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I'm working on a java project; "car game" and I want to detect collisions between the car and any object ("Node"); such as cones on the road.

Similar to this tutorial; http://jmonkeyengine.org/wiki/doku.php/jme3:beginner:hello_picking

The tutorial shows finding the intersection between a ray and the node which has the boxes attached to it. I want to replace the ray with the car chassis for intersection detection.

Richard Tingle
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Mostafa Abd El Razek
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1 Answers1

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Assume you have two collidables a and b and want to detect collisions between them. The collision parties can be Geometries, Nodes with Geometries attached (including the rootNode), Planes, Quads, Lines, or Rays. An important restriction is that you can only collide geometry vs bounding volumes or rays. (This means for example that a must be of Type Node or Geometry and b respectively of Type BoundingBox, BoundingSphere or Ray.)

The interface com.jme3.collision.Collidable declares one method that returns how many collisions were found between two Collidables: collideWith(Collidable other, CollisionResults results).

Code Sample:

// Calculate detection results
  CollisionResults results = new CollisionResults();
  a.collideWith(b, results);
  System.out.println("Number of Collisions between" + 
      a.getName()+ " and " + b.getName() + ": " + results.size());
  // Use the results
  if (results.size() > 0) {
    // how to react when a collision was detected
    CollisionResult closest  = results.getClosestCollision();
    System.out.println("What was hit? " + closest.getGeometry().getName() );
    System.out.println("Where was it hit? " + closest.getContactPoint() );
    System.out.println("Distance? " + closest.getDistance() );
  } else {
    // how to react when no collision occured
  }
}

I think you need also to read this tutorial

http://hub.jmonkeyengine.org/wiki/doku.php/jme3:advanced:collision_and_intersection

Hope this helps.

V-Q-A NGUYEN
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    what they don't tell you is that you can use getWorldBound get the proper bounding box of a spatial. The tutorial sais somthing about setBound, but that does not work because the transforms are not applied to that new bound, so it will be scale one at 0,0,0 wit no rotation. Use getWorldBound insteat of setting a new one and updating it. It took me too long to figure that out – Jappie Kerk Jun 29 '14 at 14:59
  • @JappieKerk I am trying to find a way to spawn physics objects in a way they are not placed over other objects; I want to check if there is an object there before enabling the new one physics; I guess getWorldBound() may do the trick? – Aquarius Power Dec 24 '14 at 15:55