LWJGL Game Init and Main Loop

princec

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LWJGL Game Init and Main Loop

« Posted 2004-04-16 10:47:22 »

With the advent of LWJGL 0.9 marking a freeze in the API I thought there might be some clubies who'd like to see how simple a LWJGL game can look.

So here is a complete Game class. Fill in the blanks with your game Wink

(This code is checked into LWJGL CVS too)

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/*
 * Copyright (c) 2002 Light Weight Java Game Library Project
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 * * Redistributions of source code must retain the above copyright
 *   notice, this list of conditions and the following disclaimer.
 *
 * * Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * * Neither the name of 'Light Weight Java Game Library' nor the names of
 *   its contributors may be used to endorse or promote products derived
 *   from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package org.lwjgl.examples;

import org.lwjgl.Sys;
import org.lwjgl.input.Keyboard;
import org.lwjgl.openal.AL;
import org.lwjgl.opengl.GL11;
import org.lwjgl.opengl.Window;

/**
 * $Id: Game.java,v 1.3 2004/05/05 14:35:05 cix_foo Exp $
 *
 * This is a <em>very basic</em> skeleton to init a game and run it.
 *
 * @author $Author: cix_foo $
 * @version $Revision: 1.3 $
 */
public class Game {
      
      /** Game title */
      public static final String GAME_TITLE = "My Game";
      
      /** Desired frame time */
      private static final int FRAMERATE = 60;
      
      /** Exit the game */
      private static boolean finished;
      
      /**
       * No constructor needed - this class is static
       */
      private Game() {}
      
      /**
       * Application init
       * @param args Commandline args
       */
      public static void main(String[] args) {
            try {
                  init();
                  run();
            } catch (Exception e) {
                  e.printStackTrace(System.err);
                  Sys.alert(GAME_TITLE, "An error occured and the game will exit.");
            } finally {
                  cleanup();
            }
      }
      
      /**
       * Initialise the game
       * @throws Exception if init fails
       */
      private static void init() throws Exception {
            // Create a fullscreen window with 1:1 orthographic 2D projection, and with
            // mouse, keyboard, and gamepad inputs.
            Window.create(GAME_TITLE);
            
            // Enable vsync if we can
            Window.setVSyncEnabled(true);
            
            // Start up the sound system
            AL.create();
            
            // TODO: Load in your textures etc here
      }
      
      /**
       * Runs the game (the "main loop")
       */
      private static void run() {
            while (!finished) {
                  // Always call Window.update(), all the time
                  Window.update();
                  
                  if (Window.isCloseRequested()) {
                        // Check for O/S close requests
                        finished = true;
                  } else if (Window.isActive()) {
                        // The window is in the foreground, so we should play the game
                        logic();
                        render();
                        org.lwjgl.Display.sync(FRAMERATE);
                  } else {
                        // The window is not in the foreground, so we can allow other stuff to run and
                        // infrequently update
                        try {
                              Thread.sleep(100);
                        } catch (InterruptedException e) {
                        }
                        logic();
                        if (Window.isVisible() || Window.isDirty()) {
                              // Only bother rendering if the window is visible or dirty
                              render();
                        }
                  }
            }
      }
      
      /**
       * Do any game-specific cleanup
       */
      private static void cleanup() {
            // TODO: save anything you want to disk here

            // Stop the sound
            AL.destroy();
            
            // Close the window
            Window.destroy();
      }
      
      /**
       * Do all calculations, handle input, etc.
       */
      private static void logic() {
            // Example input handler: we'll check for the ESC key and finish the game instantly when it's pressed
            if (Keyboard.isKeyDown(Keyboard.KEY_ESCAPE)) {
                  finished = true;
            }
            // TODO: all your game logic goes here.
      }
      
      /**
       * Render the current frame
       */
      private static void render() {
            GL11.glClear(GL11.GL_COLOR_BUFFER_BIT | GL11.GL_STENCIL_BUFFER_BIT);
            // TODO: all your rendering goes here
      }

}

<edit> fixed a bug in cleanup
<edit2> New timing code!

Cas

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