In case it matters and you are interested, Lemur has scene picking build in. You just add listeners to whatever node/geometry you like and you will get notified.
Deeper old example here: Lemur Gems #3 : Scene picking
…but the short version is:
MouseEventControl.addListenersToSpatial(node, new DefaultMouseListener() {
protected void click( MouseButtonEvent event, Spatial target, Spatial capture ) {
// do the stuff
}
});
Then whenever the mouse clicks on ‘node’, the click method is called.
Edit: also note that you can use the scene picking even if you don’t use the rest of Lemur for your UI or anything.