user6123: Is it possible to create one mask or track matte mask on a parent null layer that applies to all child layers? Only way I've figured out is to apply a track matte to every layer I want masked which seems very inefficient. 
Cheers.


user6079: Like S-ed mentioned there are many ways.
I would Pre-compose all the layers I want masked. 
2 steps:
1) Select all layers you want masked, then click the menu item Layer -> Pre-Compose (or shift-command-C).
2) Then apply your mask to the Pre-comp that you just created. 
This keeps the workflow simple.
Keeping things simple would allow you to create more complex effects.
Good luck with your project.

user-1: Well, there a lot of ways to get result quicker, but each one depends on desirable result. =)
Here's one way:

Make desired null's mask
Make any mask for it's child (it doesn't matter what there)
Alt+click on child's mask path 'clock' icon (it'll open script settings)
Clear edit field or select all the contents
Drag 'link' icon (spiral) of mask path expression over Null's mask Path (it should add some kind of "thisComp.layer("Null 1").mask("Mask 1").maskPath" to expression field)
Copy this new mask to all childs

p.s.: this way is just a start, since it's not includes shifts of child and parent layers, but if pivots aligned it'll work

6123: <p>Is it possible to create one mask or track matte mask on a parent null layer that applies to all child layers? Only way I've figured out is to apply a track matte to every layer I want masked which seems very inefficient. </p>

<p>Cheers.</p>

<p><img src="https://i.stack.imgur.com/Y253B.png" alt="enter image description here"></p>
 6079: <p>Like S-ed mentioned there are many ways.</p>

<p>I would Pre-compose all the layers I want masked. 
2 steps:</p>

<p>1) Select all layers you want masked, then click the menu item Layer -> Pre-Compose (or shift-command-C).</p>

<p>2) Then apply your mask to the Pre-comp that you just created. </p>

<p>This keeps the workflow simple.
Keeping things simple would allow you to create more complex effects.</p>

<p>Good luck with your project.</p>
 -1: <p>Well, there a lot of ways to get result quicker, but each one depends on desirable result. =)</p>

<p>Here's one way:</p>

<ol>
<li>Make desired null's mask</li>
<li>Make any mask for it's child (it doesn't matter what there)</li>
<li>Alt+click on child's mask path 'clock' icon (it'll open script settings)</li>
<li>Clear edit field or select all the contents</li>
<li>Drag 'link' icon (spiral) of mask path expression over Null's mask Path (it should add some kind of "thisComp.layer("Null 1").mask("Mask 1").maskPath" to expression field)</li>
<li>Copy this new mask to all childs</li>
</ol>

<p>p.s.: this way is just a start, since it's not includes shifts of child and parent layers, but if pivots aligned it'll work</p>
