Certain visual objects change independent of user actions. For example, a clock in the virtual world should keep on ticking without user interaction. The clock is an example of animation. Animation could be defined as changes in the virtual universe that occur without direct user action
By contrast, changes in the virtual universe as a direct result of user actions are defined as interactions.
As with interaction, animations in Java 3D are implemented using Behavior objects
As you might imagine, any custom animation can be created using behavior objects. However, the Java 3D API provides a number of classes useful in creating animations without having to create a new class. It should come as no surprise that these classes are based on the Behavior class. One set of animation classes are known as interpolators. An Interpolator object, together with an Alpha object, manipulates some parameter of a scene graph object to create a time-based animation. The Alpha object provides the timing.