7
Replies
Really...? I just can't imagine this to be the case, that would make the whole concept of expressions useless except for the most basic/trivial applications? If I were to apply a complex expression to a hundred layers or more, I would need to go back to all those layers in order to change anything? I want to use scripting to avoid that kind of manual nightmare...
This must be something to come up very often, maybe it's because I mainly do 3D animation where this sort of thing would be crazy 15 years ago let alone today. People actually write the same function inside each layer again and again..? It just goes against all my scripting sensibilities to accept that this is actually the case... 
Thanks for your reply anyway, it's very hard to wrap my mind around this workflow, the idea of creating a function and actually using it more than once is so incredibly basic it hurts my brain I can't do it in AE..
If you want to apply an expression to a bunch of layers you can use Edit>Copy Expression Only, then select all the layers and paste. You can also create an animation preset and apply that to as many layers as you want with one click. You can point a bunch of layers at controllers on a single layer. You can use the layer number or index to offset properties by different amounts. For example by applying an expression based on the position of layer 1 and adding the index value times 20 to the position of layer 2 will be offset 20 pixels. You can make expressions respond to the in and out points of a layer or make them do something based on a layer marker or a layer marker on another layer.
I'm not exactly sure what you are trying to do but if you want to have two nulls in your composition and 100 layers and then make the offset between each layer a percentage of the distance between the nulls so the layers fan out like a deck of playing cards this is entirely possible by defining the distance between the two nulls and then using the layer number to control the percentage. This way you can write one expression, copy it or make it an animation preset, then properly name your nulls, then select the 100 layers you want to distribute and apply your animation preset to the group. For example if I were to name my nulls L null and R null and want to distribute the layers in X between the two nulls starting at the right null the expression would look something like this:
L = thisComp.layer("L null").position;
R = thisComp.layer("R null").position;
C = [width/2, height/2];
len = length(L, R);
numl = thisComp.numLayers -2;
tl = index - 2;
ofst = 1/numl;
np = tl * (len * ofst);
[np, value[1]]
Just save this as an animation preset or apply it to the first layer in the timeline below the two nulls and copy the expression only and paste and you'll get something like this:
If you explain in detail what you are trying to do then maybe we can help....
Here is another approach to the problem of distributing a bunch of layers uniformly between two master layers. If you set up your composition with the top and bottom layers as controllers or nulls then this expression will distribute all layers in-between evenly between the controllers. You name the top and bottom controller "left" and "right" then add your in-between layers between them and apply the animation presets as needed.
l = thisComp.layer("left");
r = thisComp.layer("right");
thisLayer = index - l.index;
numLayer = r.index - l.index - 1;
if (numLayer <= 1){
ofst = (r.position - l.position)/2;
ofst + l.position
}
if (numLayer > 1) {
ofstMlt = 1/(numLayer -1);
ofst = (r.position - l.position) * ofstMlt;
ofstAdj = (ofst * thisLayer);
l.position + ofstAdj - ofst;
}
Here is how this works. The first two lines define the left and right layers as variables so we can extract their properties without a lot of typing. The third line extracts the adjusted layer number of the layers we are going to be distributing. The numLayer line extracts the number of layers between the "left" and "right" layers.
Now there's an if statement the corrects a divide by zero error if there is only one layer and centers that single layer between the "left" and "right" layer.
The next if statement sets up the position calculations for the distributed layers by first creating a multiplier so the distance between the controlling left and right layers can be evenly divided. For example, if you have 3 layers you'll want the first and third layer to be at the same position as the controllers and the middle layer to be half way between them so you divide 1 by one less than the total number of layers and end up with .5. Now it's a simple matter of subtracting the position of the left layer from the position of the right layer and multiplying it by .5
Here's the tricky part, you have to adjust the offset of the copies by multiplying the distributed layer's number by the layer number. In the three layer example the offset or distance between the first layer and the left controller would be the offset of the first layer multiplied by 1, the second layer would be the position of the would be the offset multiplied by 2 and the third would be the offset multiplied by 3.
The last finally positions the layer by starting with the "left" layer's position and adding the offset adjustment minus the offset to the position of the left controller.
This expression works with 2D and 3D layers and automatically evenly distributes as many layers as you like between your left and right controllers. Here's an animation preset you can use with CS6 or later: Dropbox - distribute left right.ffx
Here's what the composition looks like:
AdChoices