Wow, James, way to knock the ball out of the park with that answer.
That was EXACTLY the correct way to do what the original questioner was looking for. For animating the mask on a non-transforming object inside a scene – basically keeping a tight roto around an object that isn’t moving – James’s explanation above is THE way to do it.
A great way to highlight an object in a scene.
A great way to blur a single object in a scene.
A great way to color correct an object, like a chair, in a scene.
So many uses. No need for scripts (because the original mask isn’t changing that much, just transforming along x and y.) Thanks James for setting it out step-by-like that.
Robert N.