This Java tip illustrates the use of light scope groups in Java 3D scenes.

Three DirectionalLight nodes are added to illuminate a scene, selecting one of them to use at a time. Each light has a different scope group list, and thus illuminates different parts of the scene.

 import java.applet.Applet;
import java.awt.AWTEvent;
import java.awt.BorderLayout;
import java.awt.CheckboxMenuItem;
import java.awt.Component;
import java.awt.Cursor;
import java.awt.Frame;
import java.awt.Menu;
import java.awt.MenuBar;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.InputEvent;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.awt.event.MouseEvent;
import java.awt.event.WindowEvent;
import java.awt.event.WindowListener;
import java.io.File;
import java.util.Enumeration;
import java.util.EventListener;

import javax.media.j3d.AmbientLight;
import javax.media.j3d.Appearance;
import javax.media.j3d.Behavior;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.Canvas3D;
import javax.media.j3d.DirectionalLight;
import javax.media.j3d.Group;
import javax.media.j3d.Light;
import javax.media.j3d.Material;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.media.j3d.WakeupCriterion;
import javax.media.j3d.WakeupOnAWTEvent;
import javax.media.j3d.WakeupOnElapsedFrames;
import javax.media.j3d.WakeupOr;
import javax.vecmath.Color3f;
import javax.vecmath.Matrix4d;
import javax.vecmath.Point3d;
import javax.vecmath.Point3f;
import javax.vecmath.Vector3d;
import javax.vecmath.Vector3f;

import com.sun.j3d.utils.geometry.Primitive;
import com.sun.j3d.utils.geometry.Sphere;
import com.sun.j3d.utils.universe.PlatformGeometry;
import com.sun.j3d.utils.universe.SimpleUniverse;
import com.sun.j3d.utils.universe.Viewer;
import com.sun.j3d.utils.universe.ViewingPlatform;

public class ExLightScope extends Java3DFrame {
  //--------------------------------------------------------------
  //  SCENE CONTENT
  //--------------------------------------------------------------

  //
  //  Nodes (updated via menu)
  //
  private DirectionalLight light1 = null;

  private DirectionalLight light2 = null;

  private DirectionalLight light3 = null;

  private Group content1 = null;

  private Group content2 = null;

  //
  //  Build scene
  //
  public Group buildScene() {
    // Turn off the example headlight
    setHeadlightEnable(false);

    // Build the scene group
    Group scene = new Group();

    // Build foreground geometry into two groups. We'll
    // create three directional lights below, one each with
    // scope to cover the first geometry group only, the
    // second geometry group only, or both geometry groups.
    content1 = new SphereGroup(0.25f, // radius of spheres
        1.5f, // x spacing
        0.75f, // y spacing
        3, // number of spheres in X
        5, // number of spheres in Y
        null); // appearance
    scene.addChild(content1);

    content2 = new SphereGroup(0.25f, // radius of spheres
        1.5f, // x spacing
        0.75f, // y spacing
        2, // number of spheres in X
        5, // number of spheres in Y
        null); // appearance
    scene.addChild(content2);

    // BEGIN EXAMPLE TOPIC
    // Create influencing bounds
    BoundingSphere worldBounds = new BoundingSphere(new Point3d(0.0, 0.0,
        0.0), // Center
        1000.0); // Extent

    // Add three directional lights whose scopes are set
    // to cover one, the other, or both of the shape groups
    // above. Also set the lights' color and aim direction.

    // Light #1 with content1 scope
    light1 = new DirectionalLight();
    light1.setEnable(light1OnOff);
    light1.setColor(Red);
    light1.setDirection(new Vector3f(1.0f, 0.0f, -1.0f));
    light1.setInfluencingBounds(worldBounds);
    light1.addScope(content1);
    light1.setCapability(Light.ALLOW_STATE_WRITE);
    scene.addChild(light1);

    // Light #2 with content2 scope
    light2 = new DirectionalLight();
    light2.setEnable(light2OnOff);
    light2.setColor(Blue);
    light2.setDirection(new Vector3f(1.0f, 0.0f, -1.0f));
    light2.setInfluencingBounds(worldBounds);
    light2.addScope(content2);
    light2.setCapability(Light.ALLOW_STATE_WRITE);
    scene.addChild(light2);

    // Light #3 with universal scope (the default)
    light3 = new DirectionalLight();
    light3.setEnable(light3OnOff);
    light3.setColor(White);
    light3.setDirection(new Vector3f(1.0f, 0.0f, -1.0f));
    light3.setInfluencingBounds(worldBounds);
    light3.setCapability(Light.ALLOW_STATE_WRITE);
    scene.addChild(light3);

    // Add an ambient light to dimly illuminate the rest of
    // the shapes in the scene to help illustrate that the
    // directional lights are being scoped... otherwise it looks
    // like we're just removing shapes from the scene
    AmbientLight ambient = new AmbientLight();
    ambient.setEnable(true);
    ambient.setColor(White);
    ambient.setInfluencingBounds(worldBounds);
    scene.addChild(ambient);
    // END EXAMPLE TOPIC

    return scene;
  }

  //--------------------------------------------------------------
  //  USER INTERFACE
  //--------------------------------------------------------------

  //
  //  Main
  //
  public static void main(String[] args) {
    ExLightScope ex = new ExLightScope();
    ex.initialize(args);
    ex.buildUniverse();
    ex.showFrame();
  }

  //  Menu choices
  private boolean light1OnOff = true;

  private CheckboxMenuItem light1OnOffMenu;

  private boolean light2OnOff = true;

  private CheckboxMenuItem light2OnOffMenu;

  private boolean light3OnOff = false;

  private CheckboxMenuItem light3OnOffMenu;

  //
  //  Initialize the GUI (application and applet)
  //
  public void initialize(String[] args) {
    // Initialize the window, menubar, etc.
    super.initialize(args);
    exampleFrame.setTitle("Java 3D Light Scoping Example");

    //
    //  Add a menubar menu to change node parameters
    //    Use bounding leaf
    //

    Menu m = new Menu("DirectionalLights");

    light1OnOffMenu = new CheckboxMenuItem(
        "Red light with sphere set 1 scope", light1OnOff);
    light1OnOffMenu.addItemListener(this);
    m.add(light1OnOffMenu);

    light2OnOffMenu = new CheckboxMenuItem(
        "Blue light with sphere set 2 scope", light2OnOff);
    light2OnOffMenu.addItemListener(this);
    m.add(light2OnOffMenu);

    light3OnOffMenu = new CheckboxMenuItem(
        "White light with universal scope", light3OnOff);
    light3OnOffMenu.addItemListener(this);
    m.add(light3OnOffMenu);

    exampleMenuBar.add(m);
  }

  //
  //  Handle checkboxes and menu choices
  //
  public void itemStateChanged(ItemEvent event) {
    Object src = event.getSource();
    if (src == light1OnOffMenu) {
      light1OnOff = light1OnOffMenu.getState();
      light1.setEnable(light1OnOff);
      return;
    }
    if (src == light2OnOffMenu) {
      light2OnOff = light2OnOffMenu.getState();
      light2.setEnable(light2OnOff);
      return;
    }
    if (src == light3OnOffMenu) {
      light3OnOff = light3OnOffMenu.getState();
      light3.setEnable(light3OnOff);
      return;
    }

    // Handle all other checkboxes
    super.itemStateChanged(event);
  }
}

//
//CLASS
//SphereGroup - create a group of spheres on the XY plane
//
//DESCRIPTION
//An XY grid of spheres is created. The number of spheres in X and Y,
//the spacing in X and Y, the sphere radius, and the appearance can
//all be set.
//
//This grid of spheres is used by several of the examples as a generic
//bit of foreground geometry.
//
//SEE ALSO
//Ex*Light
//ExBackground*
//
//AUTHOR
//David R. Nadeau / San Diego Supercomputer Center
//

class SphereGroup extends Group {
  //  Constructors
  public SphereGroup() {
    //    radius x,y spacing x,y count appearance
    this(0.25f, 0.75f, 0.75f, 5, 5, null);
  }

  public SphereGroup(Appearance app) {
    //    radius x,y spacing x,y count appearance
    this(0.25f, 0.75f, 0.75f, 5, 5, app);
  }

  public SphereGroup(float radius, float xSpacing, float ySpacing,
      int xCount, int yCount) {
    this(radius, xSpacing, ySpacing, xCount, yCount, null);
  }

  public SphereGroup(float radius, float xSpacing, float ySpacing,
      int xCount, int yCount, Appearance app) {
    if (app == null) {
      app = new Appearance();
      Material material = new Material();
      material.setDiffuseColor(new Color3f(0.8f, 0.8f, 0.8f));
      material.setSpecularColor(new Color3f(0.0f, 0.0f, 0.0f));
      material.setShininess(0.0f);
      app.setMaterial(material);
    }

    double xStart = -xSpacing * (double) (xCount - 1) / 2.0;
    double yStart = -ySpacing * (double) (yCount - 1) / 2.0;

    Sphere sphere = null;
    TransformGroup trans = null;
    Transform3D t3d = new Transform3D();
    Vector3d vec = new Vector3d();
    double x, y = yStart, z = 0.0;
    for (int i = 0; i < yCount; i++) {
      x = xStart;
      for (int j = 0; j < xCount; j++) {
        vec.set(x, y, z);
        t3d.setTranslation(vec);
        trans = new TransformGroup(t3d);
        addChild(trans);

        sphere = new Sphere(radius, // sphere radius
            Primitive.GENERATE_NORMALS, // generate normals
            16, // 16 divisions radially
            app); // it's appearance
        trans.addChild(sphere);
        x += xSpacing;
      }
      y += ySpacing;
    }
  }
}

