When you first begin animating and working with keys, having Max figure out all the frames between the start and end keys seems amazing, especially if you've ever animated in 2D by drawing every frame. But soon you realize that animating with keys can be time-consuming for complex realistic motions, and again, Max comes to the rescue. You can use animation constraints and controllers to automate the creation of keys for certain types of motions.
Constraints and controllers store and manage the key values for all animations in Max. When you animate an object using the Auto Key button, the default controller is automatically assigned. You can change the assigned controller or alter its parameters using the Motion panel or the Track View.
This chapter explains how to work with constraints and some simple controllers. For example, you can use the Noise controller to add random motion to a flag blowing in the wind or use the Surface constraint to keep a bumper car moving over the surface.