The 3D animation library supports two kinds of animations: synchronous and asynchronous ones.

An asynchronous animation is performed by attaching an {\em unsynchronized time-variant property value} pv to a geometric object go. Attaching pv to go immediately starts to animate go in some fashion, the animation ends once pv is again detached.

A synchronous animation, on the other hand, is performed by attaching a {\em synchronized time-variant property value} pv to a geometric object go, and then issuing an animation request to pv. Associated with each synchronous property value is an AnimHandle.T. However, pv will not immediately start to change.

The message ah.animate() will start to animate all time-varying property values tied to ah. The call to ah.animate() will return only after these animations are completed.

Animation handles are monitored: only one thread can call animate at any given time, and no thread can insert requests into the request queue of a synchronous property value while animate is in progress.

INTERFACE AnimHandle;

IMPORT ProxiedObj;

TYPE
  T <: Public;
  Public = ProxiedObj.T OBJECT
  METHODS
    init () : T;
    animate ();
  END;

ah.init() initializes a new animation handle ah and returns it. ah.animate() triggers the animation of all synchronous property values that are tied to ah. It returns when the animation is completed.

PROCEDURE New () : T;

New is a convenience procedure. The expression New() is equivalent to NEW(T).init()

END AnimHandle.