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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
Get Microsoft Silverlight


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 getset; }
        
private List<Key> _downKeys getset; }
        
private List<Key> _leftKeys getset; }
        
private List<Key> _rightKeys getset; }
        
private List<Key> _fireKeys getset; }

        
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 getset; }

        
public double MinFireInterval getset; }

        
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 getset; }

        
public double MinFireInterval getset; }

        
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(50200/ 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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