Animate a mask?

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samurle
Posts: 3
Joined: February 15th, 2010, 6:00 pm

February 16th, 2010, 6:37 pm

Is it possible to animate a mask path through an expression?
If so how?

In the Adobe docs, it says this:
Note: You can link Mask Path properties to other path properties (paths in a shape layer and brush strokes),
but the properties are not accessible for direct numerical manipulation through expressions.
I have a mask the shape of a simple rectangle, and I want to animate it based on some keyframe data in another layer.
Jorritschulte
Posts: 47
Joined: July 14th, 2008, 12:19 pm
Location: The Netherlands

February 25th, 2010, 4:19 am

You can't do this with mask Expressions.
i don't know what your project looks like, but you might just want to pickwhip the layer position to that keyframe data
samurle
Posts: 3
Joined: February 15th, 2010, 6:00 pm

February 25th, 2010, 2:18 pm

Jorritschulte wrote:You can't do this with mask Expressions.
i don't know what your project looks like, but you might just want to pickwhip the layer position to that keyframe data
Take this as an example:
On one layer, I have a bitmap, such as a large world map.
On the same layer, I have a small section that is masked out, only showing a portion of this map.
And I want to move the viewing area according to some keyframe data in some other layer.

So, if I move the layer position, I would be moving the entire layer (not the masked out portion).
Which wouldn't work. I hope that makes sense.

I suppose it's not possible for a mask to affect a layer that it doesn't belong to?
Paul Tuersley
Posts: 704
Joined: June 5th, 2004, 7:59 am
Location: London, UK

February 27th, 2010, 2:15 am

You could apply the mask to a solid layer placed above the map layer, then set the map layer to use the layer above as an alpha track matte. Then you can link the position of the solid to your keyframe data to get the solid layer / mask to move.
samurle
Posts: 3
Joined: February 15th, 2010, 6:00 pm

February 27th, 2010, 1:10 pm

Paul Tuersley wrote:You could apply the mask to a solid layer placed above the map layer, then set the map layer to use the layer above as an alpha track matte. Then you can link the position of the solid to your keyframe data to get the solid layer / mask to move.
Thanks for the suggestion. I've never used alpha track mattes before.
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