Java-3d collision detection

Question

I have just started to use java 3-d and Im trying to make a game where you jump on enemies to get ponts. I know how to do everything for the game except the collision detection. I need the player ball to be removed when the enemy ball touches it. I have tried to do a id statement that looks like this if(sphere.getBounds().intersects(sphere2.getBounds()) but that trigers it at the same time as the game starts for some reason. I know that I probably need to use the WakeupOnCollisionEntry class but I don't know how to properly use it to remove the player ball. I would think that it would work if I used the WakeupOnCollisionEntry class in conjunction with objTrans.removeChild(sphere) but I have no idea how to use them in conjunction with each others.

If you need to see my code to be able to help, here it is:

package Game;

import com.sun.j3d.utils.geometry.*;
import com.sun.j3d.utils.universe.*;
import java.awt.*;
import java.awt.event.*;
import javax.media.j3d.*;
import javax.swing.JFrame;
import javax.swing.Timer;
import javax.vecmath.*;

public class PAPITest extends JFrame implements ActionListener,KeyListener{
    private TransformGroup objTrans,objTrans2;
    private Transform3D trans = new Transform3D();
    private BranchGroup objRoot;
    private Sphere sphere, sphere2;
    private float x, dx, height = 0.0f, sign = 1.0f, xloc = 0.0f;
    private Timer timer;

    public BranchGroup createSceneGraph(){
        objRoot = new BranchGroup();
        objTrans = new TransformGroup();
        objTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
        objRoot.addChild(objTrans);
        sphere = new Sphere(0.25f);
        sphere.setCollidable(true);
        objTrans = new TransformGroup();
        objTrans.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
        Transform3D pos1 = new Transform3D();
        pos1.setTranslation(new Vector3f(0.0f,0.0f,0.0f));
        objTrans.setTransform(pos1);
        objTrans.addChild(sphere);
        objRoot.addChild(objTrans);
        BoundingSphere bounds = new BoundingSphere
                (new Point3d(0.0,0.0,0.0),100.0);
        Color3f light1Color = new Color3f(0.2f,1.0f,1.0f);
        Vector3f light1Direction = new Vector3f(+4.0f,-7.0f,-12.0f);
        DirectionalLight light1 = new DirectionalLight
                (light1Color,light1Direction);
        light1.setInfluencingBounds(bounds);
        objRoot.addChild(light1);
        Color3f ambientColor = new Color3f(1.0f,1.0f,1.0f);
        AmbientLight ambientLightNode = new AmbientLight(ambientColor);
        ambientLightNode.setInfluencingBounds(bounds);
        objRoot.addChild(ambientLightNode);         
        return objRoot;
    }

    public BranchGroup createSceneGraph2(){
        objRoot = new BranchGroup();
        objTrans2 = new TransformGroup();
        objTrans2.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
        objRoot.addChild(objTrans2);
        sphere2 = new Sphere(0.25f);
        sphere2.setCollidable(true);
        objTrans2 = new TransformGroup();
        objTrans2.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
        Transform3D pos1 = new Transform3D();
        pos1.setTranslation(new Vector3f(0.0f,0.0f,0.0f));
        objTrans2.setTransform(pos1);
        objTrans2.addChild(sphere2);
        objRoot.addChild(objTrans2);
        return objRoot;
    }

    public PAPITest(){
        setLayout(new BorderLayout());
        setTitle("PAPI");
        setVisible(true);
        setSize(505,525);
        setResizable(false);
        setLocationRelativeTo(null);
        setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        GraphicsConfiguration config = SimpleUniverse.getPreferredConfiguration();
        Canvas3D c = new Canvas3D(config);
        add("Center",c);
        c.addKeyListener(this);
        c.setSize(500,500);
        timer = new Timer(100,this);
        timer.start();
        BranchGroup scene = createSceneGraph();
        BranchGroup scene2 = createSceneGraph2();
        SimpleUniverse u = new SimpleUniverse(c);
        u.getViewingPlatform().setNominalViewingTransform();
        u.addBranchGraph(scene);
        u.addBranchGraph(scene2);
        for(float i = 0; i < .10f; i++){
            x = 1.5f;
            dx = -.05f;
        }
    }

    public void keyPressed(KeyEvent e){
        if(e.getKeyChar() == 'd'){
            xloc = xloc + .1f;
        }

        if(e.getKeyChar() == 'a'){
            xloc = xloc - .1f;
        }
    }

    public void keyReleased(KeyEvent e){

    }

    public void keyTyped(KeyEvent e){

    }

    public void actionPerformed(ActionEvent e){
        height += .1f * sign;
        if(Math.abs(height * 2) >= 1)
            sign = -1.0f * sign;
        if(height < -.4f){
          trans.setScale(new Vector3d(1.0,.8,1.0));
        }else{
          trans.setScale(new Vector3d(1.0,1.0,1.0));
        }
        trans.setTranslation(new Vector3f(xloc,height - .15f,0.0f));
        objTrans.setTransform(trans);
        if(height < -.4f){
          trans.setScale(new Vector3d(1.0,1.0,1.0));
        }
        trans.setTranslation(new Vector3f(x += dx,-.7f,0.0f));
        objTrans2.setTransform(trans);
    }

    public static void main(String[] args){
        System.out.println("Program Started");
        PAPITest pt = new PAPITest();
        pt.addKeyListener(pt);
    }
}

