scaling a mask, but not the image the mask is masking

[marc.cardwell]

hi, title clumsily says it all. i want to scale a circle vector mask, but not scale the image the circle vector mask is masking. i do see how to animate / move the mask Path, that's easy. a work-around (or maybe this is the bast way), is to and animate the Mask Expansion. what i'm needing to do looks like the image below. i tried editing Mask Shape, but figuring out what to enter for top, right, bottom, and left is more work than i want to learn how to do. thanks in advance for any help in this matter!

[Roei Tzoref · Accepted solution]

you can click twice on the mask or use the shortcut Ctrl+T - each will give you the transform box for the mask.

if you want more control, you might consider using a track matte (clipping mask) instead of a mask on the layer. simply create a shape layer or a masked solid above your source image and set the source to track matte the layer above like this:

now you can animate the matte freely from the shape instead of animating the path of the mask.

[marc.cardwell]

thank you! this is so easy, now i'm not sure what i was doing before. sometimes, when i double click, i get another window with that layer isolated. i need to click exactly on the mask path...

reading your second method (i remembered how to Toggle Switches, yea me), i think i can see what this is better, but i'll need to experiment more. i'm an old, long-time AI, PS and IND user, and i think in terms of the way these apps work. i love AE, but it often has its own way of doing things and it is a deep, dense app (which makes it so awesome).

[Roei Tzoref]

Yeah double clicking will get you sometimes so try Ctrl T instead. Also in the layer window is also a good and even superior way to manipulate your mask because you are in the layer context and not the composition. You even have quickmask mode

as for Ae's alpha matte - it's very similar to Ai's Clipping mask. The above layer is the matte (Mask) for the layer below.

[Rick Gerard]

The best way to edit mask or shape layer paths is to use the pen tool (g) and the Alt/Option and Ctrl/Cmnd modifier keys to cycle through the selection and modify tools. I rarely use the selection tool (v) to edit mask or even position paths. Here's what I mean: