[JAVA3D] Collision Detection

Dean Keeler Mon, 17 Jan 2000 06:03:04 -0800

Hi All,

I am trying to write a collision detection routine. I have followed the examples in the "Ready-to-Run Java 3D" book and also from mail archive from Tony Burrows. I have been unable to get it to work. Whenever I try to use the collision detection routine it hangs the process and I have to go into Task Manager on WinNT and shut down the task. I have also looked at the "TickTockCollision" Example and have not been able to get any farther. I am reading in a VRML file with named nodes and am setting collision detection on those nodes. Can anyone help? Please.

Also, do I set the collision detection on the node that I am moving or on all the other nodes? That part was not quite clear to me.

Below is my collision detector class:

import java.util.*;
import javax.media.j3d.*;
import javax.vecmath.*;
import com.sun.j3d.utils.geometry.Primitive;

public class CollisionDetector extends Behavior
{
private boolean      inCollision = false;
private WakeupOnCollisionEntry  wEnter;
private WakeupOnCollisionExit  wExit;
private TransformGroup    targetObject;

public CollisionDetector(TransformGroup obj)
{
  inCollision = false;
  targetObject = obj;
  System.out.println("Collider Created...");
}

public void initialize()
{
  wEnter = new WakeupOnCollisionEntry(targetObject);
  wExit = new WakeupOnCollisionExit(targetObject);
  wakeupOn(wEnter);
  System.out.println("Collider Initialized...");
}

public void processStimulus(Enumeration criteria)
{
  inCollision = !inCollision;
  if (inCollision)
  {
   System.out.println("Collision Detected ...");
   wakeupOn(wExit);
  }
  else
  {
   wakeupOn(wEnter);
  }
}
}

Below is where I instantiate the collision detector class:

  file://Load in the Fixture VRML file
  Scene  scene = null;
  VrmlLoader loader = new VrmlLoader();
  try
  {
   URL loadURL = new URL(this.getCodeBase(),fixtureFile);
   try
   {
    System.out.println("loadURL = " + loadURL.toString());
    scene = loader.load(loadURL);
   }
   catch (Exception e)
   {
    System.out.println("Exception loading URL:" + e);
   }
  }
  catch (MalformedURLException badURL)
  {
   file://location may be a path name
   try
   {
    scene = loader.load(fixtureFile);
   }
   catch (Exception e)
   {
    System.out.println("Exception loading file from path: " + e.getMessage());
   }
  }
  if (scene != null)
  {
   fixture_BG = scene.getSceneGroup();
   fixture_BG.setCapability(BranchGroup.ALLOW_DETACH);
   fixture_BG.setCapability(BranchGroup.ALLOW_BOUNDS_READ);
   fixture_BG.setCapability(BranchGroup.ALLOW_BOUNDS_WRITE);

   file://Add the machine to the transform group
   fixture_TG.addChild(fixture_BG);

   file://Set capabilities on all named nodes
   TransformGroup nodeGroup = new TransformGroup();
   String   nodeID;
   Hashtable allNodes = scene.getNamedObjects();
   if (!allNodes.isEmpty())
   {
    Enumeration e = allNodes.keys();
    if (e.hasMoreElements())
    {
     do
     {
      nodeID = (String)e.nextElement();
      if (allNodes.get(nodeID).getClass() == nodeGroup.getClass())
      {
       System.out.println("NodeID = " + nodeID);

        file://Get the node group (transformaion group)
        nodeGroup = (TransformGroup)allNodes.get(nodeID);

        file://Set node group capabilities
        nodeGroup.setCapability(TransformGroup.ALLOW_BOUNDS_READ);
        nodeGroup.setCapability(TransformGroup.ALLOW_TRANSFORM_READ);
        nodeGroup.setCapability(TransformGroup.ALLOW_TRANSFORM_WRITE);
        nodeGroup.setCapability(TransformGroup.ALLOW_COLLISION_BOUNDS_READ);
        nodeGroup.setCapability(TransformGroup.ALLOW_COLLISION_BOUNDS_WRITE);
        nodeGroup.setCapability(TransformGroup.ALLOW_COLLIDABLE_READ);
        nodeGroup.setCapability(TransformGroup.ALLOW_COLLIDABLE_WRITE);


        if (nodeID.equals("Part"))
        {
         file://Create the collision detector for this node.
         CollisionDetector cd = new CollisionDetector(nodeGroup);
//         cd.setSchedulingBounds(nodeBounds);
         nodeGroup.addChild(cd);
         detectors.put((String)nodeID,(CollisionDetector)cd);
        }
        System.out.println("number of children = " + nodeGroup.numChildren());

        file://Set collidable status for the node group to true;
        nodeGroup.setCollidable(true);

        validNodes.put((String)nodeID,(TransformGroup)nodeGroup);
      }
     }
     while (e.hasMoreElements());
    }
    allNodes.clear();
   }
  }

  file://Add the scene to the scene graph to the locale
  locale.addBranchGraph(world_BG);

  file://now that the scene group is "live" calculate the new bounds
  BoundingSphere sceneBounds = (BoundingSphere)world_BG.getBounds();

  file://set up a view point to include the bounds
  SetViewPoint(sceneBounds);



  file://Now that a scene bounds has been established, Set the scheduling bounds for each of the collision detectors created.
  CollisionDetector temp_CD;
  TransformGroup  temp_Node;

  if (!validNodes.isEmpty())
  {
   String  nodeID;
   Enumeration e = validNodes.keys();
   if (e.hasMoreElements())
   {
    do
    {
     nodeID = (String)e.nextElement();

     temp_Node = (TransformGroup) validNodes.get(nodeID);
     temp_Node.setCollisionBounds(temp_Node.getBounds());
     validNodes.put((String)nodeID, (TransformGroup)temp_Node);

     if (detectors.contains(nodeID))
     {
      temp_CD = (CollisionDetector) detectors.get(nodeID);
      temp_CD.setSchedulingBounds(temp_Node.getBounds());
      System.out.println("temp_Node = " + temp_Node.getBounds());
     }
    }
    while (e.hasMoreElements());
   }
   detectors.clear();
  }

Thanks for any suggestion that you can give me.

Dean

[JAVA3D] Collision Detection

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