Math.sin easing?

[Dan Ebberts]

Hard to guess what you’re after exactly, but maybe something like this:

freq = 2;
amp = 100;
period = 1/freq;
t = time%period;
tt = ease(t,0,period,0,period);
amp*Math.sin(freq*tt*Math.PI*2)

[Niek Pronk]

Hi Dan,

thank you so much for your reply. It’s not really doing what I wanted though.

Im trying to keep a pulse in my animation and let the Math.sin expression dictate that pulse. My expression is as follows:

x=value[0];

a=thisComp.layer(“SLIDER controls”).effect(“Amplitude 1”)(“Slider”);

f=1.8461538462;

t=time-inPoint;

y=Math.sin(t*2*Math.PI*f/thisComp.layer(“SLIDER controls”).effect(“Speed”)(“Slider”))*a;

[x,y]

It is generating a nice pulse (see my attached screenshot) but I would like the top and bottom half of the pulse to have more ease-in and ease-out. Is this possible?

Thanks again so much

Niek

[Filip Vandueren]

something like this:

s = Math.sin(t);
Math.pow(s, 0.5) * Math.sign(s);

as that 0.5 will tend to 0, the sin will flatten the tops and bottoms of the sinewave more and more, approaching a square wave. Making the value of the power larger than 1 will make it approach a ‘needle pulse’ as it tends to infinity.

If you are running the Legacy javascript engine. Math.sign() isnet supported and you would need this:

s = Math.sin(t);
Math.pow(s, 0.5) * (s<0 ? -1:1);

replace the “t” with your formula of course.

[Niek Pronk]

Hi Filip,

thanks a lot for your reply. Not sure if I am applying your suggestion correctly. Does it mean I paste your suggestion after I’ve defined y? Like this:

x=value[0];

a=thisComp.layer(“SLIDER controls”).effect(“Amplitude 1”)(“Slider”);

f=1.8461538462;

t=time-inPoint;

y=Math.sin(t*2*Math.PI*f/thisComp.layer(“SLIDER controls”).effect(“Speed”)(“Slider”))*a;

Math.pow(y, 0.5) * Math.sign(y);

[x,y]

Because that unfortunately doesn’t change the pulse of the math.sin. But maybe I am doing something wrong here..?

[Filip Vandueren]

You didn’t assign the new calculation to anything yet, so the y indeed stays unchanged.

The Math.pow should be done on a -1 to +1 sin value, so wait with mulitplying *a untill afterwards.

Like this:

y=Math.sin(t*2*Math.PI*f/thisComp.layer("SLIDER controls").effect("Speed")("Slider"));
y=Math.pow(y, 0.5) * Math.sign(y) * a;
[x,y]

[Niek Pronk]

Thanks for your help Filip. Unfortunately it’s giving me an error and the movement is somehow only going up..

[Filip Vandueren]

Can you tell me the error ?

Probably you are on an the legacy Javascript engine that doesn’t support Math.sign

replace it with (s<0 ? -1:1)

[Niek Pronk]

It is still only completing the top half of the pulse. AE tells me it cannot produce a numeric value for [x,y]

this is what i have now:

y=Math.sin(t*2*Math.PI*f/thisComp.layer(“SLIDER controls”).effect(“Speed”)(“Slider”));

y=Math.pow(y, 0.5) * (y<0 ? -1:1) * a;

[Filip Vandueren]

Sorry, i forgot to include Math.abs(y) inside the power !

x=value[0];
a=thisComp.layer("SLIDER controls").effect("Amplitude 1")("Slider");
f=1.8461538462;
t=time-inPoint;
y=Math.sin(t*2*Math.PI*f/thisComp.layer("SLIDER controls").effect("Speed")("Slider"));
y=Math.pow(Math.abs(y), 0.5) * Math.sign(y) * a;
[x,240+y];