private void initMark() {
    Sphere sphere = new Sphere(30, 30, 0.2f);
    mark = new Geometry("BOOM!", sphere);
    Material mark_mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
    mark_mat.setColor("Color", ColorRGBA.Red);
    mark.setMaterial(mark_mat);
  }
A red ball that marks the last spot that was "hit" by the "shot".
jme3-examples/src/main/java/jme3test/helloworld/HelloPicking.java