/**
 * The Example class is a base class extended by example applications. The class
 * provides basic features to create a top-level frame, add a menubar and
 * Canvas3D, build the universe, set up "examine" and "walk" style navigation
 * behaviors, and provide hooks so that subclasses can add 3D content to the
 * example's universe.
 * <P>
 * Using this Example class simplifies the construction of example applications,
 * enabling the author to focus upon 3D content and not the busywork of creating
 * windows, menus, and universes.
 * 
 * @version 1.0, 98/04/16
 * @author David R. Nadeau, San Diego Supercomputer Center
 */

class Java3DFrame extends Applet implements WindowListener, ActionListener,
    ItemListener, CheckboxMenuListener {
  //  Navigation types
  public final static int Walk = 0;

  public final static int Examine = 1;

  //  Should the scene be compiled?
  private boolean shouldCompile = true;

  //  GUI objects for our subclasses
  protected Java3DFrame example = null;

  protected Frame exampleFrame = null;

  protected MenuBar exampleMenuBar = null;

  protected Canvas3D exampleCanvas = null;

  protected TransformGroup exampleViewTransform = null;

  protected TransformGroup exampleSceneTransform = null;

  protected boolean debug = false;

  //  Private GUI objects and state
  private boolean headlightOnOff = true;

  private int navigationType = Examine;

  private CheckboxMenuItem headlightMenuItem = null;

  private CheckboxMenuItem walkMenuItem = null;

  private CheckboxMenuItem examineMenuItem = null;

  private DirectionalLight headlight = null;

  private ExamineViewerBehavior examineBehavior = null;

  private WalkViewerBehavior walkBehavior = null;

  //--------------------------------------------------------------
  //  ADMINISTRATION
  //--------------------------------------------------------------

  /**
   * The main program entry point when invoked as an application. Each example
   * application that extends this class must define their own main.
   * 
   * @param args
   *            a String array of command-line arguments
   */
  public static void main(String[] args) {
    Java3DFrame ex = new Java3DFrame();
    ex.initialize(args);
    ex.buildUniverse();
    ex.showFrame();
  }

  /**
   * Constructs a new Example object.
   * 
   * @return a new Example that draws no 3D content
   */
  public Java3DFrame() {
    // Do nothing
  }

  /**
   * Initializes the application when invoked as an applet.
   */
  public void init() {
    // Collect properties into String array
    String[] args = new String[2];
    // NOTE: to be done still...

    this.initialize(args);
    this.buildUniverse();
    this.showFrame();

    // NOTE: add something to the browser page?
  }

  /**
   * Initializes the Example by parsing command-line arguments, building an
   * AWT Frame, constructing a menubar, and creating the 3D canvas.
   * 
   * @param args
   *            a String array of command-line arguments
   */
  protected void initialize(String[] args) {
    example = this;

    // Parse incoming arguments
    parseArgs(args);

    // Build the frame
    if (debug)
      System.err.println("Building GUI...");
    exampleFrame = new Frame();
    exampleFrame.setSize(640, 480);
    exampleFrame.setTitle("Java 3D Example");
    exampleFrame.setLayout(new BorderLayout());

    // Set up a close behavior
    exampleFrame.addWindowListener(this);

    // Create a canvas
    exampleCanvas = new Canvas3D(null);
    exampleCanvas.setSize(630, 460);
    exampleFrame.add("Center", exampleCanvas);

    // Build the menubar
    exampleMenuBar = this.buildMenuBar();
    exampleFrame.setMenuBar(exampleMenuBar);

    // Pack
    exampleFrame.pack();
    exampleFrame.validate();
    //    exampleFrame.setVisible( true );
  }

  /**
   * Parses incoming command-line arguments. Applications that subclass this
   * class may override this method to support their own command-line
   * arguments.
   * 
   * @param args
   *            a String array of command-line arguments
   */
  protected void parseArgs(String[] args) {
    for (int i = 0; i < args.length; i++) {
      if (args[i].equals("-d"))
        debug = true;
    }
  }

  //--------------------------------------------------------------
  //  SCENE CONTENT
  //--------------------------------------------------------------

  /**
   * Builds the 3D universe by constructing a virtual universe (via
   * SimpleUniverse), a view platform (via SimpleUniverse), and a view (via
   * SimpleUniverse). A headlight is added and a set of behaviors initialized
   * to handle navigation types.
   */
  protected void buildUniverse() {
    //
    //  Create a SimpleUniverse object, which builds:
    //
    //    - a Locale using the given hi-res coordinate origin
    //
    //    - a ViewingPlatform which in turn builds:
    //          - a MultiTransformGroup with which to move the
    //            the ViewPlatform about
    //
    //          - a ViewPlatform to hold the view
    //
    //          - a BranchGroup to hold avatar geometry (if any)
    //
    //          - a BranchGroup to hold view platform
    //            geometry (if any)
    //
    //    - a Viewer which in turn builds:
    //          - a PhysicalBody which characterizes the user's
    //            viewing preferences and abilities
    //
    //          - a PhysicalEnvironment which characterizes the
    //            user's rendering hardware and software
    //
    //          - a JavaSoundMixer which initializes sound
    //            support within the 3D environment
    //
    //          - a View which renders the scene into a Canvas3D
    //
    //  All of these actions could be done explicitly, but
    //  using the SimpleUniverse utilities simplifies the code.
    //
    if (debug)
      System.err.println("Building scene graph...");
    SimpleUniverse universe = new SimpleUniverse(null, // Hi-res coordinate
        // for the origin -
        // use default
        1, // Number of transforms in MultiTransformGroup
        exampleCanvas, // Canvas3D into which to draw
        null); // URL for user configuration file - use defaults

    //
    //  Get the viewer and create an audio device so that
    //  sound will be enabled in this content.
    //
    Viewer viewer = universe.getViewer();
    viewer.createAudioDevice();

    //
    //  Get the viewing platform created by SimpleUniverse.
    //  From that platform, get the inner-most TransformGroup
    //  in the MultiTransformGroup. That inner-most group
    //  contains the ViewPlatform. It is this inner-most
    //  TransformGroup we need in order to:
    //
    //    - add a "headlight" that always aims forward from
    //       the viewer
    //
    //    - change the viewing direction in a "walk" style
    //
    //  The inner-most TransformGroup's transform will be
    //  changed by the walk behavior (when enabled).
    //
    ViewingPlatform viewingPlatform = universe.getViewingPlatform();
    exampleViewTransform = viewingPlatform.getViewPlatformTransform();

    //
    //  Create a "headlight" as a forward-facing directional light.
    //  Set the light's bounds to huge. Since we want the light
    //  on the viewer's "head", we need the light within the
    //  TransformGroup containing the ViewPlatform. The
    //  ViewingPlatform class creates a handy hook to do this
    //  called "platform geometry". The PlatformGeometry class is
    //  subclassed off of BranchGroup, and is intended to contain
    //  a description of the 3D platform itself... PLUS a headlight!
    //  So, to add the headlight, create a new PlatformGeometry group,
    //  add the light to it, then add that platform geometry to the
    //  ViewingPlatform.
    //
    BoundingSphere allBounds = new BoundingSphere(
        new Point3d(0.0, 0.0, 0.0), 100000.0);

    PlatformGeometry pg = new PlatformGeometry();
    headlight = new DirectionalLight();
    headlight.setColor(White);
    headlight.setDirection(new Vector3f(0.0f, 0.0f, -1.0f));
    headlight.setInfluencingBounds(allBounds);
    headlight.setCapability(Light.ALLOW_STATE_WRITE);
    pg.addChild(headlight);
    viewingPlatform.setPlatformGeometry(pg);

    //
    //  Create the 3D content BranchGroup, containing:
    //
    //    - a TransformGroup who's transform the examine behavior
    //      will change (when enabled).
    //
    //    - 3D geometry to view
    //
    // Build the scene root
    BranchGroup sceneRoot = new BranchGroup();

    // Build a transform that we can modify
    exampleSceneTransform = new TransformGroup();
    exampleSceneTransform
        .setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
    exampleSceneTransform
        .setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
    exampleSceneTransform.setCapability(Group.ALLOW_CHILDREN_EXTEND);

    //
    //  Build the scene, add it to the transform, and add
    //  the transform to the scene root
    //
    if (debug)
      System.err.println("  scene...");
    Group scene = this.buildScene();
    exampleSceneTransform.addChild(scene);
    sceneRoot.addChild(exampleSceneTransform);

    //
    //  Create a pair of behaviors to implement two navigation
    //  types:
    //
    //    - "examine": a style where mouse drags rotate about
    //      the scene's origin as if it is an object under
    //      examination. This is similar to the "Examine"
    //      navigation type used by VRML browsers.
    //
    //    - "walk": a style where mouse drags rotate about
    //      the viewer's center as if the viewer is turning
    //      about to look at a scene they are in. This is
    //      similar to the "Walk" navigation type used by
    //      VRML browsers.
    //
    //  Aim the examine behavior at the scene's TransformGroup
    //  and add the behavior to the scene root.
    //
    //  Aim the walk behavior at the viewing platform's
    //  TransformGroup and add the behavior to the scene root.
    //
    //  Enable one (and only one!) of the two behaviors
    //  depending upon the current navigation type.
    //
    examineBehavior = new ExamineViewerBehavior(exampleSceneTransform, // Transform
        // gorup
        // to
        // modify
        exampleFrame); // Parent frame for cusor changes
    examineBehavior.setSchedulingBounds(allBounds);
    sceneRoot.addChild(examineBehavior);

    walkBehavior = new WalkViewerBehavior(exampleViewTransform, // Transform
        // group to
        // modify
        exampleFrame); // Parent frame for cusor changes
    walkBehavior.setSchedulingBounds(allBounds);
    sceneRoot.addChild(walkBehavior);

    if (navigationType == Walk) {
      examineBehavior.setEnable(false);
      walkBehavior.setEnable(true);
    } else {
      examineBehavior.setEnable(true);
      walkBehavior.setEnable(false);
    }

