Class Behavior
- Direct Known Subclasses:
Billboard
,Interpolator
,KeyNavigatorBehavior
,LOD
,Mouse6DPointerBehavior
,MouseBehavior
,PickMouseBehavior
,PickMouseBehavior
,PickMouseBehavior
,UnresolvedBehavior
,ViewPlatformBehavior
initialization
method, called once when the behavior
becomes "live," and a processStimulus
method called
whenever appropriate by the Java 3D behavior scheduler. The
Behavior node also contains an enable flag, a scheduling region,
a scheduling interval, and a wakeup condition.
The scheduling region defines a spatial volume that serves to enable the scheduling of Behavior nodes. A Behavior node is active (can receive stimuli) whenever an active ViewPlatform's activation volume intersects a Behavior object's scheduling region. Only active behaviors can receive stimuli.
The scheduling interval defines a partial order of execution for behaviors that wake up in response to the same wakeup condition (that is, those behaviors that are processed at the same "time"). Given a set of behaviors whose wakeup conditions are satisfied at the same time, the behavior scheduler will execute all behaviors in a lower scheduling interval before executing any behavior in a higher scheduling interval. Within a scheduling interval, behaviors can be executed in any order, or in parallel. Note that this partial ordering is only guaranteed for those behaviors that wake up at the same time in response to the same wakeup condition, for example, the set of behaviors that wake up every frame in response to a WakeupOnElapsedFrames(0) wakeup condition.
The initialize
method allows a Behavior object to
initialize its internal state and specify its initial wakeup
condition(s). Java 3D invokes a behavior's initialize code when the
behavior's containing BranchGroup node is added to the virtual
universe. Java 3D does not invoke the initialize method in a new
thread. Thus, for Java 3D to regain control, the initialize method
must not execute an infinite loop; it must return. Furthermore, a
wakeup condition must be set or else the behavior's processStimulus
method is never executed.
The processStimulus
method receives and processes a
behavior's ongoing messages. The Java 3D behavior scheduler invokes
a Behavior node's processStimulus method when an active ViewPlatform's
activation volume intersects a Behavior object's scheduling region
and all of that behavior's wakeup criteria are satisfied. The
processStimulus method performs its computations and actions
(possibly including the registration of state change information
that could cause Java 3D to wake other Behavior objects),
establishes its next wakeup condition, and finally exits.
A typical behavior will modify one or more nodes or node components
in the scene graph. These modifications can happen in parallel
with rendering. In general, applications cannot count on behavior
execution being synchronized with rendering. There are two
exceptions to this general rule:
- All modifications to scene graph objects (not including geometry
by-reference or texture by-reference) made from the
processStimulus
method of a single behavior instance are guaranteed to take effect in the same rendering frame. - All modifications to scene graph objects (not including geometry
by-reference or texture by-reference) made from the
processStimulus
methods of the set of behaviors that wake up in response to a WakeupOnElapsedFrames(0) wakeup condition are guaranteed to take effect in the same rendering frame.
Code Structure
When the Java 3D behavior scheduler invokes a Behavior object's processStimulus method, that method may perform any computation it wishes. Usually, it will change its internal state and specify its new wakeup conditions. Most probably, it will manipulate scene graph elements. However, the behavior code can only change those aspects of a scene graph element permitted by the capabilities associated with that scene graph element. A scene graph's capabilities restrict behavioral manipulation to those manipulations explicitly allowed.
The application must provide the Behavior object with references to those scene graph elements that the Behavior object will manipulate. The application provides those references as arguments to the behavior's constructor when it creates the Behavior object. Alternatively, the Behavior object itself can obtain access to the relevant scene graph elements either when Java 3D invokes its initialize method or each time Java 3D invokes its processStimulus method.
Behavior methods have a very rigid structure. Java 3D assumes that they always run to completion (if needed, they can spawn threads). Each method's basic structure consists of the following:
- Code to decode and extract references from the WakeupCondition enumeration that caused the object's awakening.
- Code to perform the manipulations associated with the WakeupCondition
- Code to establish this behavior's new WakeupCondition
- A path to Exit (so that execution returns to the Java 3D behavior scheduler)
WakeupCondition Object
A WakeupCondition object is an abstract class specialized to fourteen different WakeupCriterion objects and to four combining objects containing multiple WakeupCriterion objects. A Behavior node provides the Java 3D behavior scheduler with a WakeupCondition object. When that object's WakeupCondition has been satisfied, the behavior scheduler hands that same WakeupCondition back to the Behavior via an enumeration.
