variabletimestepgame.java

java 3d game jme 工程开发源代码

/*
 * Copyright (c) 2003-2009 jMonkeyEngine
 * 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 'jMonkeyEngine' 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.
 */
// $Id: VariableTimestepGame.java 4091 2009-01-21 19:01:20Z joshua.j.ellen $
package com.jme.app;

import java.util.logging.Level;
import java.util.logging.Logger;

import com.jme.input.InputSystem;
import com.jme.util.Timer;
import com.jme.system.GameSettings;

/**
 * A game that tracks time between frames.
 * <p>
 * This is identical to {@link BaseGame} except that it also maintains a timer
 * which is used to pass frame timing information to the render and update
 * methods. This is useful if a game needs to execute a different amount of
 * logic based upon the elapsed time.
 * 
 * @author Eric Woroshow
 * @version $Revision: 4091 $, $Date: 2009-01-22 03:01:20 +0800 (星期四, 22 一月 2009) $
 */
public abstract class VariableTimestepGame extends AbstractGame {
    private static final Logger logger = Logger
            .getLogger(VariableTimestepGame.class.getName());

    //Timing stuff
    private Timer timer;

    private float frametime;

    /**
     * <code>getFramesPerSecond</code> gets the current frame rate.
     * 
     * @return the current number of frames rendering per second
     */
    public float getFramesPerSecond() {
        return 1 / frametime;
    }

    /**
     * <code>updateTime</code> calculates the start and stop time of the
     * frame.
     */
    private void updateTime() {
        timer.update();
        frametime = timer.getTimePerFrame();
    }

    /**
     * Renders and updates logic as fast as possible, but keeps track of time
     * elapsed between frames.
     */
    public final void start() {
        logger.info("Application started.");
        try {
            getAttributes();

            initSystem();

            assertDisplayCreated();

            timer = Timer.getTimer();
            
            initGame();

            //main loop
            while (!finished && !display.isClosing()) {
                //determine time elapsed since last frame
                updateTime();

                //handle input events prior to updating the scene
                // - some applications may want to put this into update of the game state
                InputSystem.update();

                //update game state, pass amount of elapsed time
                update(frametime);

                //render, do not use interpolation parameter
                render(-1.0f);

                //swap buffers
                display.getRenderer().displayBackBuffer();

                Thread.yield();
            }
        } catch (Throwable t) {
            logger.logp(Level.SEVERE, this.getClass().toString(), "start()", "Exception in game loop", t);
        } finally {
            cleanup();
        }
        logger.info("Application ending.");

        if (display != null) {
            display.reset();
        }
        quit();
    }

    /**
     * Quits the program abruptly using <code>System.exit</code>.
     * 
     * @see AbstractGame#quit()
     */
    protected void quit() {
        if (display != null) {
            display.close();
        }
        System.exit(0);
    }

    /**
     * @param deltaTime
     *            the time elapsed since the last frame, in seconds
     * @see AbstractGame#update(float interpolation)
     */
    protected abstract void update(float deltaTime);

    /**
     * @param interpolation
     *            unused in this implementation
     * @see AbstractGame#render(float interpolation)
     */
    protected abstract void render(float interpolation);

    /**
     * @see AbstractGame#initSystem()
     */
    protected abstract void initSystem();

    /**
     * @see AbstractGame#initGame()
     */
    protected abstract void initGame();

    /**
     * @see AbstractGame#reinit()
     */
    protected abstract void reinit();

    /**
     * @see AbstractGame#cleanup()
     */
    protected abstract void cleanup();

  /**
   * TODO:  Implement
   * @see AbstractGame#getNewSettings
   */
  protected GameSettings getNewSettings() {
      return null;
  }
}