javax.media.j3d
Class Billboard

java.lang.Object
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  +--javax.media.j3d.SceneGraphObject
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        +--javax.media.j3d.Node
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              +--javax.media.j3d.Leaf
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                    +--javax.media.j3d.Behavior
                          |
                          +--javax.media.j3d.Billboard

public class Billboard

extends Behavior

The Billboard behavior node operates on the TransformGroup node to cause the local +z axis of the TransformGroup to point at the viewer's eye position. This is done regardless of the transforms above the specified TransformGroup node in the scene graph.

If the alignment mode is ROTATE_ABOUT_AXIS, the rotation will be around the specified axis. If the alignment mode is ROTATE_ABOUT_POINT, the rotation will be about the specified point, with an additional rotation to align the +y axis of the TransformGroup with the +y axis in the View.

Note that in a multiple View system, the alignment is done to the primary View only.

Billboard nodes are ideal for drawing screen aligned-text or for drawing roughly-symmetrical objects. A typical use might consist of a quadrilateral that contains a texture of a tree.

See Also:

OrientedShape3D

Field Summary

static int	ROTATE_ABOUT_AXIS Specifies that rotation should be about the specified axis.
static int	ROTATE_ABOUT_POINT Specifies that rotation should be about the specified point and that the children's Y-axis should match the view object's Y-axis.

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_PICKABLE_READ, ALLOW_PICKABLE_WRITE, ENABLE_COLLISION_REPORTING, ENABLE_PICK_REPORTING

Constructor Summary

Billboard()
Constructs a Billboard node with default parameters.

Billboard(TransformGroup tg)
Constructs a Billboard node with default parameters that operates on the specified TransformGroup node.

Billboard(TransformGroup tg, int mode, Point3f point)
Constructs a Billboard node with the specified rotation point and mode that operates on the specified TransformGroup node.

Billboard(TransformGroup tg, int mode, Vector3f axis)
Constructs a Billboard node with the specified axis and mode that operates on the specified TransformGroup node.

Method Summary

Node	cloneNode(boolean forceDuplicate) Creates a new instance of the node.
void	getAlignmentAxis(Vector3f axis) Gets the alignment axis and sets the parameter to this value.
int	getAlignmentMode() Gets the alignment mode.
void	getRotationPoint(Point3f point) Gets the rotation point and sets the parameter to this value.
TransformGroup	getTarget() Returns a copy of the transformGroup associated with this Billboard.
void	initialize() Initialize method that sets up initial wakeup criteria.
void	processStimulus(java.util.Enumeration criteria) Process stimulus method that computes appropriate transform.
void	setAlignmentAxis(float x, float y, float z) Sets the alignment axis.
void	setAlignmentAxis(Vector3f axis) Sets the alignment axis.
void	setAlignmentMode(int mode) Sets the alignment mode.
void	setRotationPoint(float x, float y, float z) Sets the rotation point.
void	setRotationPoint(Point3f point) Sets the rotation point.
void	setTarget(TransformGroup tg) Sets the tranformGroup for this Billboard object.
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 to cloneTree.

Methods inherited from class javax.media.j3d.Behavior

getEnable, getNumSchedulingIntervals, getSchedulingBoundingLeaf, getSchedulingBounds, getSchedulingInterval, getView, getWakeupCondition, postId, setEnable, setSchedulingBoundingLeaf, setSchedulingBounds, setSchedulingInterval, wakeupOn

Methods inherited from class javax.media.j3d.Node

cloneTree, cloneTree, cloneTree, cloneTree, cloneTree, cloneTree, duplicateNode, getBounds, getBoundsAutoCompute, getCollidable, getLocalToVworld, getLocalToVworld, getParent, getPickable, setBounds, setBoundsAutoCompute, setCollidable, setPickable

Methods inherited from class javax.media.j3d.SceneGraphObject

clearCapability, clearCapabilityIsFrequent, duplicateSceneGraphObject, getCapability, getCapabilityIsFrequent, getUserData, isCompiled, isLive, setCapability, setCapabilityIsFrequent, setUserData

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

ROTATE_ABOUT_AXIS

public static final int ROTATE_ABOUT_AXIS

Specifies that rotation should be about the specified axis.

See Also:

Constant Field Values

ROTATE_ABOUT_POINT

public static final int ROTATE_ABOUT_POINT

Specifies that rotation should be about the specified point and that the children's Y-axis should match the view object's Y-axis.

See Also:

Constant Field Values

Constructor Detail

Billboard

public Billboard()

Constructs a Billboard node with default parameters. The default values are as follows:

alignment mode : ROTATE_ABOUT_AXIS
alignment axis : Y-axis (0,1,0)
rotation point : (0,0,1)
target transform group: null

Billboard

public Billboard(TransformGroup tg)

Constructs a Billboard node with default parameters that operates on the specified TransformGroup node. The default alignment mode is ROTATE_ABOUT_AXIS rotation with the axis pointing along the Y axis.

