游戏人生Silverlight(5) - 星际竞技场[Silverlight 2.0(c#, Farseer Physics Engine)]

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游戏人生Silverlight(5) - 星际竞技场[Silverlight 2.0(c#, Farseer Physics Engine)]

作者：webabcd
物理引擎：Farseer Physics Engine


介绍
使用 Silverlight 2.0(c#, Farseer Physics Engine) 开发一个射击游戏：星际竞技场


玩法
W 或者 ↑ = 前进；S 或者 ↓ = 后退：A 或者 ← = 左转；D 或者 → = 右转；J 或者 Ctrl = 开火


在线DEMO



思路
1、使用一个开源的 Silverlight 物理引擎：Farseer Physics Engine
2、将 Farseer Physics Engine 中的物理运算器 PhysicsSimulator 放到一个全局变量中，对 Body 和 Geom 做即时运算，
2、写个 IPhysicsControl 接口，用于描述物理对象的各个属性，需要运动和碰撞的对象，要实现该接口抽象出来的各个属性
3、写个抽象类（Sprite），在其内封装好物理引擎。各种类型的物理对象的模拟器，都需要重写该抽象类的两个方法GetForce()和GetTorque()即可，其分别要返回对象在当前时刻所受到的牵引力和力矩
4、写个 IFire 接口，所有可开火的对象都要实现该接口
5、写个控件 PhysicsBox，用于包装 IPhysicsControl，从而将模拟器计算出的运动和碰撞结果呈现到界面上


关键代码 
Sprite.cs（Sprite 模拟器的基类）

 

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using FarseerGames.FarseerPhysics;
using FarseerGames.FarseerPhysics.Mathematics;
using FarseerGames.FarseerPhysics.Dynamics;
using FarseerGames.FarseerPhysics.Collisions;

namespace YYArena.Core
{
         /// <summary>
         /// Sprite 基类
         /// </summary>
         public abstract class Sprite
        {
                 private PhysicsSimulator _physicsSimulator;

                 protected PhysicsBox playerBox;
                 protected Geom playerGeometry;

                 /// <summary>
                 /// 构造函数
                 /// </summary>
                 /// <param name="physicsSimulator">PhysicsSimulator</param>
                 /// <param name="physicsControl">IPhysicsControl</param>
                 /// <param name="position">初始位置</param>
                 /// <param name="angle">初始转角</param>
                 /// <param name="originalVelocity">初始速度</param>
                 public Sprite(PhysicsSimulator physicsSimulator,
                        IPhysicsControl physicsControl, Vector2 position, float angle, float originalVelocity)
                {
                        _physicsSimulator = physicsSimulator;

                        playerBox = new PhysicsBox(physicsControl);
                        playerBox.Body.Position = position;
                        playerBox.Body.Rotation = ( float)Helper.Angle2Radian(angle);
                        playerBox.Body.LinearVelocity = Helper.Convert2Vector(originalVelocity, ( float)Helper.Angle2Radian(angle));

                         // Body 和 Geom 的 Tag 保存为 Sprite，方便引用
                        playerBox.Body.Tag = this;
                        playerBox.Geom.Tag = this;

                        playerBox.Update();
                }

                 /// <summary>
                 /// 即时计算力和力矩
                 /// </summary>
                 void CompositionTarget_Rendering( object sender, EventArgs e)
                {
                         if (Enabled)
                        {
                                var force = GetForce();
                                var torque = GetTorque();

                                playerBox.Body.ApplyForce(force);
                                playerBox.Body.ApplyTorque(torque);

                                playerBox.Update();
                        }
                }

                 /// <summary>
                 /// 返回 Sprite 当前受的力
                 /// </summary>
                 protected abstract Vector2 GetForce();
                 /// <summary>
                 /// 返回 Sprite 当前受的力矩
                 /// </summary>
                 protected abstract float GetTorque();

                 public PhysicsBox PhysicsBox
                {
                        get { return playerBox; }
                }

                 private bool _enabled = false;
                 /// <summary>
                 /// 是否启用此 Sprite
                 /// </summary>
                 public bool Enabled
                {
                        get { return _enabled; }
                        set
                        {    
                                _enabled = value;

                                 if (value)
                                {
                                        CompositionTarget.Rendering += new EventHandler(CompositionTarget_Rendering);

                                        _physicsSimulator.Add(playerBox.Body);
                                        _physicsSimulator.Add(playerBox.Geom);
                                }
                                 else
                                {
                                        CompositionTarget.Rendering -= new EventHandler(CompositionTarget_Rendering);

                                        GC.SuppressFinalize( this);
                                        _physicsSimulator.Remove(playerBox.Body);
                                        _physicsSimulator.Remove(playerBox.Geom);
                                }
                        }
                }
        }
}