WakeupCriterion Object
Java 3D provides a rich set of wakeup criteria that Behavior objects can use in specifying a complex WakeupCondition. These wakeup criteria can cause Java 3D's behavior scheduler to invoke a behavior's processStimulus method whenever
- The center of a ViewPlatform enters a specified region
- The center of a ViewPlatform exits a specified region
- A behavior is activated
- A behavior is deactivated
- A specified TransformGroup node's transform changes
- Collision is detected between a specified Shape3D node's Geometry object and any other object
- Movement occurs between a specified Shape3D node's Geometry object and any other object with which it collides
- A specified Shape3D node's Geometry object no longer collides with any other object
- A specified Behavior object posts a specific event
- A specified AWT event occurs
- A specified time interval elapses
- A specified number of frames have been drawn
- The center of a specified Sensor enters a specified region
- The center of a specified Sensor exits a specified region
A Behavior object constructs a WakeupCriterion by constructing the appropriate criterion object. The Behavior object must provide the appropriate arguments (usually a reference to some scene graph object and possibly a region of interest). Thus, to specify a WakeupOnViewPlatformEntry, a behavior would specify the region that will cause the behavior to execute if an active ViewPlatform enters it.
Note that a unique WakeupCriterion object must be used with each instance of a Behavior. Sharing wakeup criteria among different instances of a Behavior is illegal.
Additional Information
For more information, see the Introduction to the Java 3D API and Behaviors and Interpolators documents.
- See Also:
-
Field Summary
Fields inherited from class javax.media.j3d.Node
ALLOW_AUTO_COMPUTE_BOUNDS_READ, ALLOW_AUTO_COMPUTE_BOUNDS_WRITE, ALLOW_BOUNDS_READ, ALLOW_BOUNDS_WRITE, ALLOW_COLLIDABLE_READ, ALLOW_COLLIDABLE_WRITE, ALLOW_LOCAL_TO_VWORLD_READ, ALLOW_LOCALE_READ, ALLOW_PARENT_READ, ALLOW_PICKABLE_READ, ALLOW_PICKABLE_WRITE, ENABLE_COLLISION_REPORTING, ENABLE_PICK_REPORTING
-
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionboolean
Retrieves the state of the Behavior enable flag.static int
Returns the number of scheduling intervals supported by this implementation of Java 3D.Retrieves the Behavior node's scheduling bounding leaf.Retrieves the Behavior node's scheduling bounds.int
Retrieves the current scheduling interval of this Behavior node.protected View
getView()
Returns the primary view associated with this behavior.protected WakeupCondition
Retrieves this behavior's current wakeup condition as set by the wakeupOn method.abstract void
Initialize this behavior.void
postId
(int postId) Posts the specified postId to the Behavior Scheduler.abstract void
processStimulus
(Enumeration criteria) Process a stimulus meant for this behavior.void
setEnable
(boolean state) Enables or disables this Behavior.void
Set the Behavior's scheduling region to the specified bounding leaf.void
setSchedulingBounds
(Bounds region) Set the Behavior's scheduling region to the specified bounds.void
setSchedulingInterval
(int schedulingInterval) Sets the scheduling interval of this Behavior node to the specified value.void
updateNodeReferences
(NodeReferenceTable referenceTable) Callback used to allow a node to check if any scene graph objects referenced by that node have been duplicated via a call tocloneTree
.protected void
wakeupOn
(WakeupCondition criteria) Defines this behavior's wakeup criteria.Methods inherited from class javax.media.j3d.Node
cloneNode, cloneTree, cloneTree, cloneTree, cloneTree, cloneTree, cloneTree, duplicateNode, getBounds, getBoundsAutoCompute, getCollidable, getLocale, getLocalToVworld, getLocalToVworld, getParent, getPickable, setBounds, setBoundsAutoCompute, setCollidable, setPickable
Methods inherited from class javax.media.j3d.SceneGraphObject
clearCapability, clearCapabilityIsFrequent, duplicateSceneGraphObject, getCapability, getCapabilityIsFrequent, getName, getUserData, isCompiled, isLive, setCapability, setCapabilityIsFrequent, setName, setUserData, toString
-
Constructor Details
-
Behavior
public Behavior()Constructs a Behavior node with default parameters. The default values are as follows:-
enable flag : true
scheduling bounds : null
scheduling bounding leaf : null
scheduling interval : numSchedulingIntervals / 2
-
-
Method Details
-
initialize
public abstract void initialize()Initialize this behavior. Classes that extend Behavior must provide their own initialize method.
NOTE: Applications should not call this method. It is called by the Java 3D behavior scheduler. -
processStimulus
Process a stimulus meant for this behavior. This method is invoked if the Behavior's wakeup criteria are satisfied and an active ViewPlatform's activation volume intersects with the Behavior's scheduling region. Classes that extend Behavior must provide their own processStimulus method.
