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OpenGL Weird Error with JOGL

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I apologize in advance if this is the wrong section of the forum to post this in.

So I'm trying to get a grip with the various methods in JOGL and have been reading a couple of texts on how to use it effectively. This error popped up when I copied word for word one of the first examples in a textbook I was using. The code is as follows:

[code]

import java.awt.*;
import javax.swing.*;
import javax.media.opengl.*; // If thise does not work, try net.java.games.jogl.*, or get the newest version of JOGL.

import com.sun.opengl.util.Animator;


public class JOGLApp extends JFrame {

// Causes our JOGL app to be animated- that is, it keeps calling display()
static Animator anim = null;

public static void main(String[] args) {
final JOGLApp app = new JOGLApp();

// Creates the window in another thread
SwingUtilities.invokeLater (
new Runnable() {
public void run() {
app.setVisible(true);
}
}
);
}

public JOGLApp() {
// Set the JFrame title
super("JOGL Application");

// Kill the process when the JFrame is closed
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

GLCanvas glCanvas = new GLCanvas(new GLCapabilities());
glCanvas.addGLEventListener(new GameGLEventListener());

// Add the GLCanvas just like we would any Component
getContentPane().add(glCanvas, BorderLayout.CENTER);
setSize(500, 300);

centerWindow(this);
}

public void centerWindow(Component frame){
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
Dimension frameSize = frame.getSize();

if(frameSize.width > screenSize.width){
frameSize.width = screenSize.width;
}
if(frameSize.height > screenSize.height){
frameSize.height = screenSize.height;
}

frame.setLocation(
(screenSize.width - frameSize.width) >> 1,
(screenSize.height - frameSize.height) >> 1
);

}

}
[/code]

[code]

import javax.media.opengl.*; // If thise does not work, try net.java.games.jogl.*, or get the newest version of JOGL.
import javax.media.opengl.glu.GLU;

public class GameGLEventListener implements GLEventListener {
float rotate = 0;

// Only put stuff here that should happen once, at the beginning of the program
public void init(GLAutoDrawable gld) {
GL gl = gld.getGL();
GLU glu = new GLU();

gl.glClearColor(0, 0, 0, 1);

gl.glViewport(0, 0, 500, 300);
gl.glMatrixMode(GL.GL_PROJECTION);
gl.glLoadIdentity();
glu.gluOrtho2D(0, 500, 0, 300);
}

public void display(GLAutoDrawable gld) {
float red = 0;
float green = 0;
float blue = 0;

GL gl = gld.getGL();

gl.glClear(GL.GL_COLOR_BUFFER_BIT);

gl.glPointSize(5);

for(int i=0; i<50; i++){

red -= 0.09;
green -= 0.12;
blue -= 0.15;

if(red < 0.15) red = 1;
if(green < 0.15) green = 1;
if(blue < 0.15) blue = 1;

gl.glColor3f(red, green, blue);

gl.glBegin(GL.GL_POINTS);
gl.glVertex2i(i*10, 150);
gl.glEnd();
}
}

// This function is only called when the window is reshaped. You probably won't need this.
public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) {}

// This function is only called when the display settings are changed. Again, not often used.
public void displayChanged(GLAutoDrawable drawable, boolean a, boolean B) {}
}
[/code]


What happens is that the window displays on me screen, flashes the image quickly then becomes a black window. However, if I resize the window, the intended image appears as it should. I can't for the life of me figure out where the error is... can any one of you help?

Thanks a lot!

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So I've tried adding both gl.glDisable(GL.GL_DEPTH_TEST) and gl.glClear(GL.GL_DEPTH_BUFFER_BIT) to my code (independently and together) and now the problem's got even weirder... Sometimes when the program runs, the scene flickers and disappears, whereas other times it stays on screen without disappearing.

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some quick thoughts:

1.to center your frame on the screen just use this single line

[code]setLocationRelativeTo(null);[/code]

2. you should move your viewport and projection setup calls to the reshape method and replace 500/300 with width/height


3. don't have each point you render in a single begin end "bracket". Do a glBegin infront the loop and a glEnd after it.

4. [color="#1C2837"][color="#000000"]gl[/color][color="#666600"].[/color][color="#000000"]glClear[/color][color="#666600"]([/color][color="#000000"]GL[/color][color="#666600"].[/color][color="#000000"]GL_COLOR_BUFFER_BIT | [/color][/color][color="#1C2837"][size="2"]GL.GL_DEPTH_BUFFER_BIT[/size][/color][color="#666600"]);[/color]


Finally, your Problem is that u don't use an Animator. An Animator is an Thread in JOGL who calls your display function over and over again.

just use these two lines

[code]Animator a = new Animator(canvas);
a.start();[/code]

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