Do you mean you want two applets on the same Web page, communicating in some way?

I have no experience in the field, but I think you should be more specific in your question. What have you tried to do, and how it failed?

http://forum.processing.org/topic/multiple-windows

Hi guys thanks a lot for your answers.
What I am trying to do is to have both windows in 3d with peasyCam running on both and drawing 3d stuff on both. It is that I would like to know if it is possible to do and how. I don't want to have just sliders drawn on the second window. And because my code is quiet complex by now I wanted to know as well whether its possible to call classes stuff to the second applet. Does anybody ever come across this?
many thanks,
buzz

It is possible to create two separate windows, in fact as many windows as you like. I had once created a program which had a single parent window, and it had multiple child windows, all running sketches in parallel (maybe on separate threads) and they exchanged data among each other. I implemented it using java frames and embedded my applet into the frame. Is this similar to what you want to achieve? Or are you wanting to split your output in two separate windows? I don't think I know about the latter.

So far, we haven't seen even a simple/simplified example of what you try to do. I believe you must have two applets, ie. two sketches, two jars (at least), put independently on a Web page, that communicate in some way, eg. via JavaScript, or some other mean. You need to use RPC or some other mean. I don't think you can send direct invocations of functions or class' methods to the other applet. Although I can be wrong, as I wrote I have no experience in the field. And I have seen little experimentations in the field (but you can search both forums via the Processing site).
The advices above are about having a second frame, ie. an independent window, outside of the browser, which is different.

Here's a simple demo demonstrating the concept I'd used: