Layer count

[Filip Vandueren]

Hi there,

it’s a property of Composition:

thisComp.numLayers

[Dmitry Kichenko]

Umph * shoots self *.

Why is it not docu… Wait, there it is in the helpfile.. Great..

Ok. I’ll be down at the local italian store buying loads of coffee.

Also, for future purposes, I would still like to know if there is a way to count objects of a particular kind (I don’t think they’re instanced from classes in JS unlike most OOP languages, and rather everything relies on inheritance, correct?).

[Dmitry Kichenko]

Thanks a lot! 🙂

[Filip Vandueren]

Indeed, in expressions there is no way to see all effects as lists, there are only functions to retrieve their value by index.
A possible hack could be this, for example to count the number of masks in layer 2:


countItems('thisComp.layer(2).mask');

function countItems(obj) {
a=0;
while (true) {
a++;
try {
eval(obj+"("+a+")");
}
catch(error) {
a--;
break;
}
}
return a
}

This constructs functions to loop through finding ‘child’ 1 to infinity, and as soon as we bump into an error, we know we’re one step to far: so a-1 = the number of children of the property

This should work with any layer or comp subobject, you can base the syntax of the string on what the pickwhip gives you.

For example, if you pickwhip to a an efects’ paramater, you can get something like:

thisComp.layer(“Black Solid 1”).effect(“Fast Blur”)(“Blurriness”)

If we want to know how manny effects that layer has, we need:

thisComp.layer(“Black Solid 1”).effect

how many parameters does fast blur have ?

thisComp.layer(“Black Solid 1”).effect(“Fast Blur”)

Yes: you can even count the number of parameters a subobject has, or the number of keyframes (though there is a numKeys property for that) see the marker example below:

examples:

countItems(“thisComp.layer”);
countItems(“thisComp.layer(1).effect”);
countItems(“thisComp.layer(1).effect(1).param”);

countItems(“thisComp.layer(1).mask”);
countItems(“thisComp.layer(1).mask(1).param”);

countItems(“thisComp.layer(1).transform”);
countItems(“thisComp.layer(2).marker.key”);
countItems(“thisComp.layer(2).motionTracker”);

sometimes you get unexpected numbers.. for example:

countItems(“thisComp.layer(2).text.animator(1).property”);

You’d expect to find how many properties are controlled by a certain text-animator (position, opacity,…) but you get “29”… no idea why.

countItems(“thisComp.layer(2).text.animator(1).selector”);
does return the exact number of selectors a textanimator has.

Anyway, I’m diving pretty deep under the hood here 😉

I wish AE had global functions, so you could put this function in a null somewhere and call it from whereever, but as it is right now, you have to include the entire function in every expression that needs to count.

[Dmitry Kichenko]

Thanks for the idea!

I actually built a pretty much the same loop on my own after not being able to locate a built-in function for that, but I didn’t know how to handle the error – as soon as the while loop encountered an object that didn’t exist (let’s say it was “white (thiscomp.layer(x)) where x was greater than the number of layers in the comp) it would spit out an error and not let me use the expression. The try-catch mechanism is quite clever. Haven’t dealt with it in other languages (mostly a PHP + ActionScript programmer here).

This is so much fun though, programming for graphics =). Forget keyframes! Thanks again!