Edit: Now I have added something that I think would work if I could make it more accurate. I added these two methods:

public void getSpherePosition(){
        positionX = (int) xloc;
        positionY = (int) height;
        position = positionX + positionY;
    }

    public void getSphere2Position(){
        positionX2 = (int) x;
        positionY2 = (int) -.7f;
        position2 = positionX2 + positionY2;
    }

and I added this in the actionPerformed method:

        getSpherePosition();
        getSphere2Position();
        if(position == position2){
            System.out.println("It Worked");
        }

It kinda works because the It Worked text only show up when the player ball is near the enemy ball, it also show up when I first start the program.

Is there a better way to do it on? If so how do I do it on that way? And how can I make my way be more accurate and not show the text directly when I start the program?

I know that it becomess unaccurate because I just plused the three variables together, so position can equals position2 even if the playe and enemy don't touch each other, but I can't figure out how to do it in a different way.

Answer 1

I am sorry for the time it has taken to get back to you. Java3d has built in methods that seem to have been buried in to the darkest of all knowledge. I found a method of collision detection that is crude, but works.

Here is a simple snip it for a method that can be called upon to give collision.

import java.util.Enumeration;
import javax.media.j3d.Behavior;
import javax.media.j3d.Bounds;
import javax.media.j3d.Node;
import javax.media.j3d.Shape3D;
import javax.media.j3d.WakeupCriterion;
import javax.media.j3d.WakeupOnCollisionEntry;
import javax.media.j3d.WakeupOnCollisionExit;
import javax.media.j3d.WakeupOnCollisionMovement;
import javax.media.j3d.WakeupOr;



/**
 *
 * @author sawyera.2016
 */
 public class Coll extends Behavior {
 /** The separate criteria used to wake up this beahvior. */
 protected WakeupCriterion[] theCriteria;

 /** The OR of the separate criteria. */
 protected WakeupOr oredCriteria;

 /** The shape that is watched for collision. */
  protected Shape3D collidingShape;

  /**
    * @param theShape
   *            Shape3D that is to be watched for collisions.
   * @param theBounds
   *            Bounds that define the active region for this behaviour
   */
  public Coll(Shape3D theShape, Bounds theBounds) {
   collidingShape = theShape;
   setSchedulingBounds(theBounds);
    }


  /**
   * This creates an entry, exit and movement collision criteria. These are
   * then OR'ed together, and the wake up condition set to the result.
   */
  public void initialize() {
    theCriteria = new WakeupCriterion[3];
    theCriteria[0] = new WakeupOnCollisionEntry(collidingShape);
    theCriteria[1] = new WakeupOnCollisionExit(collidingShape);
    theCriteria[2] = new WakeupOnCollisionMovement(collidingShape);
    oredCriteria = new WakeupOr(theCriteria);
    wakeupOn(oredCriteria);
  }

  /**
   * Where the work is done in this class. A message is printed out using the
   * userData of the object collided with. The wake up condition is then set
   * to the OR'ed criterion again.
   */
  public void processStimulus(Enumeration criteria) {
    WakeupCriterion theCriterion = (WakeupCriterion) criteria.nextElement();
    if (theCriterion instanceof WakeupOnCollisionEntry) {
      Node theLeaf = ((WakeupOnCollisionEntry) theCriterion)
          .getTriggeringPath().getObject();
      System.out.println("Collided with " + theLeaf.getUserData());
    } else if (theCriterion instanceof WakeupOnCollisionExit) {
      Node theLeaf = ((WakeupOnCollisionExit) theCriterion)
          .getTriggeringPath().getObject();
      System.out.println("Stopped colliding with  "
      + theLeaf.getUserData());
    } else {
      Node theLeaf = ((WakeupOnCollisionMovement) theCriterion)
      .getTriggeringPath().getObject();
  System.out.println("Moved whilst colliding with "
      + theLeaf.getUserData());
    }
    wakeupOn(oredCriteria);
  }
}

I cannot take full credit for this, i did get some information about it from the web however i made this version from a 1.2 version of java3d.