanks for that Kevin. But, there a couple of things…
As you can see from the screenshot, no matter what values I put into the width and samples of the smooth function, there seems to be a very strange relationship between the input value and result. As I’ve highlighted, sometimes I get a complete inverse of the value.

Also, if I perform any mathematical operations on the variable before the smooth function, AE generates an error (br.smooth is undefined); ie:

br=thisComp.layer(“sparky 3”).effect(“CC Particle Systems II”)(“Birth Rate”);
br.smooth(.1,20)

…is fine, whereas:

br=thisComp.layer(“sparky 3”).effect(“CC Particle Systems II”)(“Birth Rate”)*18;
br.smooth(.1,20)

is not. I got around it by putting the *18 on an expression slider and passed that to the smooth function instead.

But the main issue is that I’d like to have the result spike nicely like the particle birth rate (ie. the light ‘cuts’ to full intensity) THEN fade off, rather than the smooth increase and decrease that the smooth function gives me. I think for now I’ll probably just manually keyframe it…but that’s always such a clunky way of doing things when I know I can get AE to do the work for me! But the only way I can think of doing it is by some elaborate if…then setup along the lines of:

if (birthrate at current time) is a lot more than (birthrate 1 frame ago) then
{
intensity = 900%
initiate some kind of Math.exp to fade it off
}
…or something along those lines.

Yeah….manual keyframing for now I think!

– Paul

[Mitch Mann]

I’d probably do a college-dropout method, something like this:

Get the value of the birth rate. Then get the value of the birthrate at a few places ahead in time and back in time (with valueAtTime.) Then use the highest value among these for your light. Or perhaps average all the values, depending on what you need / how it looks.