In this tutorial, Tim Clapham from helloluxx.com takes you through the process of building a controller for a deformer object. In this example we take a null object and then use the position values to drive the strength of a bend deformer with a basic Xpresso setup.
Once this simple example is complete, the setup is enhanced by calculating the angle between the source object and the controller which is then used to drive the angle parameter in the bend deformer, thus the deformer always bends towards the controller.
This type of setup has many uses particularly for animation and the setup can easily be expanded upon to allow control of several deformers directly in the editor viewport. As an example, Tim takes the setup one stage further by adding the MoGraph Delay Effector into the equation. This allows you to add a spring effect or a nice ease into the deformer strength.