    //
    //  Compile the scene branch group and add it to the
    //  SimpleUniverse.
    //
    if (shouldCompile)
      sceneRoot.compile();
    universe.addBranchGraph(sceneRoot);

    reset();
  }

  /**
   * Builds the scene. Example application subclasses should replace this
   * method with their own method to build 3D content.
   * 
   * @return a Group containing 3D content to display
   */
  public Group buildScene() {
    // Build the scene group containing nothing
    Group scene = new Group();
    return scene;
  }

  //--------------------------------------------------------------
  //  SET/GET METHODS
  //--------------------------------------------------------------

  /**
   * Sets the headlight on/off state. The headlight faces forward in the
   * direction the viewer is facing. Example applications that add their own
   * lights will typically turn the headlight off. A standard menu item
   * enables the headlight to be turned on and off via user control.
   * 
   * @param onOff
   *            a boolean turning the light on (true) or off (false)
   */
  public void setHeadlightEnable(boolean onOff) {
    headlightOnOff = onOff;
    if (headlight != null)
      headlight.setEnable(headlightOnOff);
    if (headlightMenuItem != null)
      headlightMenuItem.setState(headlightOnOff);
  }

  /**
   * Gets the headlight on/off state.
   * 
   * @return a boolean indicating if the headlight is on or off
   */
  public boolean getHeadlightEnable() {
    return headlightOnOff;
  }

  /**
   * Sets the navigation type to be either Examine or Walk. The Examine
   * navigation type sets up behaviors that use mouse drags to rotate and
   * translate scene content as if it is an object held at arm's length and
   * under examination. The Walk navigation type uses mouse drags to rotate
   * and translate the viewer as if they are walking through the content. The
   * Examine type is the default.
   * 
   * @param nav
   *            either Walk or Examine
   */
  public void setNavigationType(int nav) {
    if (nav == Walk) {
      navigationType = Walk;
      if (walkMenuItem != null)
        walkMenuItem.setState(true);
      if (examineMenuItem != null)
        examineMenuItem.setState(false);
      if (walkBehavior != null)
        walkBehavior.setEnable(true);
      if (examineBehavior != null)
        examineBehavior.setEnable(false);
    } else {
      navigationType = Examine;
      if (walkMenuItem != null)
        walkMenuItem.setState(false);
      if (examineMenuItem != null)
        examineMenuItem.setState(true);
      if (walkBehavior != null)
        walkBehavior.setEnable(false);
      if (examineBehavior != null)
        examineBehavior.setEnable(true);
    }
  }

  /**
   * Gets the current navigation type, returning either Walk or Examine.
   * 
   * @return either Walk or Examine
   */
  public int getNavigationType() {
    return navigationType;
  }

  /**
   * Sets whether the scene graph should be compiled or not. Normally this is
   * always a good idea. For some example applications that use this Example
   * framework, it is useful to disable compilation - particularly when nodes
   * and node components will need to be made un-live in order to make
   * changes. Once compiled, such components can be made un-live, but they are
   * still unchangable unless appropriate capabilities have been set.
   * 
   * @param onOff
   *            a boolean turning compilation on (true) or off (false)
   */
  public void setCompilable(boolean onOff) {
    shouldCompile = onOff;
  }

  /**
   * Gets whether the scene graph will be compiled or not.
   * 
   * @return a boolean indicating if scene graph compilation is on or off
   */
  public boolean getCompilable() {
    return shouldCompile;
  }

  //These methods will be replaced
  //  Set the view position and direction
  public void setViewpoint(Point3f position, Vector3f direction) {
    Transform3D t = new Transform3D();
    t.set(new Vector3f(position));
    exampleViewTransform.setTransform(t);
    // how to set direction?
  }

  //  Reset transforms
  public void reset() {
    Transform3D trans = new Transform3D();
    exampleSceneTransform.setTransform(trans);
    trans.set(new Vector3f(0.0f, 0.0f, 10.0f));
    exampleViewTransform.setTransform(trans);
    setNavigationType(navigationType);
  }

  //
  //  Gets the URL (with file: prepended) for the current directory.
  //  This is a terrible hack needed in the Alpha release of Java3D
  //  in order to build a full path URL for loading sounds with
  //  MediaContainer. When MediaContainer is fully implemented,
  //  it should handle relative path names, but not yet.
  //
  public String getCurrentDirectory() {
    // Create a bogus file so that we can query it's path
    File dummy = new File("dummy.tmp");
    String dummyPath = dummy.getAbsolutePath();

    // strip "/dummy.tmp" from end of dummyPath and put into 'path'
    if (dummyPath.endsWith(File.separator + "dummy.tmp")) {
      int index = dummyPath.lastIndexOf(File.separator + "dummy.tmp");
      if (index >= 0) {
        int pathLength = index + 5; // pre-pend 'file:'
        char[] charPath = new char[pathLength];
        dummyPath.getChars(0, index, charPath, 5);
        String path = new String(charPath, 0, pathLength);
        path = "file:" + path.substring(5, pathLength);
        return path + File.separator;
      }
    }
    return dummyPath + File.separator;
  }

  //--------------------------------------------------------------
  //  USER INTERFACE
  //--------------------------------------------------------------

  /**
   * Builds the example AWT Frame menubar. Standard menus and their options
   * are added. Applications that subclass this class should build their
   * menubar additions within their initialize method.
   * 
   * @return a MenuBar for the AWT Frame
   */
  private MenuBar buildMenuBar() {
    // Build the menubar
    MenuBar menuBar = new MenuBar();

    // File menu
    Menu m = new Menu("File");
    m.addActionListener(this);

    m.add("Exit");

    menuBar.add(m);

    // View menu
    m = new Menu("View");
    m.addActionListener(this);

    m.add("Reset view");

    m.addSeparator();

    walkMenuItem = new CheckboxMenuItem("Walk");
    walkMenuItem.addItemListener(this);
    m.add(walkMenuItem);

    examineMenuItem = new CheckboxMenuItem("Examine");
    examineMenuItem.addItemListener(this);
    m.add(examineMenuItem);

    if (navigationType == Walk) {
      walkMenuItem.setState(true);
      examineMenuItem.setState(false);
    } else {
      walkMenuItem.setState(false);
      examineMenuItem.setState(true);
    }

    m.addSeparator();

    headlightMenuItem = new CheckboxMenuItem("Headlight on/off");
    headlightMenuItem.addItemListener(this);
    headlightMenuItem.setState(headlightOnOff);
    m.add(headlightMenuItem);

    menuBar.add(m);

    return menuBar;
  }

  /**
   * Shows the application's frame, making it and its menubar, 3D canvas, and
   * 3D content visible.
   */
  public void showFrame() {
    exampleFrame.show();
  }

  /**
   * Quits the application.
   */
  public void quit() {
    System.exit(0);
  }

  /**
   * Handles menu selections.
   * 
   * @param event
   *            an ActionEvent indicating what menu action requires handling
   */
  public void actionPerformed(ActionEvent event) {
    String arg = event.getActionCommand();
    if (arg.equals("Reset view"))
      reset();
    else if (arg.equals("Exit"))
      quit();
  }

  /**
   * Handles checkbox items on a CheckboxMenu. The Example class has none of
   * its own, but subclasses may have some.
   * 
   * @param menu
   *            which CheckboxMenu needs action
   * @param check
   *            which CheckboxMenu item has changed
   */
  public void checkboxChanged(CheckboxMenu menu, int check) {
    // None for us
  }

  /**
   * Handles on/off checkbox items on a standard menu.
   * 
   * @param event
   *            an ItemEvent indicating what requires handling
   */
  public void itemStateChanged(ItemEvent event) {
    Object src = event.getSource();
    boolean state;
    if (src == headlightMenuItem) {
      state = headlightMenuItem.getState();
      headlight.setEnable(state);
    } else if (src == walkMenuItem)
      setNavigationType(Walk);
    else if (src == examineMenuItem)
      setNavigationType(Examine);
  }

