Posted by Nosezeichen on Oct 31, 2014; 1:32pm
URL: https://forum.jogamp.org/Offscreen-Rendering-with-GLCanvas-which-wasn-t-created-with-this-capability-tp4033474.html

Hi,

I'm struggling with a third Party JOGL-Application wich I want to integrate into my own jMonkeyEngine application.

Basically I want to enable offscreen-rendering with a GLCanvas wich was created without this capability. Is it somehow possible to change capabilities after creating a Canvas ? Or use some other hackish methods to render it anyhow ?

I had to implement an abstract method of the 3rd-Party app:

public void embedInContainer(Component jacanvas) {
        // jacanvas is in fact an Object of type javax.media.opengl.awt.GLCanvas

        /* Initialization */
        // create JPanel and configure it
        javax.swing.JPanel panel;
        panel = new JPanel(new BorderLayout());
        panel.setBorder(BorderFactory.createEmptyBorder(0, 0, 0, 0));
        panel.setPreferredSize(size);
        panel.setMinimumSize(size);
        panel.setMaximumSize(size);
        panel.setSize(size);
        panel.setBounds(0, 0, size.width, size.height);
        panel.setBackground(Color.red);
        // Add the GLCanvas which is in the comp variable to the JPanel
        panel.add(comp, BorderLayout.CENTER);
        panel.setVisible(true);

        // create JFrame and configure it
        javax.swing.JFrame frame;
        frame = new JFrame();
        frame.setBackground(Color.WHITE);
        frame.setUndecorated(true);
        frame.setPreferredSize(size);
        frame.setMinimumSize(size);
        frame.setMaximumSize(size);
        frame.setSize(size);
        frame.setBounds(0, 0, size.width, size.height);
        // Add the panel to the frame
        frame.getContentPane().add(panel);
        frame.pack();
        frame.setVisible(true); // I can see the ouptut and can copy it to my buffer via glReadPixels
       
        frame.setVisible(false); // I can't see output and buffer holds a black image (like I expected, because it's not an offscreen renderable)
}

When putting the GLCanvas to a visible frame the output of the 3rd-Party app is shown. When setting the frame invisible the GLCanvas doesnt become rendered at all (reading the rendered output into my buffer with glReadPixels delivers a black image).

The jframe and jpanel stuff is just to see if it works at all. I dont want to use them. I want to put the output of the 3rd party jogl app into a buffer so that i can use it as a texture later on.

I've allready posted my Problem in the jme-forum but no one seems to can help me.
Here is the Post with a code example and a description: http://hub.jmonkeyengine.org/forum/topic/how-to-render-a-glcanvas-inside-jme3/

Thank you!
Nosezeichen