Question

I’m currently experimenting with JOGL, and I ran into a problem which is really new to me. After starting the program, I see a blank window. After resize, I can normally see the content of it or if I do a minimise/restore. I suppose there is something with the events. The init() isn’t called after the window created, but after the first trigger with resize or minimise.

Here is the code what I’m using for creating a window and setting up OpenGL:

package com.cogwheel.framework.graphics;

import java.awt.BorderLayout;

import javax.media.opengl.GL;
import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.awt.*;
import javax.swing.JFrame;

import com.cogwheel.framework.init.CWGPreferences;
import com.cogwheel.framework.util.CWGDebug;
import com.jogamp.opengl.util.Animator;

public class CWGOpenGLScreen extends JFrame implements GLEventListener {
private static final String TAG = "CWGOpenGLScreen";

private GLCanvas mCanvas;
private long fpsLast = System.currentTimeMillis();

public CWGOpenGLScreen(){
    this.setTitle(CWGPreferences.WINDOW_NAME);
    this.setSize(CWGPreferences.WINDOW_SIZE);
    this.setLayout(new BorderLayout());
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    ///this.setResizable(false);
    this.setVisible(true);

    CWGDebug.info(TAG, "Window created!");

    CWGSetupGL();
}
private void CWGSetupGL(){
    GLCapabilities mCaps = new GLCapabilities(null);
    mCaps.setHardwareAccelerated(true);
    mCaps.setDoubleBuffered(true);

    mCanvas = new GLCanvas(mCaps);
    mCanvas.addGLEventListener(this);

    this.add(mCanvas, BorderLayout.CENTER);

    Animator animator = new Animator(mCanvas);
    animator.start();
}

public void CWGDrawScene(GLAutoDrawable drawable)
{
    CWGCalculateFPS();

    GL2 gl = drawable.getGL().getGL2();
    gl.glClear(GL.GL_COLOR_BUFFER_BIT);
    gl.glLoadIdentity();


    gl.glBegin(GL.GL_TRIANGLES);
        gl.glColor3f(1.0f, 0.0f, 0.0f);
        gl.glVertex3f(1.0f / 5 , 0.0f, 0.0f);

        gl.glColor3f(0.0f, 1.0f, 0.0f);
        gl.glVertex3f(1.0f / 5, 1.0f / 5, 0.0f);

        gl.glColor3f(0.0f, 0.0f, 1.0f);
        gl.glVertex3f(0.0f, 1.0f / 5, 1.0f / 5);
    gl.glEnd();
    gl.glFlush();
}

public void CWGCalculateFPS(){
    this.setTitle(CWGPreferences.WINDOW_NAME + " [" + 1000 / (System.currentTimeMillis() - fpsLast) + "]");
    fpsLast = System.currentTimeMillis();
}

public void init(GLAutoDrawable drawable){
        /*GL2 gl = drawable.getGL().getGL2();

        gl.glClearColor(0, 0, 0, 0);
        gl.glMatrixMode(GL2.GL_PROJECTION);
        gl.glLoadIdentity();
        gl.glOrtho(0, 1, 0, 1, -1, 1);
        */
        CWGDebug.info(TAG, "Init called!");
}
public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height){}
public void displayChanged(GLAutoDrawable drawable, boolean modeChanged, boolean deviceChanged){}
public void display(GLAutoDrawable drawable){ CWGDrawScene(drawable); }
public void dispose(GLAutoDrawable drawable){}

}

Code quality is poor, I know, had no time to cleanup yet. Sorry for it.

Edit: got the problem, JFrame should not be shown until the GLEventListener is not initialised.

Answer 1

I’ve found your error (it has nothng to do with eclipse) : you should have set up the viewport (call to glViewport) whenever the canvas is resized => so you call glViewport(x,y, widht, height) in the reshape() method of the GLEventListener. So that OpenGL always knows where to draw scene, and not just when resizing frame.

Also, don’t forget to setup screen (call to CWGSetupGL()) before showing it (otherwise you will still have the same problem, but only for a little time).

Here the modified code (I’ve removed calls to CWGDebug.info as you did not provide this class, but you can put them back) :

package com.cogwheel.framework.graphics;

import java.awt.BorderLayout;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

import javax.media.opengl.GL;
import javax.media.opengl.GL2;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCapabilities;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.awt.GLCanvas;
import javax.swing.JFrame;

import com.jogamp.opengl.util.Animator;

public class CWGOpenGLScreen extends JFrame implements GLEventListener {

    public static void main(String[] args) {
        new CWGOpenGLScreen().setVisible(true);
    }

private static final long serialVersionUID = 635066680731362587L;

private static final String TAG = "CWGOpenGLScreen";

private GLCanvas mCanvas;
private long fpsLast = System.currentTimeMillis();

public CWGOpenGLScreen(){
    this.setTitle(TAG);
    this.setSize(640,480);
    this.setLayout(new BorderLayout());
    this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    ///this.setResizable(false);

    CWGSetupGL();
    this.setVisible(true);

//    CWGDebug.info(TAG, "Window created!");
}
private void CWGSetupGL(){
    GLCapabilities mCaps = new GLCapabilities(null);
    mCaps.setHardwareAccelerated(true);
    mCaps.setDoubleBuffered(true);

    mCanvas = new GLCanvas(mCaps);
    mCanvas.addGLEventListener(this);

    this.add(mCanvas, BorderLayout.CENTER);

    final Animator animator = new Animator(mCanvas);
    animator.start();

    addWindowListener(new WindowAdapter() {

        @Override
        public void windowClosing(WindowEvent e) {
            animator.stop();
            System.exit(0);
        }



    });
}

public void CWGDrawScene(GLAutoDrawable drawable)
{
    CWGCalculateFPS();

    GL2 gl = drawable.getGL().getGL2();
    gl.glClear(GL.GL_COLOR_BUFFER_BIT);
    gl.glLoadIdentity();


    gl.glBegin(GL.GL_TRIANGLES);
        gl.glColor3f(1.0f, 0.0f, 0.0f);
        gl.glVertex3f(1.0f / 5 , 0.0f, 0.0f);

        gl.glColor3f(0.0f, 1.0f, 0.0f);
        gl.glVertex3f(1.0f / 5, 1.0f / 5, 0.0f);

        gl.glColor3f(0.0f, 0.0f, 1.0f);
        gl.glVertex3f(0.0f, 1.0f / 5, 1.0f / 5);
    gl.glEnd();
    gl.glFlush();
}

public void CWGCalculateFPS(){
    this.setTitle(TAG + " [" + 1000 / (System.currentTimeMillis() - fpsLast) + "]");
    fpsLast = System.currentTimeMillis();
}

public void init(GLAutoDrawable drawable){
        /*GL2 gl = drawable.getGL().getGL2();

        gl.glClearColor(0, 0, 0, 0);
        gl.glMatrixMode(GL2.GL_PROJECTION);
        gl.glLoadIdentity();
        gl.glOrtho(0, 1, 0, 1, -1, 1);
        */
//        CWGDebug.info(TAG, "Init called!");
}
public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height){
    GL2 gl = drawable.getGL().getGL2();
    gl.glViewport(x, y, width, height);
}
//public void displayChanged(GLAutoDrawable drawable, boolean modeChanged, boolean deviceChanged){}
public void display(GLAutoDrawable drawable){ CWGDrawScene(drawable); }
public void dispose(GLAutoDrawable drawable){}
}

Regards 🙂

Edit : apologizes, I haven’t seen you replied yourself to your own question, by an edit.
Anyway, I still think you’d better call glViewport in reshape() method.