Is it possible to manipulate the individual vectors of a path or shape in After Effects using expressions?
No. The rest is far too vague to make any sense of it. There's a million ways to parametrically create shapes using combinations of effects, but you will have to be more clear about what you actuall want to do....
Okay, I'll be extremely specific, then.
I'm building a character's face in After Effects, using shapes, such as Ellipses, as the building blocks. However, if I want to convey a range of emotion, I need the shapes to be able to change dynamically.
I know its posible to alter the individual vectors of masks and shapes with the "tools". Can it be done with expressions? Could I, as an example, tell a specific vector on a mask or shape to move vertically by the amount of an expression control?
As I said, you can't. The question here is, whether you actually must animate the mask or shape layer paths? Most of that can be easily done with distortion effects (and much more intuitively, too) like Bezier Warp or the Puppet tool. So to me, you are simply following a wrong strategy here...
That's what I was looking for; I just wanted to know if it was possible or if I needed to be using a different technique. Thank you so much!
It is definitely possible to move the shapes around and modify their dimensions using expressions. With transform groups you can also modify the rotation. It works exactly the same as any other expressions -- each property that you want to modify has to have its own expression to calculate the final value for that property. The key is understanding how the groups and shapes relate to each other, and the best way to do that is to dive in and play around with them. Doing procedural facial animation this way would take some ingenuity to work out, but it can definitely be done. If you are just getting started with expressions, this might be a little ambitious as a first project, however.
Aaron is right, but I do have to reiterate this point (pun intended):
You can't manipulate individual points (vertices) of mask or shape paths with expressions. Scripts, yes; expressions, no.
I was looking for the same thing: I have a motion graphic that has a few circles connected by lines. In order to save some time I was considering using expressions to move a straight line end points (connecting one circle center to another).
Too bad this isn't possible, but is there any other way to make this easier than animating the shape by hand?
5 years later - - its possible now in cc2018
Create Nulls from Paths is how you would do it