When you use M3G graphics for creating 3D games in J2ME, you need to find the collision between objects. RayIntersection class gives the required functionality.

But in most cases, rayIntersection method works only with the Pick method where you specify your camera.

rayIntersection.getIntersected() method gives you the node to which the Ray is intersected and you can also get the distance between the camera and the object. With these information you can determine whether the camera has collided with a 3D object like wall and take appropriate actions such as bounce back or restrict movements.