NOTE: Applications should not call this method. It is called by the Java 3D behavior scheduler.- Parameters:
criteria
- an enumeration of triggered wakeup criteria for this behavior
-
setSchedulingBounds
Set the Behavior's scheduling region to the specified bounds. This is used when the scheduling bounding leaf is set to null.- Parameters:
region
- the bounds that contains the Behavior's new scheduling region
-
getSchedulingBounds
Retrieves the Behavior node's scheduling bounds.- Returns:
- this Behavior's scheduling bounds information
-
setSchedulingBoundingLeaf
Set the Behavior's scheduling region to the specified bounding leaf. When set to a value other than null, this overrides the scheduling bounds object.- Parameters:
region
- the bounding leaf node used to specify the Behavior node's new scheduling region
-
getSchedulingBoundingLeaf
Retrieves the Behavior node's scheduling bounding leaf.- Returns:
- this Behavior's scheduling bounding leaf information
-
wakeupOn
Defines this behavior's wakeup criteria. This method may only be called from a Behavior object's initialize or processStimulus methods to (re)arm the next wakeup. It should be the last thing done by those methods.- Parameters:
criteria
- the wakeup criteria for this behavior- Throws:
IllegalStateException
- if this method is called by a method other than initialize or processStimulus
-
getWakeupCondition
Retrieves this behavior's current wakeup condition as set by the wakeupOn method. If no wakeup condition is currently active, null will be returned. In particular, this means that null will be returned if Java 3D is executing this behavior's processStimulus routine and wakeupOn has not yet been called to re-arm the wakeup condition for next time.- Returns:
- the current wakeup condition for this behavior
- Since:
- Java 3D 1.3
-
postId
public void postId(int postId) Posts the specified postId to the Behavior Scheduler. All behaviors that have registered WakeupOnBehaviorPost with this postId, or a postId of 0, and with this behavior, or a null behavior, will have that wakeup condition met.This feature allows applications to send arbitrary events into the behavior scheduler stream. It can be used as a notification scheme for communicating events to behaviors in the system.
- Parameters:
postId
- the Id being posted- See Also:
-
setEnable
public void setEnable(boolean state) Enables or disables this Behavior. The default state is enabled.- Parameters:
state
- true or false to enable or disable this Behavior
-
getEnable
public boolean getEnable()Retrieves the state of the Behavior enable flag.- Returns:
- the Behavior enable state
-
getNumSchedulingIntervals
public static int getNumSchedulingIntervals()Returns the number of scheduling intervals supported by this implementation of Java 3D. The minimum number of supported intervals must be at least 10. The default scheduling interval for each behavior instance is set tonumSchedulingIntervals / 2
.- Returns:
- the number of supported scheduling intervals
- Since:
- Java 3D 1.3
-
setSchedulingInterval
public void setSchedulingInterval(int schedulingInterval) Sets the scheduling interval of this Behavior node to the specified value. The scheduling interval defines a partial order of execution for behaviors that wake up in response to the same wakeup condition (that is, those behaviors that are processed at the same "time"). Given a set of behaviors whose wakeup conditions are satisfied at the same time, the behavior scheduler will execute all behaviors in a lower scheduling interval before executing any behavior in a higher scheduling interval. Within a scheduling interval, behaviors can be executed in any order, or in parallel. Note that this partial ordering is only guaranteed for those behaviors that wake up at the same time in response to the same wakeup condition, for example, the set of behaviors that wake up every frame in response to a WakeupOnElapsedFrames(0) wakeup condition. The default value isnumSchedulingIntervals / 2
.- Parameters:
schedulingInterval
- the new scheduling interval- Throws:
IllegalArgumentException
- ifschedulingInterval
< 0 orschedulingInterval
>=numSchedulingIntervals
- Since:
- Java 3D 1.3
-
getSchedulingInterval
public int getSchedulingInterval()Retrieves the current scheduling interval of this Behavior node.- Returns:
- the current scheduling interval
- Since:
- Java 3D 1.3
-
getView
Returns the primary view associated with this behavior. This method is useful with certain types of behaviors (e.g., Billboard, LOD) that rely on per-View information and with behaviors in general in regards to scheduling (the distance from the view platform determines the active behaviors). The "primary" view is defined to be the first View attached to a live ViewPlatform, if there is more than one active View. So, for instance, Billboard behaviors would be oriented toward this primary view, in the case of multiple active views into the same scene graph. -
updateNodeReferences
Callback used to allow a node to check if any scene graph objects referenced by that node have been duplicated via a call tocloneTree
. This method is called bycloneTree
after all nodes in the sub-graph have been duplicated. The cloned Leaf node's method will be called and the Leaf node can then look up any object references by using thegetNewObjectReference
method found in theNodeReferenceTable
object. If a match is found, a reference to the corresponding object in the newly cloned sub-graph is returned. If no corresponding reference is found, either a DanglingReferenceException is thrown or a reference to the original object is returned depending on the value of theallowDanglingReferences
parameter passed in thecloneTree
call.NOTE: Applications should not call this method directly. It should only be called by the cloneTree method.
- Overrides:
updateNodeReferences
in classSceneGraphObject
- Parameters:
referenceTable
- a NodeReferenceTableObject that contains thegetNewObjectReference
method needed to search for new object instances.- See Also:
-