Hi,
I’ve got a little problem with JOGL. I wanted to learn it so I have written a demo application which animates a colored triangle.
The main thread calls via run() update() method and GLCanvas.display() in loop. update() only changes X coord of one of the triangle’s vertices; the method responsible for drawing is display(GLAutoDrawable gLAutoDrawable) from GLEventListener.
It runs OK, but when I add a delay to the animation loop, it starts to flicker. And I don’t know why. I tried to add synchronized blocks into update() and display(), but it doesn’t help.
Here is the code, it’s simple:
package cz.wanto.jogltest;
import java.awt.*;
import javax.swing.*;
import javax.media.opengl.*;
/**
*
* @author wanto
*/
public class JoglTest implements GLEventListener {
private JFrame frame;
private GLCanvas canvas;
/** Creates a new instance of JoglTest */
public JoglTest() {
frame = new JFrame("Jogl test");
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.getContentPane().setLayout(new BorderLayout());
canvas = new GLCanvas();
canvas.setPreferredSize(new Dimension(640, 480));
canvas.addGLEventListener(this);
frame.getContentPane().add(canvas);
frame.pack();
frame.setVisible(true);
}
public void run() {
long currentTime = System.currentTimeMillis();
while (true) {
long elapsedTime = System.currentTimeMillis() - currentTime;
currentTime += elapsedTime;
update(elapsedTime);
canvas.display();
// I think this delay causes flickering
try {
Thread.sleep(20);
}
catch (InterruptedException e) {}
}
}
float x1 = 320;
boolean xGrowing = true;
public void update(long elapsedTime) {
// System.out.println("Update: " + Thread.currentThread().getName());
if (xGrowing) {
x1 += 0.5 * elapsedTime;
if (x1 > 640) xGrowing = false;
}
else {
x1 -= 0.5 * elapsedTime;
if (x1 < 0) xGrowing = true;
}
}
public void draw(GL gl) {
// System.out.println("Draw: " + Thread.currentThread().getName());
gl.glClear(GL.GL_COLOR_BUFFER_BIT);
gl.glBegin(GL.GL_TRIANGLES); {
gl.glColor3f(1, 0, 0);
gl.glVertex2f(x1, 0);
gl.glColor3f(0, 1, 0);
gl.glVertex2f(0, 479);
gl.glColor3f(0, 0, 1);
gl.glVertex2f(639, 479);
} gl.glEnd();
}
/**
* @param args the command line arguments
*/
public static void main(String[] args) {
JoglTest test = new JoglTest();
test.run();
}
public void init(GLAutoDrawable gLAutoDrawable) {
GL gl = canvas.getGL();
gl.glMatrixMode(GL.GL_PROJECTION);
gl.glLoadIdentity();
gl.glOrtho(0, 640, 0, 480, -1, -1);
gl.glScalef(1 / (float)(640 / 2), -1 / (float)(480 / 2), 1);
gl.glTranslatef(-(640 / 2), -(480 / 2), 0);
}
public void display(GLAutoDrawable gLAutoDrawable) {
draw(canvas.getGL());
}
public void reshape(GLAutoDrawable gLAutoDrawable, int i, int i0, int i1, int i2) {
}
public void displayChanged(GLAutoDrawable gLAutoDrawable, boolean b, boolean b0) {
}
}
Do you know how to solve this problem? Thanks for all answers,
Wan-To
