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
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，
3、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
4、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
5、写个 IFire 接口，所有可开火的对象都要实现该接口
6、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);
}
}
}
}
}
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#p#
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;
}
}
}
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#p#
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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原文链接：http://www.cnblogs.com/webabcd/archive/2009/06/22/1508042.html