  /**
   * Handles a window closing event notifying the application that the user
   * has chosen to close the application without selecting the "Exit" menu
   * item.
   * 
   * @param event
   *            a WindowEvent indicating the window is closing
   */
  public void windowClosing(WindowEvent event) {
    quit();
  }

  public void windowClosed(WindowEvent event) {
  }

  public void windowOpened(WindowEvent event) {
  }

  public void windowIconified(WindowEvent event) {
  }

  public void windowDeiconified(WindowEvent event) {
  }

  public void windowActivated(WindowEvent event) {
  }

  public void windowDeactivated(WindowEvent event) {
  }

  //  Well known colors, positions, and directions
  public final static Color3f White = new Color3f(1.0f, 1.0f, 1.0f);

  public final static Color3f Gray = new Color3f(0.7f, 0.7f, 0.7f);

  public final static Color3f DarkGray = new Color3f(0.2f, 0.2f, 0.2f);

  public final static Color3f Black = new Color3f(0.0f, 0.0f, 0.0f);

  public final static Color3f Red = new Color3f(1.0f, 0.0f, 0.0f);

  public final static Color3f DarkRed = new Color3f(0.3f, 0.0f, 0.0f);

  public final static Color3f Yellow = new Color3f(1.0f, 1.0f, 0.0f);

  public final static Color3f DarkYellow = new Color3f(0.3f, 0.3f, 0.0f);

  public final static Color3f Green = new Color3f(0.0f, 1.0f, 0.0f);

  public final static Color3f DarkGreen = new Color3f(0.0f, 0.3f, 0.0f);

  public final static Color3f Cyan = new Color3f(0.0f, 1.0f, 1.0f);

  public final static Color3f Blue = new Color3f(0.0f, 0.0f, 1.0f);

  public final static Color3f DarkBlue = new Color3f(0.0f, 0.0f, 0.3f);

  public final static Color3f Magenta = new Color3f(1.0f, 0.0f, 1.0f);

  public final static Vector3f PosX = new Vector3f(1.0f, 0.0f, 0.0f);

  public final static Vector3f NegX = new Vector3f(-1.0f, 0.0f, 0.0f);

  public final static Vector3f PosY = new Vector3f(0.0f, 1.0f, 0.0f);

  public final static Vector3f NegY = new Vector3f(0.0f, -1.0f, 0.0f);

  public final static Vector3f PosZ = new Vector3f(0.0f, 0.0f, 1.0f);

  public final static Vector3f NegZ = new Vector3f(0.0f, 0.0f, -1.0f);

  public final static Point3f Origin = new Point3f(0.0f, 0.0f, 0.0f);

  public final static Point3f PlusX = new Point3f(0.75f, 0.0f, 0.0f);

  public final static Point3f MinusX = new Point3f(-0.75f, 0.0f, 0.0f);

  public final static Point3f PlusY = new Point3f(0.0f, 0.75f, 0.0f);

  public final static Point3f MinusY = new Point3f(0.0f, -0.75f, 0.0f);

  public final static Point3f PlusZ = new Point3f(0.0f, 0.0f, 0.75f);

  public final static Point3f MinusZ = new Point3f(0.0f, 0.0f, -0.75f);
}

//
//INTERFACE
//CheckboxMenuListener - listen for checkbox change events
//
//DESCRIPTION
//The checkboxChanged method is called by users of this class
//to notify the listener when a checkbox choice has changed on
//a CheckboxMenu class menu.
//

interface CheckboxMenuListener extends EventListener {
  public void checkboxChanged(CheckboxMenu menu, int check);
}

/**
 * ExamineViewerBehavior
 * 
 * @version 1.0, 98/04/16
 */

/**
 * Wakeup on mouse button presses, releases, and mouse movements and generate
 * transforms in an "examination style" that enables the user to rotate,
 * translation, and zoom an object as if it is held at arm's length. Such an
 * examination style is similar to the "Examine" navigation type used by VRML
 * browsers.
 * 
 * The behavior maps mouse drags to different transforms depending upon the
 * mosue button held down:
 * 
 * Button 1 (left) Horizontal movement --> Y-axis rotation Vertical movement -->
 * X-axis rotation
 * 
 * Button 2 (middle) Horizontal movement --> nothing Vertical movement -->
 * Z-axis translation
 * 
 * Button 3 (right) Horizontal movement --> X-axis translation Vertical movement
 * --> Y-axis translation
 * 
 * To support systems with 2 or 1 mouse buttons, the following alternate
 * mappings are supported while dragging with any mouse button held down and
 * zero or more keyboard modifiers held down:
 * 
 * No modifiers = Button 1 ALT = Button 2 Meta = Button 3 Control = Button 3
 * 
 * The behavior automatically modifies a TransformGroup provided to the
 * constructor. The TransformGroup's transform can be set at any time by the
 * application or other behaviors to cause the examine rotation and translation
 * to be reset.
 */

// This class is inspired by the MouseBehavior, MouseRotate,
// MouseTranslate, and MouseZoom utility behaviors provided with
// Java 3D. This class differs from those utilities in that it:
//
//    (a) encapsulates all three behaviors into one in order to
//        enforce a specific "Examine" symantic
//
//    (b) supports set/get of the rotation and translation factors
//        that control the speed of movement.
//
//    (c) supports the "Control" modifier as an alternative to the
//        "Meta" modifier not present on PC, Mac, and most non-Sun
//        keyboards. This makes button3 behavior usable on PCs,
//        Macs, and other systems with fewer than 3 mouse buttons.

class ExamineViewerBehavior extends ViewerBehavior {
  // Previous cursor location
  protected int previousX = 0;

  protected int previousY = 0;

  // Saved standard cursor
  protected Cursor savedCursor = null;

  /**
   * Construct an examine behavior that listens to mouse movement and button
   * presses to generate rotation and translation transforms written into a
   * transform group given later with the setTransformGroup( ) method.
   */
  public ExamineViewerBehavior() {
    super();
  }

  /**
   * Construct an examine behavior that listens to mouse movement and button
   * presses to generate rotation and translation transforms written into a
   * transform group given later with the setTransformGroup( ) method.
   * 
   * @param parent
   *            The AWT Component that contains the area generating mouse
   *            events.
   */
  public ExamineViewerBehavior(Component parent) {
    super(parent);
  }

  /**
   * Construct an examine behavior that listens to mouse movement and button
   * presses to generate rotation and translation transforms written into the
   * given transform group.
   * 
   * @param transformGroup
   *            The transform group to be modified by the behavior.
   */
  public ExamineViewerBehavior(TransformGroup transformGroup) {
    super();
    subjectTransformGroup = transformGroup;
  }

  /**
   * Construct an examine behavior that listens to mouse movement and button
   * presses to generate rotation and translation transforms written into the
   * given transform group.
   * 
   * @param transformGroup
   *            The transform group to be modified by the behavior.
   * @param parent
   *            The AWT Component that contains the area generating mouse
   *            events.
   */
  public ExamineViewerBehavior(TransformGroup transformGroup, Component parent) {
    super(parent);
    subjectTransformGroup = transformGroup;
  }

  /**
   * Respond to a button1 event (press, release, or drag).
   * 
   * @param mouseEvent
   *            A MouseEvent to respond to.
   */
  public void onButton1(MouseEvent mev) {
    if (subjectTransformGroup == null)
      return;

    int x = mev.getX();
    int y = mev.getY();

    if (mev.getID() == MouseEvent.MOUSE_PRESSED) {
      // Mouse button pressed: record position
      previousX = x;
      previousY = y;

      // Change to a "move" cursor
      if (parentComponent != null) {
        savedCursor = parentComponent.getCursor();
        parentComponent.setCursor(Cursor
            .getPredefinedCursor(Cursor.HAND_CURSOR));
      }
      return;
    }
    if (mev.getID() == MouseEvent.MOUSE_RELEASED) {
      // Mouse button released: do nothing

      // Switch the cursor back
      if (parentComponent != null)
        parentComponent.setCursor(savedCursor);
      return;
    }

    //
    // Mouse moved while button down: create a rotation
    //
    // Compute the delta in X and Y from the previous
    // position. Use the delta to compute rotation
    // angles with the mapping:
    //
    //   positive X mouse delta --> positive Y-axis rotation
    //   positive Y mouse delta --> positive X-axis rotation
    //
    // where positive X mouse movement is to the right, and
    // positive Y mouse movement is **down** the screen.
    //
    int deltaX = x - previousX;
    int deltaY = y - previousY;

    if (deltaX > UNUSUAL_XDELTA || deltaX < -UNUSUAL_XDELTA
        || deltaY > UNUSUAL_YDELTA || deltaY < -UNUSUAL_YDELTA) {
      // Deltas are too huge to be believable. Probably a glitch.
      // Don't record the new XY location, or do anything.
      return;
    }

    double xRotationAngle = deltaY * XRotationFactor;
    double yRotationAngle = deltaX * YRotationFactor;

    //
    // Build transforms
    //
    transform1.rotX(xRotationAngle);
    transform2.rotY(yRotationAngle);

    // Get and save the current transform matrix
    subjectTransformGroup.getTransform(currentTransform);
    currentTransform.get(matrix);
    translate.set(matrix.m03, matrix.m13, matrix.m23);

    // Translate to the origin, rotate, then translate back
    currentTransform.setTranslation(origin);
    currentTransform.mul(transform1, currentTransform);
    currentTransform.mul(transform2, currentTransform);
    currentTransform.setTranslation(translate);

    // Update the transform group
    subjectTransformGroup.setTransform(currentTransform);

    previousX = x;
    previousY = y;
  }

  /**
   * Respond to a button2 event (press, release, or drag).
   * 
   * @param mouseEvent
   *            A MouseEvent to respond to.
   */
  public void onButton2(MouseEvent mev) {
    if (subjectTransformGroup == null)
      return;

    int x = mev.getX();
    int y = mev.getY();

    if (mev.getID() == MouseEvent.MOUSE_PRESSED) {
      // Mouse button pressed: record position
      previousX = x;
      previousY = y;

      // Change to a "move" cursor
      if (parentComponent != null) {
        savedCursor = parentComponent.getCursor();
        parentComponent.setCursor(Cursor
            .getPredefinedCursor(Cursor.MOVE_CURSOR));
      }
      return;
    }
    if (mev.getID() == MouseEvent.MOUSE_RELEASED) {
      // Mouse button released: do nothing

