[Eduardo Oliveira]

Unfortunately at the moment after effects is unable to store variables. you can sample a value from the past, but not store values for posterior use ( the expression will re-run every frame, clearing any stored values again)
you can, however, use the key(n).time as a switch.. or the element position value as a threshold

[Eduardo Oliveira]

changing the “v” variable might give you wrong/weird results..

try changing the “parv” variable instead to below: ( although 20 is a bit overkill)

although in my opinion the best way to simulate wheight is the freq variable. heavier items should just have lower values.

i haven’t tested this tweak, se let me know if it works 🙂

parv=clamp(ppos.velocityAtTime(time- thisComp.frameDuration*20)[0]*amp,-90,90)

[Eduardo Oliveira]

Ps: the “serious math” wasn’t figured out by myself too 🙂
I took the famous Inertia bounce expression ( I think it was made by Dan Ebberts, orinally)
and just modified to suit your needs 🙂

Glad to be of help!

[Eduardo Oliveira]

forgot to say: you can adjust the parameteres to make small differences:
amp = this is how much of an overshoot will happen (higher = stronger)
freq= frequency of the swings ( higher = quicker swings)
and decay = how long before they come to a stop (higher = stops faster)

by tweaking those three you should be able to add enough variance.. also i made a slight tweak:
here is the revised one. let me know if it works well

//inertial children
n = 0;
amp = .04;
freq = 2.0;
decay = 3.0;

ppos=thisLayer.parent.transform.position;
parv=clamp(ppos.velocity[0]*amp,-90,90)
if (ppos.numKeys > 0){
n = ppos.nearestKey(time).index;
if (ppos.key(n).time > time){
n--;
}
}
if (n == 0){
ppos.velocity[0]
t = 100;
}else{
t = time - ppos.key(n).time;
}

if (n > 0){
v = ppos.velocityAtTime(ppos.key(n).time - thisComp.frameDuration/10)*-1;

parv + v[0]*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
parv
}

[Eduardo Oliveira]

with a little bit of manual work, you can do it.
first, move the controller null inside the comp with the solids.
now the manual labor part = relink the solids to the null inside the same comp

then duplicate the controller null onto the comp wich will be having the controllers.
make the original null(inside the comp with the solids) get all the relevant stuff from the one outside that comp.

now, when you duplicate the comp with the solids, all you have to do is change the target of the controlling null inside that comp….

sorry, i know that still involves a lot of manual changes – but at least if you need to replicate that a few times, it will save you some work

[Eduardo Oliveira]

i think i got something here:
i did it only considering lateral movement, so you wouldnt see any inertial rotation for y axis movements.
but it works well with dangling things…
here is the code:

//inertial children
n = 0;
amp = .04;
freq = 2.0;
decay = 3.0;

ppos=thisLayer.parent.transform.position;
parv=clamp(ppos.velocity[0]/10,-90,90)
if (ppos.numKeys > 0){
n = ppos.nearestKey(time).index;
if (ppos.key(n).time > time){
n--;
}
}
if (n == 0){
ppos.velocity[0]
t = 100;
}else{
t = time - ppos.key(n).time;
}

if (n > 0){
v = ppos.velocityAtTime(ppos.key(n).time - thisComp.frameDuration/10)*-1;

parv + v[0]*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
parv
}


[Eduardo Oliveira]

forgot to say – drop this in the “brightness” property of the optical flares layer

[Eduardo Oliveira]

hey, this seems to work:
change the “target” to your null
adjust the power variable to suit your needs.

target=thisComp.layer("Null 1");
power=10;
curv=target.transform.position[1];
oldv=target.transform.position.valueAtTime(time-0.1)[1];
v=oldv-curv;
v*power

[Eduardo Oliveira]

i really wish there was and EDIT button in this forum… hehehe.
anyways, probably very few people are even using these expressions, but after making a fool of myself twice, i realized that my fixes were false positives. anyways, i’ve spend a couple of hours, and i am almost sure that this time it works flawlessly. anyways, feel free to point out to me if it does not work for you.
as always, the expression goes in the “amount” field, not on the property used on the animator.

here it is:

//Inertia Bounce for TEXT per CHARACTER ANIMATION!

delay = .1;
tDelay = delay*textIndex;
n = 0;
if (numKeys > 0){
n = nearestKey(time-tDelay).index;
if (key(n).time > time-tDelay) n--;
}
if (n == 0){
t = 0;
}else{
t = time - key(n).time - tDelay;
}

if (n > 0){
v = velocityAtTime(key(n).time - thisComp.frameDuration/10);
amp = .05;
freq = 2.0;
decay = 2.0;
valueAtTime(time-tDelay) + v*amp*Math.sin(freq*t*2*Math.PI)/Math.exp(decay*t);
}else{
valueAtTime(time-tDelay);
}


[Eduardo Oliveira]

seems to me that if you just rename the layer “control green y” to “control green x” and delete the old one/rename it, then they would automatically point to the new one… am i wrong?