Hi, I’ve recently discovered a bug in some simple JOGL (Java Open Graphics Library) code that I was writing and can’t figure out how to fix it. It seems that the depth buffer isn’t working at all. In my code there is a stationary triangle and a moving square, when the square passes behind the triangle it looks like it’s in front of the triangle instead of behind!
Here is the output:
init:
Deleting: /home/austin/NetBeansProjects/JOGLCoreClasses/build/built-jar.properties
deps-jar:
Updating property file: /home/austin/NetBeansProjects/JOGLCoreClasses/build/built-jar.properties
Compiling 1 source file to /home/austin/NetBeansProjects/JOGLCoreClasses/build/classes
compile:
run:
INIT GL IS: com.sun.opengl.impl.GLImpl
do_wait: drmWaitVBlank returned -1, IRQs don't seem to be working correctly.
Try adjusting the vblank_mode configuration parameter.
BUILD SUCCESSFUL (total time: 18 seconds)
Here is my code:
package Example;
import com.sun.opengl.util.Animator;
import java.awt.Frame;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import javax.media.opengl.GL;
import javax.media.opengl.GLAutoDrawable;
import javax.media.opengl.GLCanvas;
import javax.media.opengl.GLEventListener;
import javax.media.opengl.glu.GLU;
/**
* JOGLCoreClasses.java
* author: Brian Paul (converted to Java by Ron Cemer and Sven Goethel) <P>
*
* This version is equal to Brian Paul's version 1.2 1999/10/21
*/
public class JOGLExample implements GLEventListener {
float x = 0;
public static void main(String[] args) {
Frame frame = new Frame("Simple JOGL Application");
GLCanvas canvas = new GLCanvas();
canvas.addGLEventListener(new JOGLCoreClasses());
frame.add(canvas);
frame.setSize(640, 480);
final Animator animator = new Animator(canvas);
frame.addWindowListener(new WindowAdapter() {
@Override
public void windowClosing(WindowEvent e) {
// Run this on another thread than the AWT event queue to
// make sure the call to Animator.stop() completes before
// exiting
new Thread(new Runnable() {
public void run() {
animator.stop();
System.exit(0);
}
}).start();
}
});
// Center frame
frame.setLocationRelativeTo(null);
frame.setVisible(true);
animator.start();
}
public void init(GLAutoDrawable drawable) {
// Use debug pipeline
// drawable.setGL(new DebugGL(drawable.getGL()));
GL gl = drawable.getGL();
System.err.println("INIT GL IS: " + gl.getClass().getName());
// Enable VSync
gl.setSwapInterval(1);
// Setup the drawing area and shading mode
gl.glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
gl.glShadeModel(GL.GL_SMOOTH); // try setting this to GL_FLAT and see what happens.
}
public void reshape(GLAutoDrawable drawable, int x, int y, int width, int height) {
GL gl = drawable.getGL();
GLU glu = new GLU();
if (height <= 0) { // avoid a divide by zero error!
height = 1;
}
final float h = (float) width / (float) height;
gl.glViewport(0, 0, width, height);
gl.glMatrixMode(GL.GL_PROJECTION);
gl.glLoadIdentity();
glu.gluPerspective(45.0f, h, 1.0, 20.0);
gl.glMatrixMode(GL.GL_MODELVIEW);
gl.glLoadIdentity();
}
public void display(GLAutoDrawable drawable) {
x += 0.1;
GL gl = drawable.getGL();
// Clear the drawing area
gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);
// Reset the current matrix to the "identity"
gl.glLoadIdentity();
// Move the "drawing cursor" around
gl.glTranslatef(-1.5f, 0.0f, -6.0f);
// Drawing Using Triangles
gl.glBegin(GL.GL_TRIANGLES);
gl.glColor3f(1.0f, 0.0f, 0.0f); // Set the current drawing color to red
gl.glVertex3f(0.0f, 1.0f, 0.0f); // Top
gl.glColor3f(0.0f, 1.0f, 0.0f); // Set the current drawing color to green
gl.glVertex3f(-1.0f, -1.0f, 0.0f); // Bottom Left
gl.glColor3f(0.0f, 0.0f, 1.0f); // Set the current drawing color to blue
gl.glVertex3f(1.0f, -1.0f, 0.0f); // Bottom Right
// Finished Drawing The Triangle
gl.glEnd();
// Move the "drawing cursor" to another position
gl.glLoadIdentity();
gl.glTranslatef(0.0f, 0.0f, -6.0f);
gl.glRotatef(x, 0, 1, 0);
gl.glTranslatef(1.5f, 0.0f, 0.0f);
// Draw A Quad
gl.glBegin(GL.GL_QUADS);
gl.glColor3f(0.5f, 0.5f, 1.0f); // Set the current drawing color to light blue
gl.glVertex3f(-1.0f, 1.0f, 0.0f); // Top Left
gl.glVertex3f(1.0f, 1.0f, 0.0f); // Top Right
gl.glVertex3f(1.0f, -1.0f, 0.0f); // Bottom Right
gl.glVertex3f(-1.0f, -1.0f, 0.0f); // Bottom Left
// Done Drawing The Quad
gl.glEnd();
// Flush all drawing operations to the graphics card
gl.glFlush();
}
public void displayChanged(GLAutoDrawable drawable, boolean modeChanged, boolean deviceChanged) {
}
}