      // Switch the cursor back
      if (parentComponent != null)
        parentComponent.setCursor(savedCursor);
      return;
    }

    //
    // Mouse moved while button down: create a translation
    //
    // Compute the delta in Y from the previous
    // position. Use the delta to compute translation
    // distances with the mapping:
    //
    //   positive Y mouse delta --> positive Y-axis translation
    //
    // where positive X mouse movement is to the right, and
    // positive Y mouse movement is **down** the screen.
    //
    int deltaY = y - previousY;

    if (deltaY > UNUSUAL_YDELTA || deltaY < -UNUSUAL_YDELTA) {
      // Deltas are too huge to be believable. Probably a glitch.
      // Don't record the new XY location, or do anything.
      return;
    }

    double zTranslationDistance = deltaY * ZTranslationFactor;

    //
    // Build transforms
    //
    translate.set(0.0, 0.0, zTranslationDistance);
    transform1.set(translate);

    // Get and save the current transform
    subjectTransformGroup.getTransform(currentTransform);

    // Translate as needed
    currentTransform.mul(transform1, currentTransform);

    // Update the transform group
    subjectTransformGroup.setTransform(currentTransform);

    previousX = x;
    previousY = y;
  }

  /**
   * Respond to a button3 event (press, release, or drag).
   * 
   * @param mouseEvent
   *            A MouseEvent to respond to.
   */
  public void onButton3(MouseEvent mev) {
    if (subjectTransformGroup == null)
      return;

    int x = mev.getX();
    int y = mev.getY();

    if (mev.getID() == MouseEvent.MOUSE_PRESSED) {
      // Mouse button pressed: record position
      previousX = x;
      previousY = y;

      // Change to a "move" cursor
      if (parentComponent != null) {
        savedCursor = parentComponent.getCursor();
        parentComponent.setCursor(Cursor
            .getPredefinedCursor(Cursor.MOVE_CURSOR));
      }
      return;
    }
    if (mev.getID() == MouseEvent.MOUSE_RELEASED) {
      // Mouse button released: do nothing

      // Switch the cursor back
      if (parentComponent != null)
        parentComponent.setCursor(savedCursor);
      return;
    }

    //
    // Mouse moved while button down: create a translation
    //
    // Compute the delta in X and Y from the previous
    // position. Use the delta to compute translation
    // distances with the mapping:
    //
    //   positive X mouse delta --> positive X-axis translation
    //   positive Y mouse delta --> negative Y-axis translation
    //
    // where positive X mouse movement is to the right, and
    // positive Y mouse movement is **down** the screen.
    //
    int deltaX = x - previousX;
    int deltaY = y - previousY;

    if (deltaX > UNUSUAL_XDELTA || deltaX < -UNUSUAL_XDELTA
        || deltaY > UNUSUAL_YDELTA || deltaY < -UNUSUAL_YDELTA) {
      // Deltas are too huge to be believable. Probably a glitch.
      // Don't record the new XY location, or do anything.
      return;
    }

    double xTranslationDistance = deltaX * XTranslationFactor;
    double yTranslationDistance = -deltaY * YTranslationFactor;

    //
    // Build transforms
    //
    translate.set(xTranslationDistance, yTranslationDistance, 0.0);
    transform1.set(translate);

    // Get and save the current transform
    subjectTransformGroup.getTransform(currentTransform);

    // Translate as needed
    currentTransform.mul(transform1, currentTransform);

    // Update the transform group
    subjectTransformGroup.setTransform(currentTransform);

    previousX = x;
    previousY = y;
  }

  /**
   * Respond to an elapsed frames event (assuming subclass has set up a wakeup
   * criterion for it).
   * 
   * @param time
   *            A WakeupOnElapsedFrames criterion to respond to.
   */
  public void onElapsedFrames(WakeupOnElapsedFrames timeEvent) {
    // Can't happen
  }
}

/*
 * 
 * Copyright (c) 1998 David R. Nadeau
 *  
 */

/**
 * WalkViewerBehavior is a utility class that creates a "walking style"
 * navigation symantic.
 * 
 * The behavior wakes up on mouse button presses, releases, and mouse movements
 * and generates transforms in a "walk style" that enables the user to walk
 * through a scene, translating and turning about as if they are within the
 * scene. Such a walk style is similar to the "Walk" navigation type used by
 * VRML browsers.
 * <P>
 * The behavior maps mouse drags to different transforms depending upon the
 * mouse button held down:
 * <DL>
 * <DT>Button 1 (left)
 * <DD>Horizontal movement --> Y-axis rotation
 * <DD>Vertical movement --> Z-axis translation
 * 
 * <DT>Button 2 (middle)
 * <DD>Horizontal movement --> Y-axis rotation
 * <DD>Vertical movement --> X-axis rotation
 * 
 * <DT>Button 3 (right)
 * <DD>Horizontal movement --> X-axis translation
 * <DD>Vertical movement --> Y-axis translation
 * </DL>
 * 
 * To support systems with 2 or 1 mouse buttons, the following alternate
 * mappings are supported while dragging with any mouse button held down and
 * zero or more keyboard modifiers held down:
 * <UL>
 * <LI>No modifiers = Button 1
 * <LI>ALT = Button 2
 * <LI>Meta = Button 3
 * <LI>Control = Button 3
 * </UL>
 * The behavior automatically modifies a TransformGroup provided to the
 * constructor. The TransformGroup's transform can be set at any time by the
 * application or other behaviors to cause the walk rotation and translation to
 * be reset.
 * <P>
 * While a mouse button is down, the behavior automatically changes the cursor
 * in a given parent AWT Component. If no parent Component is given, no cursor
 * changes are attempted.
 * 
 * @version 1.0, 98/04/16
 * @author David R. Nadeau, San Diego Supercomputer Center
 */

class WalkViewerBehavior extends ViewerBehavior {
  // This class is inspired by the MouseBehavior, MouseRotate,
  // MouseTranslate, and MouseZoom utility behaviors provided with
  // Java 3D. This class differs from those utilities in that it:
  //
  //    (a) encapsulates all three behaviors into one in order to
  //        enforce a specific "Walk" symantic
  //
  //    (b) supports set/get of the rotation and translation factors
  //        that control the speed of movement.
  //
  //    (c) supports the "Control" modifier as an alternative to the
  //        "Meta" modifier not present on PC, Mac, and most non-Sun
  //        keyboards. This makes button3 behavior usable on PCs,
  //        Macs, and other systems with fewer than 3 mouse buttons.

  // Previous and initial cursor locations
  protected int previousX = 0;

  protected int previousY = 0;

  protected int initialX = 0;

  protected int initialY = 0;

  // Deadzone size (delta from initial XY for which no
  // translate or rotate action is taken
  protected static final int DELTAX_DEADZONE = 10;

  protected static final int DELTAY_DEADZONE = 10;

  // Keep a set of wakeup criterion for animation-generated
  // event types.
  protected WakeupCriterion[] mouseAndAnimationEvents = null;

  protected WakeupOr mouseAndAnimationCriterion = null;

  protected WakeupOr savedMouseCriterion = null;

  // Saved standard cursor
  protected Cursor savedCursor = null;

  /**
   * Default Rotation and translation scaling factors for animated movements
   * (Button 1 press).
   */
  public static final double DEFAULT_YROTATION_ANIMATION_FACTOR = 0.0002;

  public static final double DEFAULT_ZTRANSLATION_ANIMATION_FACTOR = 0.01;

  protected double YRotationAnimationFactor = DEFAULT_YROTATION_ANIMATION_FACTOR;

  protected double ZTranslationAnimationFactor = DEFAULT_ZTRANSLATION_ANIMATION_FACTOR;

  /**
   * Constructs a new walk behavior that converts mouse actions into rotations
   * and translations. Rotations and translations are written into a
   * TransformGroup that must be set using the setTransformGroup method. The
   * cursor will be changed during mouse actions if the parent frame is set
   * using the setParentComponent method.
   * 
   * @return a new WalkViewerBehavior that needs its TransformGroup and parent
   *         Component set
   */
  public WalkViewerBehavior() {
    super();
  }

  /**
   * Constructs a new walk behavior that converts mouse actions into rotations
   * and translations. Rotations and translations are written into a
   * TransformGroup that must be set using the setTransformGroup method. The
   * cursor will be changed within the given AWT parent Component during mouse
   * drags.
   * 
   * @param parent
   *            a parent AWT Component within which the cursor will change
   *            during mouse drags
   * 
   * @return a new WalkViewerBehavior that needs its TransformGroup and parent
   *         Component set
   */
  public WalkViewerBehavior(Component parent) {
    super(parent);
  }

  /**
   * Constructs a new walk behavior that converts mouse actions into rotations
   * and translations. Rotations and translations are written into the given
   * TransformGroup. The cursor will be changed during mouse actions if the
   * parent frame is set using the setParentComponent method.
   * 
   * @param transformGroup
   *            a TransformGroup whos transform is read and written by the
   *            behavior
   * 
   * @return a new WalkViewerBehavior that needs its TransformGroup and parent
   *         Component set
   */
  public WalkViewerBehavior(TransformGroup transformGroup) {
    super();
    subjectTransformGroup = transformGroup;
  }