Parameters:

tg - the TransformGroup node that this Billboard node operates upon

Billboard

public Billboard(TransformGroup tg,
                 int mode,
                 Vector3f axis)

Constructs a Billboard node with the specified axis and mode that operates on the specified TransformGroup node. The specified axis must not be parallel to the Z axis--(0,0,z) for any value of z. It is not possible for the +Z axis to point at the viewer's eye position by rotating about itself. The target transform will be set to the identity if the axis is (0,0,z).

Parameters:

tg - the TransformGroup node that this Billboard node operates upon

mode - alignment mode, one of ROTATE_ABOUT_AXIS or ROTATE_ABOUT_POINT

axis - the ray about which the billboard rotates

Billboard

public Billboard(TransformGroup tg,
                 int mode,
                 Point3f point)

Constructs a Billboard node with the specified rotation point and mode that operates on the specified TransformGroup node.

Parameters:

tg - the TransformGroup node that this Billboard node operates upon

mode - alignment mode, one of ROTATE_ABOUT_AXIS or ROTATE_ABOUT_POINT

point - the position about which the billboard rotates

Method Detail

setAlignmentMode

public void setAlignmentMode(int mode)

Sets the alignment mode.

Parameters:

mode - one of: ROTATE_ABOUT_AXIS or ROTATE_ABOUT_POINT

getAlignmentMode

public int getAlignmentMode()

Gets the alignment mode.

Returns:

one of: ROTATE_ABOUT_AXIS or ROTATE_ABOUT_POINT

setAlignmentAxis

public void setAlignmentAxis(Vector3f axis)

Sets the alignment axis. The specified axis must not be parallel to the Z axis--(0,0,z) for any value of z. It is not possible for the +Z axis to point at the viewer's eye position by rotating about itself. The target transform will be set to the identity if the axis is (0,0,z).

Parameters:

axis - the ray about which the billboard rotates

setAlignmentAxis

public void setAlignmentAxis(float x,
                             float y,
                             float z)

Sets the alignment axis. The specified axis must not be parallel to the Z axis--(0,0,z) for any value of z. It is not possible for the +Z axis to point at the viewer's eye position by rotating about itself. The target transform will be set to the identity if the axis is (0,0,z).

Parameters:

x - the x component of the ray about which the billboard rotates

y - the y component of the ray about which the billboard rotates

z - the z component of the ray about which the billboard rotates

getAlignmentAxis

public void getAlignmentAxis(Vector3f axis)

Gets the alignment axis and sets the parameter to this value.

Parameters:

axis - the vector that will contain the ray about which the billboard rotates

setRotationPoint

public void setRotationPoint(Point3f point)

Sets the rotation point.

Parameters:

point - the point about which the billboard rotates

setRotationPoint

public void setRotationPoint(float x,
                             float y,
                             float z)

Sets the rotation point.

Parameters:

x - the x component of the point about which the billboard rotates

y - the y component of the point about which the billboard rotates

z - the z component of the point about which the billboard rotates

getRotationPoint

public void getRotationPoint(Point3f point)

Gets the rotation point and sets the parameter to this value.

Parameters:

point - the position the Billboard rotates about

setTarget

public void setTarget(TransformGroup tg)

Sets the tranformGroup for this Billboard object.

Parameters:

tg - the transformGroup node which replaces the current transformGroup node for this Billboard

getTarget

public TransformGroup getTarget()

Returns a copy of the transformGroup associated with this Billboard.

Returns:

the TranformGroup for this Billboard

initialize

public void initialize()

Initialize method that sets up initial wakeup criteria.

Specified by:

initialize in class Behavior

processStimulus

public void processStimulus(java.util.Enumeration criteria)

Process stimulus method that computes appropriate transform.

Specified by:

processStimulus in class Behavior

Parameters:

criteria - an enumeration of the criteria that caused the stimulus

cloneNode

public Node cloneNode(boolean forceDuplicate)

Creates a new instance of the node. This routine is called by cloneTree to duplicate the current node.

Overrides:

cloneNode in class Node

Parameters:

forceDuplicate - when set to true, causes the duplicateOnCloneTree flag to be ignored. When false, the value of each node's duplicateOnCloneTree variable determines whether NodeComponent data is duplicated or copied.

See Also:

Node.cloneTree(), Node.cloneNode(boolean), Node.duplicateNode(javax.media.j3d.Node, boolean), NodeComponent.setDuplicateOnCloneTree(boolean)

updateNodeReferences

public 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 to cloneTree. This method is called by cloneTree 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 the getNewObjectReference method found in the NodeReferenceTable 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 the allowDanglingReferences parameter passed in the cloneTree call.

NOTE: Applications should not call this method directly. It should only be called by the cloneTree method.

Overrides:

updateNodeReferences in class Behavior

Parameters:

referenceTable - a NodeReferenceTableObject that contains the getNewObjectReference method needed to search for new object instances.

See Also:

NodeReferenceTable, Node.cloneTree(), DanglingReferenceException