Well, all parallax is is this:
And the same with y
Z scaling is basically
X = f*originalx/z
Where f is the focal length. I don’t know what value construct uses for that.
There’s a bit more to it than that and usually they tie in the camera distance and relate it to the focal length. Also the perspective is around the center of the screen so we have:
X = cameraZ*(originalx-screenCenterX)/(z+cameraZ) + screenCenterX
Y is basically the same. Width and height are slightly simpler:
Width = cameraZ*originalWidth/(z+cameraZ)
As written, when the z of an object is unchanged then the position and size won’t change. Negative z is bigger and positive z is smaller. If that’s opposite then just make cameraZ negative. Smaller cameraZ values make more sever perspective and higher make less sever.
I haven’t investigated but cameraZ may be something simple like 500, or if C3 has a way to change it, then use that value.
Anyhoo I guess with all the above we can calculate the simulated z or scale of a certain parallax.
And looks like you assumption is correct. The scale is equal to the parallax.
On a side note if you wanted to do the parallax with z instead of a parallex layer you can do this:
Z = cameraZ/parallexX -cameraZ