  /**
   * Constructs a new walk behavior that converts mouse actions into rotations
   * and translations. Rotations and translations are written into the given
   * TransformGroup. The cursor will be changed within the given AWT parent
   * Component during mouse drags.
   * 
   * @param transformGroup
   *            a TransformGroup whos transform is read and written by the
   *            behavior
   * 
   * @param parent
   *            a parent AWT Component within which the cursor will change
   *            during mouse drags
   * 
   * @return a new WalkViewerBehavior that needs its TransformGroup and parent
   *         Component set
   */
  public WalkViewerBehavior(TransformGroup transformGroup, Component parent) {
    super(parent);
    subjectTransformGroup = transformGroup;
  }

  /**
   * Initializes the behavior.
   */
  public void initialize() {
    super.initialize();
    savedMouseCriterion = mouseCriterion; // from parent class
    mouseAndAnimationEvents = new WakeupCriterion[4];
    mouseAndAnimationEvents[0] = new WakeupOnAWTEvent(
        MouseEvent.MOUSE_DRAGGED);
    mouseAndAnimationEvents[1] = new WakeupOnAWTEvent(
        MouseEvent.MOUSE_PRESSED);
    mouseAndAnimationEvents[2] = new WakeupOnAWTEvent(
        MouseEvent.MOUSE_RELEASED);
    mouseAndAnimationEvents[3] = new WakeupOnElapsedFrames(0);
    mouseAndAnimationCriterion = new WakeupOr(mouseAndAnimationEvents);
    // Don't use the above criterion until a button 1 down event
  }

  /**
   * Sets the Y rotation animation scaling factor for Y-axis rotations. This
   * scaling factor is used to control the speed of Y rotation when button 1
   * is pressed and dragged.
   * 
   * @param factor
   *            the double Y rotation scaling factor
   */
  public void setYRotationAnimationFactor(double factor) {
    YRotationAnimationFactor = factor;
  }

  /**
   * Gets the current Y animation rotation scaling factor for Y-axis
   * rotations.
   * 
   * @return the double Y rotation scaling factor
   */
  public double getYRotationAnimationFactor() {
    return YRotationAnimationFactor;
  }

  /**
   * Sets the Z animation translation scaling factor for Z-axis translations.
   * This scaling factor is used to control the speed of Z translation when
   * button 1 is pressed and dragged.
   * 
   * @param factor
   *            the double Z translation scaling factor
   */
  public void setZTranslationAnimationFactor(double factor) {
    ZTranslationAnimationFactor = factor;
  }

  /**
   * Gets the current Z animation translation scaling factor for Z-axis
   * translations.
   * 
   * @return the double Z translation scaling factor
   */
  public double getZTranslationAnimationFactor() {
    return ZTranslationAnimationFactor;
  }

  /**
   * Responds to an elapsed frames event. Such an event is generated on every
   * frame while button 1 is held down. On each call, this method computes new
   * Y-axis rotation and Z-axis translation values and writes them to the
   * behavior's TransformGroup. The translation and rotation amounts are
   * computed based upon the distance between the current cursor location and
   * the cursor location when button 1 was pressed. As this distance
   * increases, the translation or rotation amount increases.
   * 
   * @param time
   *            the WakeupOnElapsedFrames criterion to respond to
   */
  public void onElapsedFrames(WakeupOnElapsedFrames timeEvent) {
    //
    // Time elapsed while button down: create a rotation and
    // a translation.
    //
    // Compute the delta in X and Y from the initial position to
    // the previous position. Multiply the delta times a scaling
    // factor to compute an offset to add to the current translation
    // and rotation. Use the mapping:
    //
    //   positive X mouse delta --> negative Y-axis rotation
    //   positive Y mouse delta --> positive Z-axis translation
    //
    // where positive X mouse movement is to the right, and
    // positive Y mouse movement is **down** the screen.
    //
    if (buttonPressed != BUTTON1)
      return;
    int deltaX = previousX - initialX;
    int deltaY = previousY - initialY;

    double yRotationAngle = -deltaX * YRotationAnimationFactor;
    double zTranslationDistance = deltaY * ZTranslationAnimationFactor;

    //
    // Build transforms
    //
    transform1.rotY(yRotationAngle);
    translate.set(0.0, 0.0, zTranslationDistance);

    // Get and save the current transform matrix
    subjectTransformGroup.getTransform(currentTransform);
    currentTransform.get(matrix);

    // Translate to the origin, rotate, then translate back
    currentTransform.setTranslation(origin);
    currentTransform.mul(transform1, currentTransform);

    // Translate back from the origin by the original translation
    // distance, plus the new walk translation... but force walk
    // to travel on a plane by ignoring the Y component of a
    // transformed translation vector.
    currentTransform.transform(translate);
    translate.x += matrix.m03; // add in existing X translation
    translate.y = matrix.m13; // use Y translation
    translate.z += matrix.m23; // add in existing Z translation
    currentTransform.setTranslation(translate);

    // Update the transform group
    subjectTransformGroup.setTransform(currentTransform);
  }

  /**
   * Responds to a button1 event (press, release, or drag). On a press, the
   * method adds a wakeup criterion to the behavior's set, callling for the
   * behavior to be awoken on each frame. On a button prelease, this criterion
   * is removed from the set.
   * 
   * @param mouseEvent
   *            the MouseEvent to respond to
   */
  public void onButton1(MouseEvent mev) {
    if (subjectTransformGroup == null)
      return;

    int x = mev.getX();
    int y = mev.getY();

    if (mev.getID() == MouseEvent.MOUSE_PRESSED) {
      // Mouse button pressed: record position and change
      // the wakeup criterion to include elapsed time wakeups
      // so we can animate.
      previousX = x;
      previousY = y;
      initialX = x;
      initialY = y;

      // Swap criterion... parent class will not reschedule us
      mouseCriterion = mouseAndAnimationCriterion;

      // Change to a "move" cursor
      if (parentComponent != null) {
        savedCursor = parentComponent.getCursor();
        parentComponent.setCursor(Cursor
            .getPredefinedCursor(Cursor.HAND_CURSOR));
      }
      return;
    }
    if (mev.getID() == MouseEvent.MOUSE_RELEASED) {
      // Mouse button released: restore original wakeup
      // criterion which only includes mouse activity, not
      // elapsed time
      mouseCriterion = savedMouseCriterion;

      // Switch the cursor back
      if (parentComponent != null)
        parentComponent.setCursor(savedCursor);
      return;
    }

    previousX = x;
    previousY = y;
  }

  /**
   * Responds to a button2 event (press, release, or drag). On a press, the
   * method records the initial cursor location. On a drag, the difference
   * between the current and previous cursor location provides a delta that
   * controls the amount by which to rotate in X and Y.
   * 
   * @param mouseEvent
   *            the MouseEvent to respond to
   */
  public void onButton2(MouseEvent mev) {
    if (subjectTransformGroup == null)
      return;

    int x = mev.getX();
    int y = mev.getY();

    if (mev.getID() == MouseEvent.MOUSE_PRESSED) {
      // Mouse button pressed: record position
      previousX = x;
      previousY = y;
      initialX = x;
      initialY = y;

      // Change to a "rotate" cursor
      if (parentComponent != null) {
        savedCursor = parentComponent.getCursor();
        parentComponent.setCursor(Cursor
            .getPredefinedCursor(Cursor.MOVE_CURSOR));
      }
      return;
    }
    if (mev.getID() == MouseEvent.MOUSE_RELEASED) {
      // Mouse button released: do nothing

      // Switch the cursor back
      if (parentComponent != null)
        parentComponent.setCursor(savedCursor);
      return;
    }

    //
    // Mouse moved while button down: create a rotation
    //
    // Compute the delta in X and Y from the previous
    // position. Use the delta to compute rotation
    // angles with the mapping:
    //
    //   positive X mouse delta --> negative Y-axis rotation
    //   positive Y mouse delta --> negative X-axis rotation
    //
    // where positive X mouse movement is to the right, and
    // positive Y mouse movement is **down** the screen.
    //
    int deltaX = x - previousX;
    int deltaY = 0;

    if (Math.abs(y - initialY) > DELTAY_DEADZONE) {
      // Cursor has moved far enough vertically to consider
      // it intentional, so get it's delta.
      deltaY = y - previousY;
    }

    if (deltaX > UNUSUAL_XDELTA || deltaX < -UNUSUAL_XDELTA
        || deltaY > UNUSUAL_YDELTA || deltaY < -UNUSUAL_YDELTA) {
      // Deltas are too huge to be believable. Probably a glitch.
      // Don't record the new XY location, or do anything.
      return;
    }

    double xRotationAngle = -deltaY * XRotationFactor;
    double yRotationAngle = -deltaX * YRotationFactor;

    //
    // Build transforms
    //
    transform1.rotX(xRotationAngle);
    transform2.rotY(yRotationAngle);

    // Get and save the current transform matrix
    subjectTransformGroup.getTransform(currentTransform);
    currentTransform.get(matrix);
    translate.set(matrix.m03, matrix.m13, matrix.m23);

    // Translate to the origin, rotate, then translate back
    currentTransform.setTranslation(origin);
    currentTransform.mul(transform2, currentTransform);
    currentTransform.mul(transform1);
    currentTransform.setTranslation(translate);

    // Update the transform group
    subjectTransformGroup.setTransform(currentTransform);

    previousX = x;
    previousY = y;
  }

  /**
   * Responds to a button3 event (press, release, or drag). On a drag, the
   * difference between the current and previous cursor location provides a
   * delta that controls the amount by which to translate in X and Y.
   * 
   * @param mouseEvent
   *            the MouseEvent to respond to
   */
  public void onButton3(MouseEvent mev) {
    if (subjectTransformGroup == null)
      return;

    int x = mev.getX();
    int y = mev.getY();

    if (mev.getID() == MouseEvent.MOUSE_PRESSED) {
      // Mouse button pressed: record position
      previousX = x;
      previousY = y;

