javax.media.j3d
Class ViewPlatform

java.lang.Object
  extended by javax.media.j3d.SceneGraphObject
      extended by javax.media.j3d.Node
          extended by javax.media.j3d.Leaf
              extended by javax.media.j3d.ViewPlatform

public class ViewPlatform
extends Leaf

The ViewPlatform leaf node object controls the position, orientation and scale of the viewer. It is the node in the scene graph that a View object connects to. A viewer navigates through the virtual universe by changing the transform in the scene graph hierarchy above the ViewPlatform.

The View Attach Policy

The actual view that Java 3D's renderer draws depends on the view attach policy specified within the currently attached ViewPlatform. The view attach policy, set by the setViewAttachPolicy method, is one of the following:

Activation Radius

The ViewPlatform's activation radius defines an activation volume surrounding the center of the ViewPlatform. This activation volume is a spherical region that intersects with the scheduling regions and application regions of other leaf node objects to determine which of those objects may affect rendering. Only active view platforms--that is, view platforms attached to a View--will be used to schedule or select other leaf nodes.

Different leaf objects interact with the ViewPlatform's activation volume differently. The Background, Clip, and Soundscape leaf objects each define a set of attributes and an application region in which those attributes are applied. If more than one node of a given type (Background, Clip, or Soundscape) intersects an active ViewPlatform's activation volume, the "most appropriate" node is selected for that View. Sound leaf objects and Behavior objects become active when their scheduling region intersects an active ViewPlatform's activation volume.

The activation radius is in view platform coordinates. For the default screen scale policy of SCALE_SCREEN_SIZE, the activationRadius parameter value is multiplied by half the monitor screen size to derive the actual activation radius. For example, for the default screen size of 0.35 meters, and the default activation radius value of 62, the actual activation radius would be 10.85 meters.

See Also:
View

Field Summary
static int ALLOW_POLICY_READ
          Specifies that the ViewPlatform allows read access to its view attach policy information at runtime.
static int ALLOW_POLICY_WRITE
          Specifies that the ViewPlatform allows write access to its view attach policy information at runtime.
 
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
ViewPlatform()
          Constructs a ViewPlatform object with default parameters.
 
Method Summary
 Node cloneNode(boolean forceDuplicate)
          Used to create a new instance of the node.
 float getActivationRadius()
          Get the ViewPlatform's activation radius.
 int getViewAttachPolicy()
          Returns the current coexistence center in virtual-world policy.
 void setActivationRadius(float activationRadius)
          Set the ViewPlatform's activation radius which defines an activation volume around the view platform.
 void setViewAttachPolicy(int policy)
          Sets the view attach policy that determines the coexistence center in the virtual world.
 
Methods inherited from class javax.media.j3d.Node
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, updateNodeReferences
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Field Detail

ALLOW_POLICY_READ

public static final int ALLOW_POLICY_READ
Specifies that the ViewPlatform allows read access to its view attach policy information at runtime.

See Also:
Constant Field Values

ALLOW_POLICY_WRITE

public static final int ALLOW_POLICY_WRITE
Specifies that the ViewPlatform allows write access to its view attach policy information at runtime.

See Also:
Constant Field Values
Constructor Detail

ViewPlatform

public ViewPlatform()
Constructs a ViewPlatform object with default parameters. The default values are as follows:

Method Detail

setViewAttachPolicy

public void setViewAttachPolicy(int policy)
Sets the view attach policy that determines the coexistence center in the virtual world. This policy determines how Java 3D places the view platform relative to the position of the user's head, one of View.NOMINAL_SCREEN, View.NOMINAL_HEAD, or View.NOMINAL_FEET. The default policy is View.NOMINAL_HEAD.

Parameters:
policy - the new policy
Throws:
CapabilityNotSetException - if appropriate capability is not set and this object is part of live or compiled scene graph
See Also:
View.NOMINAL_SCREEN, View.NOMINAL_HEAD, View.NOMINAL_FEET

getViewAttachPolicy

public int getViewAttachPolicy()
Returns the current coexistence center in virtual-world policy.

Returns:
one of: View.NOMINAL_SCREEN, View.NOMINAL_HEAD, or View.NOMINAL_FEET
Throws:
CapabilityNotSetException - if appropriate capability is not set and this object is part of live or compiled scene graph

setActivationRadius

public void setActivationRadius(float activationRadius)
Set the ViewPlatform's activation radius which defines an activation volume around the view platform.

Parameters:
activationRadius - the new activation radius

getActivationRadius

public float getActivationRadius()
Get the ViewPlatform's activation radius.

Returns:
the ViewPlatform activation radius

cloneNode

public Node cloneNode(boolean forceDuplicate)
Used to create a new instance of the node. This routine is called by cloneTree to duplicate the current node. cloneNode should be overridden by any user subclassed objects. All subclasses must have their cloneNode method consist of the following lines:

     public Node cloneNode(boolean forceDuplicate) {
         UserSubClass usc = new UserSubClass();
         usc.duplicateNode(this, forceDuplicate);
         return usc;
     }
 

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


Copyright (c) 2006 Sun Microsystems, Inc. All rights reserved. Use is subject to license terms.