alternating rotation between position keyframes

[Frank Feijen]

Hi there,

I have a layers position keyframed, but now i’d like to add some degree of alternating random rotation.
for example:
at poskeyframe1 – rotation:+12
at poskeyframe2 – rotation:-20
at poskeyframe3 – rotation:+22
at poskeyframe4 – rotation:-6
…
I must admit not to have clue on how to do this. But since there will be tons of positionkeyframes, an expression would surely save my wrists.

[Dan Ebberts]

This might be close:

maxVal = 25;
minVal = 5;
n = 0;

if (position.numKeys > 0){
n = position.nearestKey(time).index;
if (position.key(n).time > time) n–;
}
if (n == 0){
seedRandom(1,true);
random(minVal,maxVal);
}else if (n == position.numKeys){
seedRandom(n,true);
a = random(minVal,maxVal);
if (n%2) a else -1;
}else{
seedRandom(n,true);
a1 = random(minVal,maxVal);
seedRandom(n+1,true);
a2 = random(minVal,maxVal);
if (n%2) a2 = -a2 else a1 = -a1;
t1 = position.key(n).time;
t2 = position.key(n+1).time;
linear(time,t1,t2,a1,a2);
}

Dan

[Frank Feijen]

Just 1 word for you: AWESOME!!

works perfect, thanks.