PlayerSprite.cs（玩家 Sprite 模拟器）

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.Collections.Generic;
using FarseerGames.FarseerPhysics.Mathematics;
using FarseerGames.FarseerPhysics;
using FarseerGames.FarseerPhysics.Collisions;

namespace YYArena.Core
{
         /// <summary>
         /// 玩家 Sprite
         /// </summary>
         public class PlayerSprite : Sprite, IFire
        {
                 private List<Key> _upKeys { get; set; }
                 private List<Key> _downKeys { get; set; }
                 private List<Key> _leftKeys { get; set; }
                 private List<Key> _rightKeys { get; set; }
                 private List<Key> _fireKeys { get; set; }

                 private KeyboardHandler _keyHandler;
                 private IPhysicsControl _physicsControl;

                 /// <summary>
                 /// 构造函数
                 /// </summary>
                 /// <param name="physicsSimulator">PhysicsSimulator</param>
                 /// <param name="physicsControl">IPhysicsControl</param>
                 /// <param name="position">初始位置</param>
                 /// <param name="angle">初始转角</param>
                 /// <param name="originalVelocity">初始速度</param>
                 /// <param name="keyboardHandler">KeyboardHandler</param>
                 /// <param name="up">操作玩家向前移动的按键集合</param>
                 /// <param name="down">操作玩家向后移动的按键集合</param>
                 /// <param name="left">操作玩家向左转动的按键集合</param>
                 /// <param name="right">操作玩家向右转动的按键集合</param>
                 /// <param name="fire">操作玩家开火的按键集合</param>
                 public PlayerSprite(PhysicsSimulator physicsSimulator,
                        IPhysicsControl physicsControl, Vector2 position, float angle, float originalVelocity,
                        KeyboardHandler keyboardHandler,
                        List<Key> up, List<Key> down, List<Key> left, List<Key> right, List<Key> fire)
                        : base(physicsSimulator, physicsControl, position, angle, originalVelocity)
                {
                        PrevFireDateTime = DateTime.MinValue;
                        MinFireInterval = 500d;

                        _upKeys = up;
                        _downKeys = down;
                        _leftKeys = left;
                        _rightKeys = right;
                        _fireKeys = fire;

                        _keyHandler = keyboardHandler;
                        _physicsControl = physicsControl;

                        CompositionTarget.Rendering += new EventHandler(CompositionTarget_Rendering);
                }

                 void CompositionTarget_Rendering( object sender, EventArgs e)
                {
                         if (Enabled)
                        {
                                 // 如果按了开火键，是否可开火
                                 if (_keyHandler.AnyKeyPressed(_fireKeys) && (DateTime.Now - PrevFireDateTime).TotalMilliseconds > MinFireInterval)
                                {
                                        PrevFireDateTime = DateTime.Now;
                                         if (Fire != null)
                                                Fire( this, EventArgs.Empty);
                                }
                        }
                }

                 public DateTime PrevFireDateTime { get; set; }

                 public double MinFireInterval { get; set; }

                 public event EventHandler<EventArgs> Fire;

                 protected override Vector2 GetForce()
                {
                        Vector2 force = Vector2.Zero;

                         if (_keyHandler.AnyKeyPressed(_upKeys))
                                force += Helper.Convert2Vector(_physicsControl.ForceAmount, playerBox.Body.Rotation);
                         if (_keyHandler.AnyKeyPressed(_downKeys))
                                force += Helper.Convert2Vector(_physicsControl.ForceAmount, playerBox.Body.Rotation - Helper.Angle2Radian(180));

                         // 最大线性速度限制
                         if (playerBox.Body.LinearVelocity.Length() > _physicsControl.MaxLinearVelocity)
                                force = Vector2.Zero;

                         return force;
                }

                 protected override float GetTorque()
                {
                         float torque = 0;

                         if (_keyHandler.AnyKeyPressed(_leftKeys))
                                torque -= _physicsControl.TorqueAmount;
                         if (_keyHandler.AnyKeyPressed(_rightKeys))
                                torque += _physicsControl.TorqueAmount;

                         // 用于修正 RotationalDragCoefficient （在没有任何 Torque 的情况下，如果转速小于 1.3 则设其为 0）
                         // 如果不做此修正的话，转速小于 1.3 后还会转好长时间
                         if (!_keyHandler.AnyKeyPressed(_leftKeys) && !_keyHandler.AnyKeyPressed(_rightKeys) && Math.Abs(playerBox.Body.AngularVelocity) < 1.3)
                                playerBox.Body.AngularVelocity = 0;

                         // 最大转速限制
                         if (Math.Abs(playerBox.Body.AngularVelocity) > _physicsControl.MaxAngularVelocity)
                                torque = 0;

