I would like to improve the documentation of the Simple Deform Modifier. Therefore, I have inspected the source code (click here to view online. The math is 'do-able'. For example: the transformation for the taper-mode is as follows. However, I have trouble understanding the coordinates
float x = r_co, y = r_co, z = r_co; float scale = z * factor; r_co = x + x * scale; r_co = y + y * scale; r_co = z;
I assume that the r_co to ... are the X,Y and Z-coordinates of the vertices. So, the tapering is scaled in the X and Y axes, with a weight from the Z-location/distance.
Is this Z-location/distance calculated from the origin of the mesh? It should be 0 at the origin because vertices are not scaled in X & Y axes for the origin-plane.
What is the Z-location/distance of a vertex at the border of the mesh? It should be 1 because the tapering is at its max at that point.
So, are these R_co ...  coordinates expressed in a number varying from -1 to +1, with 0 at the origin of the mesh? Is there any documentation about this?