      // Change to a "move" cursor
      if (parentComponent != null) {
        savedCursor = parentComponent.getCursor();
        parentComponent.setCursor(Cursor
            .getPredefinedCursor(Cursor.MOVE_CURSOR));
      }
      return;
    }
    if (mev.getID() == MouseEvent.MOUSE_RELEASED) {
      // Mouse button released: do nothing

      // Switch the cursor back
      if (parentComponent != null)
        parentComponent.setCursor(savedCursor);
      return;
    }

    //
    // Mouse moved while button down: create a translation
    //
    // Compute the delta in X and Y from the previous
    // position. Use the delta to compute translation
    // distances with the mapping:
    //
    //   positive X mouse delta --> positive X-axis translation
    //   positive Y mouse delta --> negative Y-axis translation
    //
    // where positive X mouse movement is to the right, and
    // positive Y mouse movement is **down** the screen.
    //
    int deltaX = x - previousX;
    int deltaY = y - previousY;

    if (deltaX > UNUSUAL_XDELTA || deltaX < -UNUSUAL_XDELTA
        || deltaY > UNUSUAL_YDELTA || deltaY < -UNUSUAL_YDELTA) {
      // Deltas are too huge to be believable. Probably a glitch.
      // Don't record the new XY location, or do anything.
      return;
    }

    double xTranslationDistance = deltaX * XTranslationFactor;
    double yTranslationDistance = -deltaY * YTranslationFactor;

    //
    // Build transforms
    //
    translate.set(xTranslationDistance, yTranslationDistance, 0.0);
    transform1.set(translate);

    // Get and save the current transform
    subjectTransformGroup.getTransform(currentTransform);

    // Translate as needed
    currentTransform.mul(transform1);

    // Update the transform group
    subjectTransformGroup.setTransform(currentTransform);

    previousX = x;
    previousY = y;
  }
}

//
//CLASS
//CheckboxMenu - build a menu of grouped checkboxes
//
//DESCRIPTION
//The class creates a menu with one or more CheckboxMenuItem's
//and monitors that menu. When a menu checkbox is picked, the
//previous one is turned off (in radio-button style). Then,
//a given listener's checkboxChanged method is called, passing it
//the menu and the item checked.
//

class CheckboxMenu extends Menu implements ItemListener {
  // State
  protected CheckboxMenuItem[] checks = null;

  protected int current = 0;

  protected CheckboxMenuListener listener = null;

  //  Construct
  public CheckboxMenu(String name, NameValue[] items,
      CheckboxMenuListener listen) {
    this(name, items, 0, listen);
  }

  public CheckboxMenu(String name, NameValue[] items, int cur,
      CheckboxMenuListener listen) {
    super(name);
    current = cur;
    listener = listen;

    if (items == null)
      return;

    checks = new CheckboxMenuItem[items.length];
    for (int i = 0; i < items.length; i++) {
      checks[i] = new CheckboxMenuItem(items[i].name, false);
      checks[i].addItemListener(this);
      add(checks[i]);
    }
    checks[cur].setState(true);
  }

  //  Handle checkbox changed events
  public void itemStateChanged(ItemEvent event) {
    Object src = event.getSource();

    for (int i = 0; i < checks.length; i++) {
      if (src == checks[i]) {
        // Update the checkboxes
        checks[current].setState(false);
        current = i;
        checks[current].setState(true);

        if (listener != null)
          listener.checkboxChanged(this, i);
        return;
      }
    }
  }

  // Methods to get and set state
  public int getCurrent() {
    return current;
  }

  public void setCurrent(int cur) {
    if (cur < 0 || cur >= checks.length)
      return; // ignore out of range choices
    if (checks == null)
      return;
    checks[current].setState(false);
    current = cur;
    checks[current].setState(true);
  }

  public CheckboxMenuItem getSelectedCheckbox() {
    if (checks == null)
      return null;
    return checks[current];
  }

  public void setSelectedCheckbox(CheckboxMenuItem item) {
    if (checks == null)
      return;
    for (int i = 0; i < checks.length; i++) {
      if (item == checks[i]) {
        checks[i].setState(false);
        current = i;
        checks[i].setState(true);
      }
    }
  }
}

/**
 * ViewerBehavior
 * 
 * @version 1.0, 98/04/16
 */

/**
 * Wakeup on mouse button presses, releases, and mouse movements and generate
 * transforms for a transform group. Classes that extend this class impose
 * specific symantics, such as "Examine" or "Walk" viewing, similar to the
 * navigation types used by VRML browsers.
 * 
 * To support systems with 2 or 1 mouse buttons, the following alternate
 * mappings are supported while dragging with any mouse button held down and
 * zero or more keyboard modifiers held down:
 * 
 * No modifiers = Button 1 ALT = Button 2 Meta = Button 3 Control = Button 3
 * 
 * The behavior automatically modifies a TransformGroup provided to the
 * constructor. The TransformGroup's transform can be set at any time by the
 * application or other behaviors to cause the viewer's rotation and translation
 * to be reset.
 */

// This class is inspired by the MouseBehavior, MouseRotate,
// MouseTranslate, and MouseZoom utility behaviors provided with
// Java 3D. This class differs from those utilities in that it:
//
//    (a) encapsulates all three behaviors into one in order to
//        enforce a specific viewing symantic
//
//    (b) supports set/get of the rotation and translation factors
//        that control the speed of movement.
//
//    (c) supports the "Control" modifier as an alternative to the
//        "Meta" modifier not present on PC, Mac, and most non-Sun
//        keyboards. This makes button3 behavior usable on PCs,
//        Macs, and other systems with fewer than 3 mouse buttons.

abstract class ViewerBehavior extends Behavior {
  // Keep track of the transform group who's transform we modify
  // during mouse motion.
  protected TransformGroup subjectTransformGroup = null;

  // Keep a set of wakeup criterion for different mouse-generated
  // event types.
  protected WakeupCriterion[] mouseEvents = null;

  protected WakeupOr mouseCriterion = null;

  // Track which button was last pressed
  protected static final int BUTTONNONE = -1;

  protected static final int BUTTON1 = 0;

  protected static final int BUTTON2 = 1;

  protected static final int BUTTON3 = 2;

  protected int buttonPressed = BUTTONNONE;

  // Keep a few Transform3Ds for use during event processing. This
  // avoids having to allocate new ones on each event.
  protected Transform3D currentTransform = new Transform3D();

  protected Transform3D transform1 = new Transform3D();

  protected Transform3D transform2 = new Transform3D();

  protected Matrix4d matrix = new Matrix4d();

  protected Vector3d origin = new Vector3d(0.0, 0.0, 0.0);

  protected Vector3d translate = new Vector3d(0.0, 0.0, 0.0);

  // Unusual X and Y delta limits.
  protected static final int UNUSUAL_XDELTA = 400;

  protected static final int UNUSUAL_YDELTA = 400;

  protected Component parentComponent = null;

  /**
   * Construct a viewer behavior that listens to mouse movement and button
   * presses to generate rotation and translation transforms written into a
   * transform group given later with the setTransformGroup( ) method.
   */
  public ViewerBehavior() {
    super();
  }

  /**
   * Construct a viewer behavior that listens to mouse movement and button
   * presses to generate rotation and translation transforms written into a
   * transform group given later with the setTransformGroup( ) method.
   * 
   * @param parent
   *            The AWT Component that contains the area generating mouse
   *            events.
   */
  public ViewerBehavior(Component parent) {
    super();
    parentComponent = parent;
  }

  /**
   * Construct a viewer behavior that listens to mouse movement and button
   * presses to generate rotation and translation transforms written into the
   * given transform group.
   * 
   * @param transformGroup
   *            The transform group to be modified by the behavior.
   */
  public ViewerBehavior(TransformGroup transformGroup) {
    super();
    subjectTransformGroup = transformGroup;  }

  /**
   * Construct a viewer behavior that listens to mouse movement and button
   * presses to generate rotation and translation transforms written into the
   * given transform group.
   * 
   * @param transformGroup
   *            The transform group to be modified by the behavior.
   * @param parent
   *            The AWT Component that contains the area generating mouse
   *            events.
   */
  public ViewerBehavior(TransformGroup transformGroup, Component parent) {
    super();
    subjectTransformGroup = transformGroup;
    parentComponent = parent;
  }

  /**
   * Set the transform group modified by the viewer behavior. Setting the
   * transform group to null disables the behavior until the transform group
   * is again set to an existing group.
   * 
   * @param transformGroup
   *            The new transform group to be modified by the behavior.
   */
  public void setTransformGroup(TransformGroup transformGroup) {
    subjectTransformGroup = transformGroup;
  }

  /**
   * Get the transform group modified by the viewer behavior.
   */
  public TransformGroup getTransformGroup() {
    return subjectTransformGroup;
  }

  /**
   * Sets the parent component who's cursor will be changed during mouse
   * drags. If no component is given is given to the constructor, or set via
   * this method, no cursor changes will be done.
   * 
   * @param parent
   *            the AWT Component, such as a Frame, within which cursor
   *            changes should take place during mouse drags
   */
  public void setParentComponent(Component parent) {
    parentComponent = parent;
  }

  /*
   * Gets the parent frame within which the cursor changes during mouse drags.
   * 
   * @return the AWT Component, such as a Frame, within which cursor changes
   * should take place during mouse drags. Returns null if no parent is set.
   */
  public Component getParentComponent() {
    return parentComponent;
  }

