Android Open Source - flingbox Scene Physics

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Back to project page flingbox.

License

The source code is released under:

GNU General Public License

Java Source Code

/*
 *  Flingbox - An OpenSource physics sandbox for Google's Android
 *  Copyright (C) 2009  Jon Ander Pealba & Endika Gutirrez
 *//from  w  w  w  .ja  v a2  s  . com
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package edu.eside.flingbox.physics;

import java.util.ArrayList;
import java.util.concurrent.Semaphore;

import edu.eside.flingbox.math.Vector2D;
import edu.eside.flingbox.physics.collisions.Arbiter;
import edu.eside.flingbox.physics.gravity.GravitySource;
import edu.eside.flingbox.utils.PositionComparator;

/**
 * Stores all physic object in scene and make those 
 * interact.
 * ScenePhysics manage thread for update objects 
 */
public class ScenePhysics implements Runnable {
  private final GravitySource mGravity;
  
  /** List of physical bodys on scene */
  private final ArrayList<PhysicBody> mOnSceneBodies = new ArrayList<PhysicBody>();
  /** Collision manager for current scene */
  private final Arbiter mArbiter = new Arbiter();
  
  /** Semaphore for lock writing on mOnSceneBodys */
  private Semaphore mLockOnSceneBodys = new Semaphore(1);

  /** Thread for simulation */
  private Thread mSimulationThread;
  /** Flag for kill simulation */
  private boolean mDoKill = false;
  /** Flag indicating if thread is running */
  private Semaphore mSimulationMutex = new Semaphore(1, true);
  
  /**
   * Initializes an empty scene
   */
  public ScenePhysics(final GravitySource gravity) {
    mGravity = gravity;
    PositionComparator.setGroundSense(gravity);
  }
  
  /**
   * Adds physical object
   * @param object object to be added
   */
  public void add(final PhysicBody body) {
    try {
      mLockOnSceneBodys.acquire();
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
    mOnSceneBodies.add(body);
    mArbiter.add(body.getCollider());
    mLockOnSceneBodys.release();
  }
  
  public boolean remove(final PhysicBody body) {
    try {
      mLockOnSceneBodys.acquire();
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
    boolean removed = mOnSceneBodies.remove(body);
    mLockOnSceneBodys.release();
    removed &= mArbiter.remove(body.getCollider());
    return removed;
  }
  
  /**
   * Starts simulation
   */
  public void startSimulation() {
    if (mSimulationThread != null && mSimulationThread.isAlive())
      return;
      
    mDoKill = false;
    mSimulationThread = new Thread(this);
    mSimulationThread.start();
  }
  
  /**
   * Sends message to kill and waits
   */
  public void stopSimulation() {
    mDoKill = true;
    try {
      mSimulationMutex.acquire();
    } catch (InterruptedException e) {
      e.printStackTrace();
    }
    mSimulationThread = null;
    mSimulationMutex.release();
    System.gc(); // Good moment to call to GC
  }
  
  /**
   * @return true if simulating
   */
  public boolean isSimulating() {
    return mSimulationThread != null ? mSimulationThread.isAlive() : false;
  }
  
  /**
   * Thread for simulation
   */
  @Override
  public void run() {
    final ArrayList<PhysicBody> bodies = mOnSceneBodies;
    long lastTime = System.currentTimeMillis();
    long time;
    final Vector2D force = new Vector2D();
    
    for (; !mDoKill; ) {
      try {
        mSimulationMutex.acquire();
      } catch (InterruptedException e2) {
        e2.printStackTrace();
      }
      
      /* Compute time */
      time = System.currentTimeMillis() - lastTime;
      lastTime = System.currentTimeMillis();

      /* We need a semaphore here */
      try {
        mLockOnSceneBodys.acquire();
      } catch (InterruptedException e1) {
        e1.printStackTrace();
      }
      /* Apply gravity impulse */
      for (PhysicBody body : bodies) {
        force.set(mGravity);
        body.applyImpulse(force.mul(body.getBodyMass() * (float) time / 1000f));
      }
      mLockOnSceneBodys.release();
      
      /* Then apply collisions forces */
      mArbiter.checkCollisions();
      
      try {
        mLockOnSceneBodys.acquire();
      } catch (InterruptedException e1) {
        e1.printStackTrace();
      }
      /* Last update body */
      for (PhysicBody body : bodies)
        body.onUpdateBody((float) time / 1000f);
      
      mLockOnSceneBodys.release();
      
      mSimulationMutex.release();
      /* Keep max frame-rate */
      try {
        if (time < 40) 
          Thread.sleep(40 - time);    
      } catch (InterruptedException e) {
        e.printStackTrace();
      } 
    }
    mDoKill = false;
  }

  
  
}

Java Source Code List

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