Expression that parents existing nulls to existing layers… maybe by #, in a loop, till all are parented?

[Dan Ebberts]

An expression can’t do that, but a script could. If you don’t care which null goes with which image, it might look like this:


var myComp = app.project.activeItem;
var myNulls = [];
var myImages = [];
var myLayer;

for (var i = 1; i <=myComp.numLayers; i++){
myLayer = myComp.layer(i);
if (myLayer.nullLayer && myLayer.threeDLayer){
myNulls.push(myLayer);
continue;
}
if ((myLayer instanceof AVLayer) && myLayer.threeDLayer && myLayer.source != null && myLayer.source.mainSource.isStill){
myImages.push(myLayer);
continue;
}
}

for (var i =0 ; i < Math.min(myNulls.length,myImages.length); i++){
myImages[i].parent = myNulls[i];
}


Dan

[James Poulakos]

Dan, thanks so much. That almost does the trick.

But the parented images don’t move to the positions of their parents. They just sit there, exactly where I placed them. They move in relation to the nulls, but I need each one to be relocated to its parent’s position in 3D space.

That’s normal parenting behavior. I need the parenting behavior you get when you hold down Shift while parenting. This snaps the child to the parent’s position.

Is there a way to modify the expression so that they get parented the same way that parenting works when I hold down Shift?

Or, if this is a quicker fix: I’m searching for a way to paste an expression on the child’s position that simply tells it: ‘make your position the same as your parent’ … but the methods I’m finding all seem to require an explicit reference to a parent, by its name. That won’t work. It would have to be “this layer’s parent, whatever that may be called”.

There’s gotta be a way to refer to a given layer’s parent, in expressions, without knowing in advance what the layer’s name is, right?

[Dan Ebberts]

You just need to add one line to the script, like this:


var myComp = app.project.activeItem;
var myNulls = [];
var myImages = [];
var myLayer;

for (var i = 1; i <=myComp.numLayers; i++){
myLayer = myComp.layer(i);
if (myLayer.nullLayer && myLayer.threeDLayer){
myNulls.push(myLayer);
continue;
}
if ((myLayer instanceof AVLayer) && myLayer.threeDLayer && myLayer.source != null && myLayer.source.mainSource.isStill){
myImages.push(myLayer);
continue;
}
}

for (var i =0 ; i < Math.min(myNulls.length,myImages.length); i++){
myImages[i].property("Position").setValue(myNulls[i].property("Position").value);
myImages[i].parent = myNulls[i];
}


You could instead add this expression:

[0,0,0];

To answer your other question, you can refer to layer’s parent like this:

parent.position

parent.rotation

etc.

Dan

[James Poulakos]

I think I just found a solution to the position problem: if I set the child’s position to 0,0,0 *but only after parenting it*, it jumps to the position of its parent.

I can change all of the children’s positions at once (thanks to After Effects’s brilliant keyboard shortcuts and its ability to edit a parameter on all selected objects at once).

Before I do any of this (running your script, editing their position), I must remember to set all image layers as 3D (duh) and set them to auto-orient to face the camera. If I leave the auto-orient step out till later, it won’t work, but if I apply it before I parent them, the orientation works.

[James Poulakos]

Whoops, I was writing my long post while you were posting your more elegant solution.

Wow, great to know that line about setting a layer’s position equal to another’s. Thanks again!