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;
        }
    }
}

OK
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