                         return torque;
                }
        }
}

AISprite.cs（敌军 Sprite 模拟器）

using System;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Ink;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;

using System.Collections.Generic;
using FarseerGames.FarseerPhysics.Mathematics;

using FarseerGames.FarseerPhysics;
using FarseerGames.FarseerPhysics.Collisions;
using FarseerGames.FarseerPhysics.Dynamics;

namespace YYArena.Core
{
         /// <summary>
         /// 敌军 Sprite
         /// </summary>
         public class AISprite : Sprite, IFire
        {
                 private Sprite _attackTarget;
                 private int _aiLevel;
                 private IPhysicsControl _physicsControl;

                 /// <summary>
                 /// 构造函数
                 /// </summary>
                 /// <param name="physicsSimulator">PhysicsSimulator</param>
                 /// <param name="physicsControl">IPhysicsControl</param>
                 /// <param name="position">初始位置</param>
                 /// <param name="angle">初始转角</param>
                 /// <param name="originalVelocity">初始速度</param>
                 /// <param name="attackTarget">攻击目标</param>
                 /// <param name="aiLevel">ai等级</param>
                 public AISprite(PhysicsSimulator physicsSimulator,
                        IPhysicsControl physicsControl, Vector2 position, float angle, float originalVelocity, Sprite attackTarget, int aiLevel)
                        : base(physicsSimulator, physicsControl, position, angle, originalVelocity)
                {
                         // 上次开火时间
                        PrevFireDateTime = DateTime.Now.AddSeconds(3);
                         // 最小开火间隔
                        MinFireInterval = 3000d;

                        _attackTarget = attackTarget;
                        _aiLevel = aiLevel;
                        _physicsControl = physicsControl;

                        InitAI();

                        CompositionTarget.Rendering += new EventHandler(CompositionTarget_Rendering);
                }

                 private void InitAI()
                {
                         // 根据 ai 等级设置最小开火间隔
                         double fireCoefficient = 1 + 30 / _aiLevel;
                        MinFireInterval = Helper.GenerateRandom(( int)MinFireInterval, ( int)(fireCoefficient * MinFireInterval));
                }

                 void CompositionTarget_Rendering( object sender, EventArgs e)
                {
                         if (Enabled && AttackTarget.Enabled)
                        {
                                 // 是否开火
                                 if ((DateTime.Now - PrevFireDateTime).TotalMilliseconds > MinFireInterval)
                                {
                                        PrevFireDateTime = DateTime.Now;

                                         if (Fire != null)
                                                Fire( this, EventArgs.Empty);
                                }
                        }
                }

                 public DateTime PrevFireDateTime { get; set; }

                 public double MinFireInterval { get; set; }

                 public event EventHandler<EventArgs> Fire;


                 public Sprite AttackTarget
                {
                        get { return _attackTarget; }
                        set { _attackTarget = value; }
                }

                 protected override Vector2 GetForce()
                {
                        Vector2 force = Vector2.Zero;

                         if (!_attackTarget.Enabled)
                                 return force;

                        force += Helper.Convert2Vector(_physicsControl.ForceAmount, playerBox.Body.Rotation);

                         // 根据 ai 等级做最大线性速度限制
                         if (playerBox.Body.LinearVelocity.Length() > _physicsControl.MaxLinearVelocity * Helper.GenerateRandom(50, 200) / 1000)
                                force = Vector2.Zero;

                         return force;
                }

                 protected override float GetTorque()
                {
                         float torque = 0f;

                         if (!_attackTarget.Enabled)
                                 return torque;

                         // 按某个方向旋转，原则是以最小的旋转角度对准目标
                        Vector2 relativePosition = _attackTarget.PhysicsBox.Body.Position - playerBox.Body.Position;
                         double targetRotation = Helper.Convert2Rotation(relativePosition);
                         double currentRotation = playerBox.Body.Rotation;
                         double relativeAngle = Helper.Radian2Angle(targetRotation - currentRotation);
                         if (relativeAngle < 0)
                                relativeAngle += 360;

                         if (relativeAngle > 1)
                        {
                                 if (relativeAngle < 180 && relativeAngle > 0)
                                        torque += _physicsControl.TorqueAmount;
                                 else if (relativeAngle > 180 && relativeAngle < 360)
                                        torque -= _physicsControl.TorqueAmount;
                        }
                         else
                        {
                                playerBox.Body.AngularVelocity = 0;
                        }


                         // 最大转速限制
                         if (Math.Abs(playerBox.Body.AngularVelocity) > _physicsControl.MaxAngularVelocity)
                                torque = 0;
                        
                         return torque;
                }
        }
}

 

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