Changing position at runtime

Question

I have an object in my java application, and I would like it to move to x,y, and z coordinates that are constantly changed. The problem is that createSceneGraph seems to be called only once, it isn't a constantly updating thing. Here is the code I have so far, does anyone have any ideas on how I could implement this?
The HeliListener interface calls onUpdate(Heli) whenever the position is changed.
import java.awt.GraphicsConfiguration;
import java.io.File;
import java.io.FileNotFoundException;
import java.net.MalformedURLException;
import java.net.URL;
import javax.media.j3d.AmbientLight;
import javax.media.j3d.Background;
import javax.media.j3d.BoundingSphere;
import javax.media.j3d.BranchGroup;
import javax.media.j3d.Canvas3D;
import javax.media.j3d.DirectionalLight;
import javax.media.j3d.Transform3D;
import javax.media.j3d.TransformGroup;
import javax.vecmath.Color3f;
import javax.vecmath.Point3d;
import javax.vecmath.Vector3f;
import org.Heli;
import org.HeliListener;
import com.sun.j3d.loaders.IncorrectFormatException;
import com.sun.j3d.loaders.ParsingErrorException;
import com.sun.j3d.loaders.Scene;
import com.sun.j3d.loaders.objectfile.ObjectFile;
import com.sun.j3d.utils.behaviors.mouse.MouseRotate;
import com.sun.j3d.utils.behaviors.mouse.MouseTranslate;
import com.sun.j3d.utils.behaviors.mouse.MouseZoom;
import com.sun.j3d.utils.geometry.ColorCube;
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.ViewingPlatform;
public class ObjLoad implements HeliListener {
    private double creaseAngle = 60.0;
    private URL filename = null;
    private SimpleUniverse u;
    private BoundingSphere bounds = new BoundingSphere(new Point3d(0.0,0.0,0.0), 600.0);
    TransformGroup objTrans;
    BranchGroup objRoot;
    protected Canvas3D c;
    //x, y, and z coordinates of Helicopter
    private float   x=0,
                        y=0,
                        z=1;
    private static boolean isFreeLook = true;
    public BranchGroup createSceneGraph()
          // Create the root of the branch graph
          objRoot = new BranchGroup();
        // Create a Transformgroup to scale all objects so they
        // appear in the scene.
        TransformGroup objScale = new TransformGroup();
        Transform3D t3d = new Transform3D();
        t3d.setScale(0.7);
        objScale.setTransform(t3d);
        objRoot.addChild(objScale);
          // Create the transform group node and initialize it to the
          // identity.  Enable the TRANSFORM_WRITE capability so that
          // our behavior code can modify it at runtime.  Add it to the
          // root of the subgraph.
          objTrans = new TransformGroup();
          objTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
          objTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
          objScale.addChild(objTrans);
          int flags = ObjectFile.RESIZE;
          flags |= ObjectFile.TRIANGULATE;
          //flags |= ObjectFile.STRIPIFY;
          ObjectFile f = new ObjectFile(flags, (float)(creaseAngle * Math.PI / 180.0));
          Scene s = null;
          //Try to load the model
          try {
            s = f.load(filename);
          catch (FileNotFoundException e) {
            System.err.println(e);
            System.exit(1);
          catch (ParsingErrorException e) {
            System.err.println(e);
            System.exit(1);
          catch (IncorrectFormatException e) {
            System.err.println(e);
            System.exit(1);
          //Add the model
          objTrans.addChild(s.getSceneGroup());
          //Get the black and green grid and add it.
          MapGrid grid = new MapGrid();
          objRoot.addChild(grid.getGrid());
        //Create the background sphere that contains everything. default color is black
        Background bg = new Background();
        bg.setApplicationBounds(bounds);
        BranchGroup backGeoBranch = new BranchGroup();
        Sphere sphereObj = new Sphere(1.0f, Sphere.GENERATE_NORMALS |
                         Sphere.GENERATE_NORMALS_INWARD |
                      Sphere.GENERATE_TEXTURE_COORDS, 45);
        backGeoBranch.addChild(sphereObj);
        bg.setGeometry(backGeoBranch);
        objTrans.addChild(bg);
        //Sets a transform3D so we can modify the placement of the helicopter
          Transform3D yAxis = new Transform3D();
          objTrans.getTransform(yAxis);
          Vector3f v3f = new Vector3f(x,z,y);
          yAxis.set(v3f);
          objTrans.setTransform(yAxis);
          objRoot.compile();
          return objRoot;
    public ObjLoad(Heli heli)
         heli.addListener(this);
         //Try to get the full filename
          if (filename == null)
              try
                  String path = new File("").getAbsolutePath();
                  filename = new URL("file://" + path + "/models/Helicopter.obj");
              catch (MalformedURLException e)
                   System.err.println(e);
                   System.exit(1);
         GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration();
