Can't apply expression to "Mask Shape"

[Disciple]

I just tried to apply an expression to mask shape, but it doesen't seem to want to allow me to. If I alt-click on the stopwatch nothing happens...

I also tried to make another parameter follow Mask Shape, but won't work either.

Alex

[Paul Tuersley]

Yeah that's right, you can't use Mask Shape with expressions. If you think
about it, it makes sense....most properties in AE are represented by 1-3
numeric values, but what values would you expect Mask Shape to return?
Mask Shape data is made up of any number of mask vertices, along with
their bezier handle information.

Having said that, it would be nice if we could at least use expressions on
Mask Shape in a very limited way. The only valid expressions I'd imagine
you'd be able to use would be to link one Mask Shape to another (creating
an exact copy of the source mask) along with being able to use the
'valueAtTime' option to offset the linked mask shape keyframes in time.

Paul T

[vaso]

Scripts let you assign the vertices to a mask - I'm trying to do it too, and I'm getting a help on it now, so if I learn how to do it, I'll share it with you. If you already know how to script, just have a look at the shape properties (look it up in the scripting reference pdf) and you're good to go. I personally just have to chew through some basics before I do it.

[Disciple]

I'm working on a script related to masks myself, as I need a script to add a specific mask to 40 or so layers in a comp.
I'm finding some useful information on Dan Ebberts site (Motionscript.com) about mask creation. Did you check it out?
Alex