Master page having a vector mask layer

[HardyW]

How can I create on a master page a masking vector layer (ex. rounded rectangle) whose masked content is assigned when creating the pages?

When creating a masked layer and a vector object I can add the masked content on the page but afterwards I cannot modify the content anymore. If I just create a vector object on the master page, I cannot use it for masking on the pages.

Hardy

[Old Bruce]

Without knowing what it is you actually need I will say that you would most likely need to edit each Actual Page's Master Page as a Detached item in the layers panel.

Again not knowing what it is you are trying to achieve, I would suggest that perhaps a Picture frame would serve.

[thomaso]

You can place the masking object on the master and place all masked object on the document pages hierarchically below the master layer. This preserves direct access to the individual objects without the need to detach the master for object editing.

If you set the master layer's blend mode to "Erase" you can achieve transparency for the masking area, too:
(note, this blend mode causes rasterization on export)

Disadvantage: By default master layers are bottom layers in the Layers panel. Thus you need to move the master on the document pages.
This can be achieved with the master layer selected via:

• menu "Layer" > "Arrange" > "Move to Front"

• or the according Toolbar button: 

To move the master layer for all pages across the entire document select one of the master layers and choose "Detach Linked", then move as mentioned above.

BTW: You can not set the masking object directly on the Master Page to blend mode "Erase" because its blend mode will not affect layers outside its parent master layer on a document page and thus the masking object would not mask any more on a document page.

[HardyW]

Thanks Thomaso,

But I think that your solution is not working when the objects you want to mask are much larger than the masking layer, or?

I have attached a simple example showing what I want to achieve. In this case I have only created the final result on the page itself but not on the master page. I like to have the rounded rectangle (reality is more complex) on the master page. The masking layer should be placed on the master page. The to be masked objects should be individually added for each page using the particular master page.

 

Example.afpub

[thomaso]

1 hour ago, HardyW said:

But I think that your solution is not working when the objects you want to mask are much larger than the masking layer, or?

No, because also the mask is not limited in its size. It's masking rectangle can cover or exceed the full page + bleed, independent of the size of the object that causes the hole in the masking rectangle.

Alternative: If you want to mask on each page just 1 object which gets placed as resource, i.e. a file saved on disk + placed via "Place" command or "Place Image Tool", then using a Picture Frame as the masking object (mentioned before by @Old Bruce) may be simpler: It does not require the additional masking rectangle and offers its additional Picture Frame interface. You can turn any vector object into a Picture Frame.
• Advantage: This way the Master Layer doesn't need to be moved in the layer hierarchy on the document pages while the masked object would get placed inside the Picture Frame and thus inside the Master Layer on each document page.
• Unfortunately it does not work correctly if you populate the Picture Frame via copy/paste.

So it depends on your specific layout, the number and type of objects to be masked per page whether the Compound Mask or the Picture Frame method achieves the more efficient workflow.