Regarding (1) I read it  here in the processing devel site that one should register the mouse events rather than one's class implementing MouseListener. However nothing is said about the mouse wheel and I just assumed that the same goes for it (that it was discouraged) and that I was missing something :) Thanks for the clarification I left my code as it is and till now nothing seems to be broken ;)

1. public void mouseEvent(MouseEvent event) {
2.     if (event instanceof MouseWheelEvent) {
3.         // handle your mouse wheel stuff here...
4.     }
5. }
   

1. public void mouseEvent(MouseEvent event) {
2. case MouseEvent.MOUSE_WHEEL: 
3.   this.mouseWheelMoved((MouseWheelEvent)event);
   break;

1. import remixlab.proscene.*;
   import napplet.*;
   
   NAppletManager nappletManager;
   
   void setup() {
     size(640, 720, P3D);
     nappletManager = new NAppletManager(this);
     nappletManager.createNApplet("MainViewer", 0, 0);
     nappletManager.createNApplet("AuxiliarViewer", 0, 360);
   }
   
   void draw() {
     background(50);
   }
   

1. public class MainViewer extends NApplet {
     Scene scene;
    
     void setup() {
       size(640, 360, P3D);
       scene = new Scene(this);
     }
    
     void draw() {
       noStroke();
       fill(0, 255, 0);
       sphere(40);
     }   
   }

1. public class AuxiliarViewer extends NApplet {
     Scene scene;
    
     void setup() {
       size(640, 360, P3D);
       scene = new Scene(this);
     }
    
     void draw() {
       noStroke();
       fill(0, 255, 0);
       box(40);
     }
   }

1.       p.frame.addMouseWheelListener(
2.         new MouseWheelListener() {
3.           void mouseWheelMoved(MouseWheelEvent e) {
4.               println(e.getWheelRotation());
5.           }
6.         }
7.       ); //an abstract mouse wheel listener class instance argument
8. //http://processing.org/discourse/yabb2/YaBB.pl?num=1183986357/1 

1. Proscene registers at the papplet the following methods: pre(), draw(), keyEvent() and mouseEvent(); for example, by calling parent.registerPre(this) and then implementing the pre() method (and so on with the rest of them).
2. To handle the mouse wheel, proscene implements the MouseWheelListener interface and then calls parent.addMouseWheelListener(this), which adds the listener at the papplet (not at the papplet's frame as suggested above).

1. java.lang.reflect.InvocationTargetException
2.     at sun.reflect.GeneratedMethodAccessor3.invoke(Unknown Source)
3.     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
4.     at java.lang.reflect.Method.invoke(Method.java:597)
5.     at processing.core.PApplet$RegisteredMethods.handle(Unknown Source)
6.     at processing.core.PApplet.handleMouseEvent(Unknown Source)
7.     at processing.core.PApplet.dequeueMouseEvents(Unknown Source)
8.     at processing.core.PApplet.handleDraw(Unknown Source)
9.     at napplet.NApplet.handleDraw(Unknown Source)
10.     at napplet.NApplet.runFrame(Unknown Source)
11.     at napplet.NAppletManager.draw(Unknown Source)
12.     at sun.reflect.GeneratedMethodAccessor6.invoke(Unknown Source)
13.     at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
14.     at java.lang.reflect.Method.invoke(Method.java:597)
15.     at processing.core.PApplet$RegisteredMethods.handle(Unknown Source)
16.     at processing.core.PApplet$RegisteredMethods.handle(Unknown Source)
17.     at processing.core.PApplet.handleDraw(Unknown Source)
18.     at processing.core.PApplet.run(Unknown Source)
19.     at java.lang.Thread.run(Thread.java:619)
20. Caused by: java.lang.NullPointerException
21.     at remixlab.proscene.InteractiveCameraFrame.mouseMoveEvent(InteractiveCameraFrame.java:257)
22.     at remixlab.proscene.Scene.mouseDragged(Scene.java:2096)
23.     at remixlab.proscene.Scene.mouseEvent(Scene.java:1933)
24.     ... 18 more