  /**
   * Initialize the behavior.
   */
  public void initialize() {
    // Wakeup when the mouse is dragged or when a mouse button
    // is pressed or released.
    mouseEvents = new WakeupCriterion[3];
    mouseEvents[0] = new WakeupOnAWTEvent(MouseEvent.MOUSE_DRAGGED);
    mouseEvents[1] = new WakeupOnAWTEvent(MouseEvent.MOUSE_PRESSED);
    mouseEvents[2] = new WakeupOnAWTEvent(MouseEvent.MOUSE_RELEASED);
    mouseCriterion = new WakeupOr(mouseEvents);
    wakeupOn(mouseCriterion);
  }

  /**
   * Process a new wakeup. Interpret mouse button presses, releases, and mouse
   * drags.
   * 
   * @param criteria
   *            The wakeup criteria causing the behavior wakeup.
   */
  public void processStimulus(Enumeration criteria) {
    WakeupCriterion wakeup = null;
    AWTEvent[] event = null;
    int whichButton = BUTTONNONE;

    // Process all pending wakeups
    while (criteria.hasMoreElements()) {
      wakeup = (WakeupCriterion) criteria.nextElement();
      if (wakeup instanceof WakeupOnAWTEvent) {
        event = ((WakeupOnAWTEvent) wakeup).getAWTEvent();

        // Process all pending events
        for (int i = 0; i < event.length; i++) {
          if (event[i].getID() != MouseEvent.MOUSE_PRESSED
              && event[i].getID() != MouseEvent.MOUSE_RELEASED
              && event[i].getID() != MouseEvent.MOUSE_DRAGGED)
            // Ignore uninteresting mouse events
            continue;

          //
          // Regretably, Java event handling (or perhaps
          // underlying OS event handling) doesn't always
          // catch button bounces (redundant presses and
          // releases), or order events so that the last
          // drag event is delivered before a release.
          // This means we can get stray events that we
          // filter out here.
          //
          if (event[i].getID() == MouseEvent.MOUSE_PRESSED
              && buttonPressed != BUTTONNONE)
            // Ignore additional button presses until a release
            continue;

          if (event[i].getID() == MouseEvent.MOUSE_RELEASED
              && buttonPressed == BUTTONNONE)
            // Ignore additional button releases until a press
            continue;

          if (event[i].getID() == MouseEvent.MOUSE_DRAGGED  && buttonPressed == BUTTONNONE)
            // Ignore drags until a press
            continue;

          MouseEvent mev = (MouseEvent) event[i];
          int modifiers = mev.getModifiers();

          //
          // Unfortunately, the underlying event handling
          // doesn't do a "grab" operation when a mouse button
          // is pressed. This means that once a button is
          // pressed, if another mouse button or a keyboard
          // modifier key is pressed, the delivered mouse event
          // will show that a different button is being held
          // down. For instance:
          //
          // Action Event
          //  Button 1 press Button 1 press
          //  Drag with button 1 down Button 1 drag
          //  ALT press -
          //  Drag with ALT & button 1 down Button 2 drag
          //  Button 1 release Button 2 release
          //
          // The upshot is that we can get a button press
          // without a matching release, and the button
          // associated with a drag can change mid-drag.
          //
          // To fix this, we watch for an initial button
          // press, and thenceforth consider that button
          // to be the one held down, even if additional
          // buttons get pressed, and despite what is
          // reported in the event. Only when a button is
          // released, do we end such a grab.
          //

          if (buttonPressed == BUTTONNONE) {
            // No button is pressed yet, figure out which
            // button is down now and how to direct events
            if (((modifiers & InputEvent.BUTTON3_MASK) != 0)
                || (((modifiers & InputEvent.BUTTON1_MASK) != 0) && 
    ((modifiers & InputEvent.CTRL_MASK) == InputEvent.CTRL_MASK))) {
              // Button 3 activity (META or CTRL down)
              whichButton = BUTTON3;
            } else if ((modifiers & InputEvent.BUTTON2_MASK) != 0) {
              // Button 2 activity (ALT down)
              whichButton = BUTTON2;
            } else {
              // Button 1 activity (no modifiers down)
              whichButton = BUTTON1;
            }

            // If the event is to press a button, then
            // record that that button is now down
            if (event[i].getID() == MouseEvent.MOUSE_PRESSED)
              buttonPressed = whichButton;
          } else {
            // Otherwise a button was pressed earlier and
            // hasn't been released yet. Assign all further
            // events to it, even if ALT, META, CTRL, or
            // another button has been pressed as well.
            whichButton = buttonPressed;
          }

          // Distribute the event
          switch (whichButton) {
          case BUTTON1:
            onButton1(mev);
            break;
          case BUTTON2:
            onButton2(mev);
            break;
          case BUTTON3:
            onButton3(mev);
            break;
          default:
            break;
          }

          // If the event is to release a button, then
          // record that that button is now up
          if (event[i].getID() == MouseEvent.MOUSE_RELEASED)
            buttonPressed = BUTTONNONE;
        }
        continue;
      }

      if (wakeup instanceof WakeupOnElapsedFrames) {
        onElapsedFrames((WakeupOnElapsedFrames) wakeup);
        continue;
      }
    }

    // Reschedule us for another wakeup
    wakeupOn(mouseCriterion);
  }

  /**
   * Default X and Y rotation factors, and XYZ translation factors.
   */
  public static final double DEFAULT_XROTATION_FACTOR = 0.02;

  public static final double DEFAULT_YROTATION_FACTOR = 0.005;

  public static final double DEFAULT_XTRANSLATION_FACTOR = 0.02;

  public static final double DEFAULT_YTRANSLATION_FACTOR = 0.02;

  public static final double DEFAULT_ZTRANSLATION_FACTOR = 0.04;

  protected double XRotationFactor = DEFAULT_XROTATION_FACTOR;

  protected double YRotationFactor = DEFAULT_YROTATION_FACTOR;

  protected double XTranslationFactor = DEFAULT_XTRANSLATION_FACTOR;

  protected double YTranslationFactor = DEFAULT_YTRANSLATION_FACTOR;

  protected double ZTranslationFactor = DEFAULT_ZTRANSLATION_FACTOR;

  /**
   * Set the X rotation scaling factor for X-axis rotations.
   * 
   * @param factor
   *            The new scaling factor.
   */
  public void setXRotationFactor(double factor) {
    XRotationFactor = factor;
  }

  /**
   * Get the current X rotation scaling factor for X-axis rotations.
   */
  public double getXRotationFactor() {
    return XRotationFactor;
  }

  /**
   * Set the Y rotation scaling factor for Y-axis rotations.
   * 
   * @param factor
   *            The new scaling factor.
   */
  public void setYRotationFactor(double factor) {
    YRotationFactor = factor;
  }

  /**
   * Get the current Y rotation scaling factor for Y-axis rotations.
   */
  public double getYRotationFactor() {
    return YRotationFactor;
  }

  /**
   * Set the X translation scaling factor for X-axis translations.
   * 
   * @param factor
   *            The new scaling factor.
   */
  public void setXTranslationFactor(double factor) {
    XTranslationFactor = factor;
  }

  /**
   * Get the current X translation scaling factor for X-axis translations.
   */
  public double getXTranslationFactor() {
    return XTranslationFactor;
  }

  /**
   * Set the Y translation scaling factor for Y-axis translations.
   * 
   * @param factor
   *            The new scaling factor.
   */
  public void setYTranslationFactor(double factor) {
    YTranslationFactor = factor;
  }

  /**
   * Get the current Y translation scaling factor for Y-axis translations.
   */
  public double getYTranslationFactor() {
    return YTranslationFactor;
  }

  /**
   * Set the Z translation scaling factor for Z-axis translations.
   * 
   * @param factor
   *            The new scaling factor.
   */
  public void setZTranslationFactor(double factor) {
    ZTranslationFactor = factor;
  }

  /**
   * Get the current Z translation scaling factor for Z-axis translations.
   */
  public double getZTranslationFactor() {
    return ZTranslationFactor;
  }

  /**
   * Respond to a button1 event (press, release, or drag).
   * 
   * @param mouseEvent
   *            A MouseEvent to respond to.
   */
  public abstract void onButton1(MouseEvent mouseEvent);

  /**
   * Respond to a button2 event (press, release, or drag).
   * 
   * @param mouseEvent
   *            A MouseEvent to respond to.*/
  public abstract void onButton2(MouseEvent mouseEvent);

  /**
   * Responed to a button3 event (press, release, or drag).
   * 
   * @param mouseEvent
   *            A MouseEvent to respond to.
   */
  public abstract void onButton3(MouseEvent mouseEvent);

  /**
   * Respond to an elapsed frames event (assuming subclass has set up a wakeup
   * criterion for it).
   * 
   * @param time
   *            A WakeupOnElapsedFrames criterion to respond to.
   */
  public abstract void onElapsedFrames(WakeupOnElapsedFrames timeEvent);
}

//
//CLASS
//NameValue - create a handy name-value pair
//
//DESCRIPTION
//It is frequently handy to have one or more name-value pairs
//with which to store named colors, named positions, named textures,
//and so forth. Several of the examples use this class.
//
//AUTHOR
//David R. Nadeau / San Diego Supercomputer Center
//

class NameValue {
  public String name;

  public Object value;

  public NameValue(String n, Object v) {
    name = n;
    value = v;
  }
}