使用C++与SFML编写一个简单的撞球游戏Part8——添加AI弹板

一个人玩未免有点沉闷，现在让我们来添加一个AI弹板来充当对手吧！！！

AIPaddle.h

#pragma once
#include "visiblegameobject.h"
class AIPaddle :
    public VisibleGameObject
{
public:
    AIPaddle(void);
    ~AIPaddle(void);

    void Update(float elapsedTime);
    void Draw(sf::RenderWindow& rw);

    float GetVelocity() const;

private:
    float _velocity; 
    float _maxVelocity;
};

AIPaddle.cpp

#include "StdAfx.h"
#include "AIPaddle.h"
#include "Game.h"
#include "GameBall.h"

AIPaddle::AIPaddle() :
    _velocity(0),
    _maxVelocity(600.0f)
{
    Load("images/paddle.png");
    assert(IsLoaded());

    GetSprite().setOrigin(GetSprite().getLocalBounds().width /2, GetSprite().getLocalBounds().height / 2);
}


AIPaddle::~AIPaddle()
{
}

void AIPaddle::Draw(sf::RenderWindow & rw)
{
    VisibleGameObject::Draw(rw);
}

float AIPaddle::GetVelocity() const
{
    return _velocity;
}

void AIPaddle::Update(float elapsedTime)
{
    const GameBall* gameBall = static_cast<GameBall*>
        (Game::GetGameObjectManager().Get("Ball"));
    sf::Vector2f ballPosition = gameBall->GetPosition();

    if(GetPosition().x -20 < ballPosition.x)
        _velocity += 15.0f;
    else if(GetPosition().x +20 > ballPosition.x)
        _velocity -= 10.0f;
    else
        _velocity = 0.0f;


    if(_velocity > _maxVelocity)
        _velocity = _maxVelocity;

    if(_velocity < -_maxVelocity)
        _velocity = -_maxVelocity;


    sf::Vector2f pos = this->GetPosition();

    if(pos.x  <= GetSprite().getLocalBounds().width/2
        || pos.x >= (Game::SCREEN_WIDTH - GetSprite().getLocalBounds().width/2))
    {
        _velocity = -_velocity; 
    }

    GetSprite().move(_velocity * elapsedTime, 0);
}

由于AI弹板也会反弹弹球，所以要把GameBall.cpp做一些更改

#include "StdAfx.h"
#include "GameBall.h"
#include "Game.h"

GameBall::GameBall() :
    _velocity(230.0f),
    _elapsedTimeSinceStart(0.0f)
{
    //assert方法作用：括号里面的表达式必须返回true，若返回false则会出现系统错误
    Load("images/ball.png");
    assert(IsLoaded());

    GetSprite().setOrigin(15,15);

    //设置弹球的移动方向为1到360之间的随机值
    _angle = std::rand() % 360 + 1; 
    //_angle = (float)(sf::Randomizer::Random(0,360);
}


GameBall::~GameBall()
{
}


void GameBall::Update(float elapsedTime)
{
    _elapsedTimeSinceStart += elapsedTime;

    // 设置弹球在开始游戏3秒后才开始更新
    if(_elapsedTimeSinceStart < 3.0f)
        return;

    //弹球每帧的移动距离
    float moveAmount = _velocity * elapsedTime;

    //水平位移
    float moveByX = LinearVelocityX(_angle) * moveAmount;
    //垂直位移
    float moveByY = LinearVelocityY(_angle) * moveAmount;


    //获取玩家弹板
    PlayerPaddle* player1 = dynamic_cast<PlayerPaddle*>(Game::GetGameObjectManager().Get("Paddle1"));
    if(player1 != NULL)
    {
        //存储玩家弹板的矩形区域
        sf::Rect<float> p1BB = player1->GetBoundingRect();
        
        //检测玩家弹板的矩形区域与弹球的矩形区域是否有重叠
        //有则表示发生了碰撞，然后处理相关反弹的细节
        if(p1BB.intersects(GetBoundingRect()))
        { 
            _angle =  360.0f - (_angle - 180.0f);
            if(_angle > 360.0f)
                _angle -= 360.0f;

            moveByY = -moveByY;

            // 确保弹球不会跑到弹板的矩形区域内
            if(GetBoundingRect().width > player1->GetBoundingRect().top)
            {
                SetPosition(GetPosition().x,player1->GetBoundingRect().top - GetWidth()/2 -1 );
            }

            
            float playerVelocity1 = player1->GetVelocity();

