private Geometry makeFloor() {
    Box box = new Box(15, .2f, 15);
    Geometry floor = new Geometry("the Floor", box);
    floor.setLocalTranslation(0, -4, -5);
    Material mat1 = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
    mat1.setColor("Color", ColorRGBA.Gray);
    floor.setMaterial(mat1);
    return floor;
  }
A floor to show that the "shot" can go through several objects.
jme3-examples/src/main/java/jme3test/helloworld/HelloPicking.java