understanding the simple deform modifier (TAPER - FACTOR) I'm trying to use the simple deform modifier to reproduce what the SHEAR operator does, in order to do so I'm using it in TAPER mode and locking one of the axis deformation, like that the object will deform correctly. My problem comes when I try to relate the angle deformation with the TAPER factor, with the SHEAR operator a value of 1 means the shear will be 45 degrees deformation but with the TAPER modifier I can't find the relation between angle and factor, somehow I think other variables are been considered as scale or object dimensions. Also the axis origin has an important role on how this modifier works.

So, can anyone offer a clear explanation on how this modifiers works?

Thanks
If you look at the source code of the simple deform modifier (1), the Taper transformation is done as follows. I assume that you selected the Z-axis as the deform axis.

scale = z * factor;
new_x = x + x * scale;
new_y = y + y * scale;
new_z = z;


So, every vertex of the object is scaled for the X and Y axis (unless, you have them locked). The z-coordinate remains untouched; maybe also the Y-coordinate, if you have locked it. You were right that the factor is mixed with other variables. As you can see, the factor is multiplied by the z coordinate. The further away a vertex is from the origin (as you suspected), the larger the scaling factor. At origin, z = 0, so the scaling is 0. At the top, z=1 (I assume!), so the scaling = factor. All vertices between origin and top are scaled between 0 and factor.

In the attached picture, I applied the taper modifier only to the group of top-right vertices. The origin of the cube is at the bottom. The factor is -1.000.

If the factor is -1.5, then

new_x = 1 + 1 * (1 * -1.5)= -0.5;


If you want the top-right vertices to collapse with the top-left vertices, the factor should be - 2; because

new_x = 1 + 1 * (1 * -2)= -1; 

which is the x-location of the top-left vertices.