start/stop expression at specific time

[Dan Ebberts]

I think it would look like this:


beginTime = 1;
endTime = 30;

yOrigin = 520;
seedRandom(index,true);
yDelta = random(-10,10);

f = timeToFrames(time);

if (f <= beginTime){
d = 0;
}else if (f <= endTime){
d = f - beginTime;
}else{
d = endTime - beginTime;
}
yNew = yOrigin + d*yDelta;
[value[0],yNew]


Although, if you wanted to key it to the layer’s in point, something like this might be better:


dur = 30;

yOrigin = 520;
seedRandom(index,true);
yDelta = random(-10,10);

f = Math.max(timeToFrames(time-inPoint),0);
d = (f < dur) ? f : dur;
yNew = yOrigin + d*yDelta;
[value[0],yNew]


Dan

[Cameron Walser]

Awesome thank you – one more quick question Dan –

1) How in the world do you have time to answer all these questions?!
🙂

[Dan Ebberts]

Sorry, no time to answer… 😉

[Cameron Walser]

Dan maybe you’ll know the answer to this one –
I’ve made a functional comp with the expression, finally, and the expression references Expression Sliders on a null layer. So after I duplicate the layer a thousand times, I can simply adjust the sliders on the one layer. Here’s the question – what if I want to change the expression itself? Do I have to re-duplicate the layer 1000 times? Or is there some way to reference a “Master” expression?

Latest expression posted just FYI

dur = 1;
x = thisComp.layer("NULL PARAMETERS").effect("X_Origin")("Slider");
f = (timeToFrames(time));
yOrigin = 500;
seedRandom(index,true);

y = linear(time, inPoint, inPoint + dur, thisComp.layer("NULL PARAMETERS").effect("Y_Origin")("Slider"), (thisComp.layer("NULL PARAMETERS").effect("Y_Origin")("Slider") - (random (thisComp.layer("NULL PARAMETERS").effect("Least")("Slider"), thisComp.layer("NULL PARAMETERS").effect("Most")("Slider")) ) ) );

[x, y]

[Dan Ebberts]

There are hacks for a master expression, like putting it in a hidden text layer, but it’s really inefficient. Faster than re-duplicating all the layers would be to change the expression in one layer, make sure that property is selected, Edit > Copy Expression Only, select all the other layers, Edit > Paste.

Dan

[David Chasterfield]

hello my friend 😉
i been trying to pick whip the position of layer A with layer B at second 2… so far i tried a few simple expressions coz I’m new at expressions but i failed , nothing worked for me… here one of them :

timeToStart=2;
if (time >=timeToStart)
{
thisComp.layer(“Shape Layer 1″).transform.position
}

as you can see there in the middle all i do is pick whip the position of the layer A to layer B , trying to get it to follow starting from second 2 …i tried this for the rotation and it did work , but for the position it gives me this error ” expression result must be of dimension 2 , not 1. “…
so if u can help or maybe write me an example i can work with , that would be really great , thanks in advance

[Dan Ebberts]

The expression needs to provide a legal position value before the start time. I’m not sure if this does what you want, but it should avoid the error:

timeToStart=2;
if (time >=timeToStart)
{
thisComp.layer(“Shape Layer 1”).transform.position
}else{
value
}

Dan

[David Chasterfield]

it did got rid of the error and it did what i wanted ^^
works like a charm ! thanks a lot my friend !

[David Chasterfield]

actually I’m having another problem now , it didn’t work with that shape layer because of the anchor point , so i used a null object and parented it to that shape layer and then used its position for the expression , but when second 2 comes the layer A the one i parented its position to the null’s , it don’t really follow it , it goes in some random position and it don’t even move lol , thought its parented !

[Dan Ebberts]

The new expression will probably need to look like this:

timeToStart=2;
if (time >=timeToStart)
{
thisComp.layer(“Null 1”).toComp([0,0,0])
}else{
value
}

Dan