         c = new Canvas3D(config);
          // Create a simple scene and attach it to the virtual universe
          BranchGroup scene = createSceneGraph();
          u = new SimpleUniverse(c);
        // This will move the ViewPlatform back a bit so the
        // objects in the scene can be viewed.
          ViewingPlatform viewingPlatform = u.getViewingPlatform();
          viewingPlatform.setNominalViewingTransform();
        TransformGroup viewTrans = viewingPlatform.getViewPlatformTransform();
           * The following code sets up the scene lighting
                    //Setup the scene geometry for the lights
                    PlatformGeometry pg = new PlatformGeometry();
                    // Set up the ambient light
                    Color3f ambientColor = new Color3f(0.1f, 0.1f, 0.1f);
                    AmbientLight ambientLightNode = new AmbientLight(ambientColor);
                    ambientLightNode.setInfluencingBounds(bounds);
                    pg.addChild(ambientLightNode);
                    ambientLightNode.setInfluencingBounds(bounds);
                    // Set up the direction and color of directional lights
                    Color3f light1Color = new Color3f(1.0f, 1.0f, 0.9f);
                    Vector3f light1Direction  = new Vector3f(1.0f, 1.0f, 1.0f);
                    Color3f light2Color = new Color3f(1.0f, 1.0f, 1.0f);
                    Vector3f light2Direction  = new Vector3f(-1.0f, -1.0f, -1.0f);
                    //Make the first light
                    DirectionalLight light1
                        = new DirectionalLight(light1Color, light1Direction);
                    light1.setInfluencingBounds(bounds);
                    pg.addChild(light1);
                    //Make the second light
                    DirectionalLight light2
                        = new DirectionalLight(light2Color, light2Direction);
                    light2.setInfluencingBounds(bounds);
                    pg.addChild(light2);
          //Add the Platform geometry (containing the lights) to the viewing platform
          viewingPlatform.setPlatformGeometry( pg );
          // This will move the ViewPlatform back a bit so the
          // objects in the scene can be viewed.
          viewingPlatform.setNominalViewingTransform();
          //Create a branchgroup for the mouse movement
          BranchGroup mouseGroup = new BranchGroup();
          if(isFreeLook){
               //Create the rotate behavior node
             MouseRotate behavior1 = new MouseRotate(viewTrans);
             behavior1.setSchedulingBounds(bounds);
             System.out.println(behavior1.getXFactor() + "  "+behavior1.getYFactor());
             //Mouse becomes hard to control with default factor, so we scale it down a little, default is .03
             behavior1.setFactor(.001,.001);
             mouseGroup.addChild(behavior1);
             // Create the zoom behavior node
             MouseZoom behavior2 = new MouseZoom(viewTrans);
             behavior2.setSchedulingBounds(bounds);
             mouseGroup.addChild(behavior2);
             // Create the translate behavior node
             MouseTranslate behavior3 = new MouseTranslate(viewTrans);
             behavior3.setSchedulingBounds(bounds);
             mouseGroup.addChild(behavior3);
          else //(is Centered view)
        mouseGroup.compile();
        scene.compile();
        u.addBranchGraph(scene);
        u.addBranchGraph(mouseGroup);
     public Canvas3D getCanvas() {
          return c;
     public void onUpdate(Heli heli)
        x = heli.getState().x;
        y = heli.getState().y;
        z = heli.getState().z;
        update(9,9,3);
        System.out.println("Entered...");
     public void update(float x, float y, float z){
          objRoot.removeChild(objTrans);
          objTrans = null;
          Transform3D yAxis = new Transform3D();
          objTrans.getTransform(yAxis);
          Vector3f v3f = new Vector3f(x, z, y);
          yAxis.set(v3f);
          objTrans.setTransform(yAxis);
          objRoot.addChild(objTrans);
}Thanks for any help!

Answer 1

and I would like it to move to x,y, and z coordinates that are constantly changedYou need to implement a Behavior and attach it to a Node that is a parent to the objects you want to animate. The Behavior framework is really easy to implement and for your implementation you might like to try a WakeupCriterion Object, ie WakeupOnElapsedFrames(0), and keep track of the position in a Transform.
The Behavior leaf node provides a framework for adding user-defined actions into the scene graph. Behavior is an abstract class that defines two methods that must be overridden by a subclass: An initialization method, called once when the behavior becomes "live," and a processStimulus method called whenever appropriate by the Java 3D behavior scheduler. The Behavior node also contains an enable flag, a scheduling region, a scheduling interval, and a wakeup condition.
See the javadoc for javax.media.j3d.Behavior. You might like to look at Alpha as well.
Hope that helps you out.
regards