Is there a way to transform the circle shape as a mask and its path as the mask path ?
not in a way that will do you any good (auto trace). what you could do instead is use a shape layer (bezier or parametric) and have a path and a lot of flexibility.
maybe you should specify what you want to accomplish and we can offer a few ways to get there
Thank you for your answer.
What I want to accomplish : a mask layer (shape circle) that move on a path (position : center of the circle, scale : radius of the circle).
What I have (mistakenly) done : the circle effet, and I have a lot of keyframes for position and radius.
I don't want to redo all teh work. Is there a solution make the circle acting as it is a mask ?
I have tried to make a shape layer (ellipse) as a mask. But I want to make that shape moving like the circle (position ands size)
Thanks again for the time spent to answer me.
Is there a solution make the circle acting as it is a mask ?
if you want to hide a layer there are other ways to accomplish it other than a mask on the layer. you can also use the Alpha Matte feature: set you "mask" layer on top of the layer it's suppose to obscure/reveal and set the below layer to use the upper as an Alpha matte. (think of it as the same as Illustrator clipping mask) more about it here: Luma and Alpha modes in track mattes | Adobe After Effects CC tutorials
have tried to make a shape layer (ellipse) as a mask. But I want to make that shape moving like the circle (position ands size)
you can use parenting to connect transform properties of scale,rotation and position of two layers or more. only transform: position,scale and rotation will be in a parent relationship - move the parent and the child will follow: https://helpx.adobe.com/after-effects/using/layer-properties.html#parent_and_child_layers
if this does not work for you try to visually show us how you want this to animate exactly.
Any luck on your issue?