Can you post the code? I believe there is a thread on this forum that can help.

Thanks for asking me to send some code: For demonstration purposes I simplified my code until I had accidentally removed the (trivial) bug. ......Apparently I need to get my debugging practices straight! Anyway, everything works fine now.

  But for all those who are interested in using Swing and Processing together using Java, I'll explain how I did it:

In the following, substitute the 'myOpenGLFolder' for the name of your processing opengl library folder and 'myFileName' for the name of your compiled java file.

in the terminal, type

1. java -Djava.library.path="myOpenGLFolder" myFileName

or in Netbeans, go to project properties, go to 'run', and add this to the VM Options section:

1. -Djava.library.path="myOpenGLFolder" myFileName

and I don't know Eclipse but there must be some run configuration where you can add this same line.

And of course, don't forget to add the OpenGL library to your project. This is my Java (not Processing!) code:

1. import java.awt.*;
   import javax.swing.*;
   import processing.core.*;
   
   public class ProcessingAndSwing extends JApplet {
   
       @Override
       public void init()
       {
           setSize(600,400);
           SomePApplet audio = new SomePApplet();
           getContentPane().setLayout(new BorderLayout());
   
           getContentPane().add(audio, BorderLayout.CENTER);
           audio.init();
   
           JPanel j = new JPanel();
           j.setBackground(Color.red);
           j.add(new JButton("A swing component!"));
           getContentPane().add(j, BorderLayout.WEST);
       }
   
       public class SomePApplet extends PApplet
       {
           float rotationY=0, rotationZ=0;
   
           @Override
           public void setup()
           {
               size(getWidth(),getHeight(),OPENGL);
           }
   
           @Override
           public void draw()
           {
               background(0);
               rotationY+=0.05f;
               rotationZ+=0.08f;
               translate(200,200);
               rotateY(rotationY);
               rotateZ(rotationZ);
               stroke(255,0,0);
               fill(255,255,0);
               strokeWeight(2);
               box(80);
               translate(100,100);
               box(80);
              
           }
       }
   }

Here is a thread on switching renderers on the fly

http://forum.processing.org/topic/switching-renderers-on-the-fly

It has its limitations however.

You cannot close the main sketch. If that is closed all subsequent sketches are closed, however the child sketches can be closed at any time.

The child sketches can be resized however, you should write your own code to refesh each based on the width and size variants. I find if you localize w and h variables and manipulate them individually, when the redraw() command is issued that makes it easier.

If you want me to post any snippets you can indicate such. There is another thread. I will post it when I find it.