Update vertices of a model during runtime

Question

Hello,
I’m writing a program using Java3D in which I read a model (composed of one 3d surface) from an obj file, I display the model correctly. Then I would like to modify the position of the vertices “live” of this model. This operation can be done many times. I did several attempts based on some examples, but it still doesn’t work. The first errors where related to the capabilities (I guess I fixed that) and then, I don’t have errors, but nothing happens on the screen (the model is still the same). I’m suspecting that there is no link between the geometry (vertices) and the scene, but I don’t know how to connect them.
Do you know why it doesn’t work in the solution that I tried? Does anyone know how to do this in a better way? I’m a beginner with java3d, am I missing something?
Thank you for your help in advance.
Slim.
//  Loading the model correctly
    // using ncsa Portfolio loader packages
     Scene s = null;
       ModelLoader modelLoader = new ModelLoader();
     try {
       s = modelLoader.load(fnm);   // handles many types of file
     catch (Exception e) {
       System.err.println(e);
       System.exit(1);
    sceneGroup = s.getSceneGroup();
    // I added the attribute (Shape3D shape) to have a reference on the model.
    shape = (Shape3D) sceneGroup.getChild(0);
// I added all the capabilities (may be some are unneeded but, to avoid any error related to this)
    shape.setCapability(Shape3D.ALLOW_APPEARANCE_READ);
    shape.setCapability(Shape3D.ALLOW_APPEARANCE_WRITE);
    shape.setCapability(Shape3D.ALLOW_GEOMETRY_READ);
    shape.setCapability(Shape3D.ALLOW_GEOMETRY_WRITE);
    shape.setCapability(GeometryArray.ALLOW_COLOR_READ);
    shape.setCapability(GeometryArray.ALLOW_FORMAT_READ);
    shape.setCapability(GeometryArray.ALLOW_COUNT_READ);
    shape.setCapability(GeometryArray.ALLOW_COORDINATE_READ);
    shape.setCapability(IndexedGeometryArray.ALLOW_COORDINATE_INDEX_READ);
// this part of code is to get the geometry
// vertices is an attribute (array of Point3f)
// ga is an attribute (GeometryArray)
     ga = (GeometryArray)shape.getGeometry();
     verticesNum = ga.getVertexCount();
     GeometryInfo gi = new GeometryInfo(ga);
     vertices = gi.getCoordinates();
  // create a transform group for the object's bounding sphere
    TransformGroup objBoundsTG = new TransformGroup();
    sceneGroup.setCapability(BranchGroup.ALLOW_CHILDREN_READ);
    sceneGroup.setCapability(BranchGroup.ALLOW_CHILDREN_WRITE);
    sceneGroup.setCapability(GeometryArray.ALLOW_COUNT_READ);
    objBoundsTG.addChild( sceneGroup );
// Other code regarding the Transformation ..
// At this level I have some data in the array vertices.And this the code I use to update the vertices of the model:
public void updateGeometry(){
ga.updateData(new GeometryUpdater(){
        public void updateData(Geometry geometry){
          updateVertices();
shape.setGeometry(ga);
  private void updateVertices() {
// Modify the values of the vertices ..
        vertices[i ].x += XX ;
        vertices[i ].y += YY;
        vertices[i ].z += ZZ;
}

Answer 1

I'm putting a complete (and simplified though) runnable code, that might help to understand the problem. It is composed of 3 files.
It needs an object file name to be modified in the main().
Slim.
File: VisObj.java
// File: VisObj.java
import javax.media.j3d.*;
import javax.vecmath.*;
import com.sun.j3d.loaders.*;
import com.sun.j3d.utils.geometry.*;
import com.sun.j3d.loaders.objectfile.ObjectFile;
public class VisObj
  private TransformGroup moveTG, rotTG, scaleTG;
  public Shape3D shape;
  private int verticesNum = 4000;
  private Point3f [] vertices = new Point3f[verticesNum];
  private GeometryArray ga;
  private BranchGroup sceneGroup;
  public VisObj(String fileName)
     Scene s = null;
     try {
            ObjectFile loader = new ObjectFile ();
       s = loader.load(fileName);
     catch (Exception e) {
       System.err.println(e);
       System.exit(1);
    sceneGroup = s.getSceneGroup();
    shape = (Shape3D) sceneGroup.getChild(0);
    shape.setCapability(Shape3D.ALLOW_APPEARANCE_READ);
    shape.setCapability(Shape3D.ALLOW_APPEARANCE_WRITE);
    shape.setCapability(Shape3D.ALLOW_GEOMETRY_READ);
    shape.setCapability(Shape3D.ALLOW_GEOMETRY_WRITE);
    shape.setCapability(GeometryArray.ALLOW_COLOR_READ);
    shape.setCapability(GeometryArray.ALLOW_FORMAT_READ);
    shape.setCapability(GeometryArray.ALLOW_COUNT_READ);
    shape.setCapability(GeometryArray.ALLOW_COORDINATE_READ);
    shape.setCapability(IndexedGeometryArray.ALLOW_COORDINATE_INDEX_READ);
     ga = (GeometryArray)shape.getGeometry();
                verticesNum = ga.getVertexCount();
                System.out.println("Number of verts is " + verticesNum);
                GeometryInfo gi = new GeometryInfo(ga);
                vertices = gi.getCoordinates();
                ga.setCapability(GeometryArray.ALLOW_REF_DATA_WRITE);
                ga.setCapability(GeometryArray.ALLOW_REF_DATA_READ);
    // create a transform group for the object's bounding sphere
    TransformGroup objBoundsTG = new TransformGroup();
    sceneGroup.setCapability(BranchGroup.ALLOW_CHILDREN_READ);
    sceneGroup.setCapability(BranchGroup.ALLOW_CHILDREN_WRITE);
    sceneGroup.setCapability(GeometryArray.ALLOW_COUNT_READ);
    objBoundsTG.addChild( sceneGroup );
    BoundingSphere objBounds = (BoundingSphere) sceneGroup.getBounds();
    double radius = objBounds.getRadius();
    Transform3D objectTrans = new Transform3D();
    objBoundsTG.getTransform( objectTrans );
    Transform3D scaleTrans = new Transform3D();
    double scaleFactor = 1.0/radius;
    scaleTrans.setScale( scaleFactor );
    objectTrans.mul(scaleTrans);
    objBoundsTG.setTransform(objectTrans);
    // create a transform group for scaling the object
    scaleTG = new TransformGroup();
    scaleTG.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
    scaleTG.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
    scaleTG.addChild( objBoundsTG );
    // create a transform group for rotating the object
    rotTG = new TransformGroup();
    rotTG.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
    rotTG.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
    rotTG.addChild( scaleTG );
    // create a transform group for moving the object
    moveTG = new TransformGroup();
    moveTG.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
    moveTG.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
    moveTG.addChild( rotTG );
public void updateGeometry(){
      ga.updateData(new GeometryUpdater(){
        public void updateData(Geometry geometry){
          updateVertices();
      shape.setGeometry(ga);
  private void updateVertices() {
      for (int i = 0; i < verticesNum; i ++) {
        vertices[i ].x +=5 ;
        vertices[i ].y +=10;
        vertices[i ].z = 10;
  public TransformGroup getTG()  {  return moveTG; }
}  File: VisPanel.java
// File VisPanel.java
import javax.swing.*;
import java.awt.*;
import com.sun.j3d.utils.universe.*;
import javax.media.j3d.*;
import javax.vecmath.*;
public class VisPanel extends JPanel
  private SimpleUniverse su;
  private BranchGroup sceneBG;
  private BoundingSphere bounds;
  private VisObj visobj;
  public VisPanel(String fileName)
    setLayout( new BorderLayout() );
    setOpaque( false );
    setPreferredSize( new Dimension(512, 512));
    visobj = new VisObj(fileName);
    GraphicsConfiguration config =
          SimpleUniverse.getPreferredConfiguration();
    Canvas3D canvas3D = new Canvas3D(config);
    add("Center", canvas3D);
    su = new SimpleUniverse(canvas3D);
    createSceneGraph();
    su.addBranchGraph( sceneBG );
  private void createSceneGraph()
    sceneBG = new BranchGroup();
    bounds = new BoundingSphere(new Point3d(0,0,0), 100);
    lightScene();     
    sceneBG.addChild( visobj.getTG() );
    sceneBG.setCapability(BranchGroup.ALLOW_CHILDREN_READ);
    sceneBG.setCapability(BranchGroup.ALLOW_CHILDREN_WRITE);
    sceneBG.setCapability(BranchGroup.ALLOW_CHILDREN_EXTEND);
    sceneBG.setCapability(BranchGroup.ALLOW_DETACH);
    sceneBG.compile();
  private void lightScene()
    Color3f white = new Color3f(1.0f, 1.0f, 1.0f);
    AmbientLight ambientLightNode = new AmbientLight(white);
    ambientLightNode.setInfluencingBounds(bounds);
    sceneBG.addChild(ambientLightNode);
    Vector3f light1Direction  = new Vector3f(-1.0f, -1.0f, -1.0f);
    DirectionalLight light =  new DirectionalLight(white, light1Direction);
    light.setInfluencingBounds(bounds);
    sceneBG.addChild(light);
  public void modifyObject()
  {    visobj.updateGeometry();   }
} File: VisPlayer.java
// File: VisPlayer.java
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class VisPlayer extends JFrame
  private VisPanel vp;   
  private JButton modifyobj;
  public VisPlayer(String fileName)
    super("VisPlayer");
    vp = new VisPanel(fileName);
     Container c = getContentPane();
    c.setLayout( new BorderLayout() );
    c.add(vp, BorderLayout.CENTER);
    JPanel p=new JPanel();
    modifyobj=new JButton("Ok");
    modifyobj.addActionListener(new ActionListener(){
        public void actionPerformed(ActionEvent e) {
        vp.modifyObject();
    p.add(modifyobj,BorderLayout.CENTER);
    c.add(p,BorderLayout.NORTH);
    setDefaultCloseOperation( JFrame.EXIT_ON_CLOSE );
    pack();
    setResizable(false);
    setVisible(true);
  public static void main(String[] args)
  { new VisPlayer("hand1.obj"); }
}