Source code tutorial Java-OpenGL [Timing] Oleh Sugiarto Cokrowibowo

TutorialLWJGL0013.java

import org.lwjgl.LWJGLException;
import org.lwjgl.Sys;
import org.lwjgl.input.Keyboard;
import org.lwjgl.opengl.Display;
import org.lwjgl.opengl.DisplayMode;
import org.lwjgl.opengl.GL11;
 
public class TutorialLWJGL0013 {
 
    /** position of quad */
    float x = 400, y = 300;
    /** angle of quad rotation */
    float rotation = 0;
     
    /** time at last frame */
    long lastFrame;
     
    /** frames per second */
    int fps;
    /** last fps time */
    long lastFPS;
 
    public void start() {
        try {
            Display.setDisplayMode(new DisplayMode(800, 600));
            Display.setTitle("CG[LWJGL0013] || Timing");
            Display.create();
        } catch (LWJGLException e) {
            e.printStackTrace();
            System.exit(0);
        }
 
        initGL(); // init OpenGL
        getDelta(); // call once before loop to initialise lastFrame
        lastFPS = getTime(); // call before loop to initialise fps timer
 
        while (!Display.isCloseRequested()) {
            int delta = getDelta();
             
            update(delta);
            renderGL();
 
            Display.update();
            Display.sync(60); // cap fps to 60fps
        }
 
        Display.destroy();
    }
     
    public void update(int delta) {
        // rotate quad
        rotation += 0.15f * delta;
         
        if (Keyboard.isKeyDown(Keyboard.KEY_LEFT)) x -= 0.35f * delta;
        if (Keyboard.isKeyDown(Keyboard.KEY_RIGHT)) x += 0.35f * delta;
         
        if (Keyboard.isKeyDown(Keyboard.KEY_UP)) y -= 0.35f * delta;
        if (Keyboard.isKeyDown(Keyboard.KEY_DOWN)) y += 0.35f * delta;
         
        // keep quad on the screen
        if (x < 0) x = 0;
        if (x > 800) x = 800;
        if (y < 0) y = 0;
        if (y > 600) y = 600;
         
        updateFPS(); // update FPS Counter
    }
     
    /** 
     * Calculate how many milliseconds have passed 
     * since last frame.
     * 
     * @return milliseconds passed since last frame 
     */
    public int getDelta() {
        long time = getTime();
        int delta = (int) (time - lastFrame);
        lastFrame = time;
      
        return delta;
    }
     
    /**
     * Get the accurate system time
     * 
     * @return The system time in milliseconds
     */
    public long getTime() {
        return (Sys.getTime() * 1000) / Sys.getTimerResolution();
    }
     
    /**
     * Calculate the FPS and set it in the title bar
     */
    public void updateFPS() {
        if (getTime() - lastFPS > 1000) {
            Display.setTitle("FPS: " + fps);
            fps = 0;
            lastFPS += 1000;
        }
        fps++;
    }
     
    public void initGL() {
        GL11.glMatrixMode(GL11.GL_PROJECTION);
        GL11.glLoadIdentity();
        GL11.glOrtho(0, 800, 0, 600, 1, -1);
        GL11.glMatrixMode(GL11.GL_MODELVIEW);
    }
 
    public void renderGL() {
        // Clear The Screen And The Depth Buffer
        GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_DEPTH_BUFFER_BIT);
        
        GL11.glShadeModel(GL11.GL_SMOOTH); // Enables Smooth Shading
 
        // R,G,B,A Set The Color
        GL11.glClearColor(0.20392156862f, 0.59607843137f, 0.85882352941f, 0.0f);
 
        // draw quad
        GL11.glPushMatrix();
            GL11.glTranslatef(x, y, 0);
            GL11.glRotatef(rotation, 0f, 0f, 1f);
            GL11.glTranslatef(-x, -y, 0);
             
            GL11.glBegin(GL11.GL_QUADS);
            GL11.glColor3f(243.0f/255.0f, 156.0f/255.0f, 18.0f/255.0f);
                GL11.glVertex2f(x - 50, y - 50);
                GL11.glVertex2f(x + 50, y - 50);
                GL11.glVertex2f(x + 50, y + 50);
                GL11.glVertex2f(x - 50, y + 50);
            GL11.glEnd();
        GL11.glPopMatrix();
    }
     
    public static void main(String[] argv) {
    	TutorialLWJGL0013 tutorial = new TutorialLWJGL0013();
    	tutorial.start();
    }
}