Interaction - Interactive Web-Based Virtual Reality with Java 3D - page 166

Figure 6. WakeupCriterion and method

WakeupCriterion()
// Constructor for creating a WakeupCriterion object.

boolean hasTriggered()
// method returning a true if the specified criterion has given rise to the wakeup trigger.

Wakeup criterion Triggering event

WakeupOnActivation An object's scheduling region starts to intersect with the

ViewPlatform's activation volume

WakeupOnDeactivation An object's scheduling region no longer intersects with the

ViewPlatform's activation volume

WakeupOnAWTEvent A specific AWT event occurs

WakeupOnBehaviorPost A behavior object posts a specific event

WakeupOnCollisionEntry A specified object collides with other objects

WakeupOnCollisionExit A specified object no longer collides with other objects

WakeupOnCollisionMovement A specified object moves while colliding with other objects

WakeupOnElapsedFrames The elapsing of a specified number of frames

WakeupOnElapsedTime The elapsing of a specific number of milliseconds

WakeupOnSensorEntry A sensor has started to intersect a specified boundary

WakeupOnSensorExit The sensor no longer intersects the specified boundary

WakeupOnTransformChange The transform in a specified TransformGroup has changed

WakeupOnViewPlatformEntry The ViewPlatform's activation volume intersects with the specified

boundary

WakeupOnViewPlatformExit The ViewPlatform's activation volume no longer intersects the

specified boundary

A simple example illustrating the use of wakeup criterions is presented in Figure 7.
In this example, two wakeup criteria, WakeupOnActivation and WakeupOnDeactivation,
are used.
At the beginning, the bound region has a radius of 50 and the initial wakeup trigger
condition is set to correspond to that for WakeupOnActivation or when the ViewingPlatform
intersects the scheduling regions. Since the two regions do overlap at this time as illustrated,
the system will generate a trigger and control will be passed to the processStimulus method
to deal with this trigger.
In this simple example, the processStimulus method changes the scheduling region by
reducing its bound radius. As can be seen, the new scheduling region will not be intersecting