public void addProcessor(SceneProcessor processor) {
        if (processor == null) {
            throw new IllegalArgumentException("Processor cannot be null.");
        }
        processors.add(processor);
    }
Adds a {@link SceneProcessor} to this ViewPort.

<p>SceneProcessors that are added to the ViewPort will be notified
of events as the ViewPort is being rendered by the {@link RenderManager}.

@param processor The processor to add

@see SceneProcessor
jme3-core/src/main/java/com/jme3/renderer/ViewPort.java