            //当弹板向左移动时
            if(playerVelocity1 < 0)
            {
                //使弹球角度减少
                _angle -= 20.0f;
                if(_angle < 0 )
                    _angle = 360.0f - _angle;
            }
            else if(playerVelocity1 > 0)
            {
                _angle += 20.0f;
                if(_angle > 360.0f)
                    _angle = _angle - 360.0f;
            }
            //每次碰撞弹板都使弹球速度增加
            _velocity += 5.0f;
        }
        
    }



    //敌人AI的设置
    AIPaddle* player2 = dynamic_cast<AIPaddle*>(Game::GetGameObjectManager().Get("Paddle2"));
    if(player2 != NULL)
    {
        //存储AI弹板的矩形区域
        sf::Rect<float> p2BB = player2->GetBoundingRect();

        //检测AI弹板的矩形区域与弹球的矩形区域是否有重叠
        //有则表示发生了碰撞，然后处理相关反弹的细节
        if(p2BB.intersects(GetBoundingRect()))
        { 
            _angle =  360.0f - (_angle - 180.0f);
            if(_angle > 360.0f)
                _angle -= 360.0f;

            moveByY = -moveByY;

            // 确保弹球不会跑到弹板的矩形区域内
            if(GetBoundingRect().width > player2->GetBoundingRect().width)
            {
                SetPosition(GetPosition().x,player2->GetBoundingRect().width - GetWidth()/2 -1 );
            }


            float playerVelocity2 = player2->GetVelocity();

            //当弹板向左移动时
            if(playerVelocity2 < 0)
            {
                //使弹球角度减少
                _angle -= 20.0f;
                if(_angle < 0 )
                    _angle = 360.0f - _angle;
            }
            else if(playerVelocity2 > 0)
            {
                _angle += 20.0f;
                if(_angle > 360.0f)
                    _angle = _angle - 360.0f;
            }
            //每次碰撞弹板都使弹球速度增加
            _velocity += 5.0f;
        }
    }


    //当弹球碰撞到屏幕两边时的处理
    if(GetPosition().x + moveByX <= 0 + GetWidth()/2 
        || GetPosition().x + GetHeight()/2 + moveByX >= Game::SCREEN_WIDTH)
    {
        //调整方向以及更改水平位移使其反弹
        _angle = 360.0f - _angle;
        if(_angle > 260.0f && _angle < 280.0f)
            _angle += 20.0f;
        if(_angle > 80.0f && _angle < 100.0f)
            _angle += 20.0f;
        moveByX = -moveByX;
    }


    //当弹球碰撞到屏幕上方则令其反弹
    if(GetPosition().y - GetHeight()/2 <= 0)
    {
//         _angle =  180 - _angle;
//         moveByY = -moveByY;        
        GetSprite().setPosition(Game::SCREEN_WIDTH/2, Game::SCREEN_HEIGHT/2);
        _angle = std::rand() % 360 + 1;
        _velocity = 220.0f;
        _elapsedTimeSinceStart = 0.0f;
    }


    //当弹球落到比弹板低的地方则重置弹球
    if(GetPosition().y + GetHeight()/2 + moveByY >= Game::SCREEN_HEIGHT)
    {
        GetSprite().setPosition(Game::SCREEN_WIDTH/2, Game::SCREEN_HEIGHT/2);
        _angle = std::rand() % 360 + 1;
        _velocity = 220.0f;
        _elapsedTimeSinceStart = 0.0f;
    }


    //弹球的移动函数
    GetSprite().move(moveByX,moveByY);

}

float GameBall::LinearVelocityX(float angle)
{
    angle -= 90;
    if (angle < 0)
        angle = 360 + angle;
    return (float)std::cos( angle * ( 3.1415926 / 180.0f ));
}

float GameBall::LinearVelocityY(float angle)
{
    angle -= 90;
    if (angle < 0)
        angle = 360 + angle;
    return (float)std::sin( angle * ( 3.1415926 / 180.0f ));
}

最后还要回到Game.cpp中把AI弹板加进去（Game.h别忘记include AIPaddle）

//添加玩家弹板并设置其位置
  PlayerPaddle *player1 = new PlayerPaddle();
  player1->Load("images/paddle.png");
  player1->SetPosition((SCREEN_WIDTH/2),700);

  //添加敌人AI
  AIPaddle * player2 = new AIPaddle();
  player2->SetPosition((SCREEN_WIDTH/2),40);

  //添加弹球
  GameBall *ball = new GameBall();
  ball->SetPosition((SCREEN_WIDTH/2),(SCREEN_HEIGHT/2)-15);

  _gameObjectManager.Add("Paddle1",player1);
  _gameObjectManager.Add("Paddle2",player2);
  _gameObjectManager.Add("Ball",ball);

于是一个游戏的雏形就此诞生了

如果觉得过程太乱的话，下载完整代码回去慢慢查看吧~~~~~

Part1

Part2