offScreen = true;
offScreenCanvas = GLDrawableFactory.getFactory().createGLPbuffer(cap, new DefaultGLCapabilitiesChooser(), width, height, null);
offScreenCanvas.addGLEventListener( glEventListener );

outputFile = new File( dumpname );
// this causes all the events to fire
 // Also screen capture is done inside the Display loop.
offScreenCanvas.display();

// tidy up the event listener - upto you to do this
offScreenCanvas.removeGLEventListener(this);
offScreenCanvas.destroy();

if ( offScreen ) {
  try {
       Screenshot.writeToFile( outputFile, screenDim.width, screenDim.height );
  }
  catch( IOException ioe ) {
       System.err.println( "Error Creating File: " + ioe.getMessage() );
  }
}

GLCapabilities cap = new GLCapabilities();
cap.setDoubleBuffered(false);
offScreenCanvas = GLDrawableFactory.getFactory().createGLPbuffer(cap, width, height, null);

  public synchronized void dumpImage(final int val, final int width, final int height, final String dumpname)
  {
    if (!GLDrawableFactory.getFactory().canCreateGLPbuffer()) {
      System.err.println("Error: canvas does not support off-screen drawables.");
      return;
    }

    boolean oldOffScreen = offScreen;

    offScreen = true;

    Dimension oldSize = new Dimension(screenDim);
    java.awt.Point oldScreenCorner = new java.awt.Point(screenCorner);

    screenDim.height = height;
    screenDim.width = width;

    screenCorner.x = 0;
    screenCorner.y = 0;

    GLCapabilities cap = new GLCapabilities();

    setCapabilities(cap, false, true);

    // Creates an offscreen canvas with an empty context that gets created later.
    final GLPbuffer offScreenCanvas = GLDrawableFactory.getFactory().createGLPbuffer(cap, width, height, null);

  private final void setCapabilities(GLCapabilities cap, final boolean stereo, final boolean offScreen) {
    cap.setDepthBits(24);
    // 24 bit colour:
    cap.setRedBits(8);
    cap.setBlueBits(8);
    cap.setGreenBits(8);
    cap.setAlphaBits(8);

    cap.setAccumRedBits(16);
    cap.setAccumGreenBits(16);
    cap.setAccumBlueBits(16);
    cap.setAccumAlphaBits(16);

    // we only need one stencil bit. But we'll see how many we get...
    cap.setStencilBits(8);

    if (offScreen) // Off screen renderring
      cap.setDoubleBuffered(false);
    else {
      cap.setDoubleBuffered(true);
      // Uncomment this for stereo visual
      if(stereo)
        cap.setStereo(true);
    }
  }