cgun.cpp

实现一个大黄蜂游戏的源码

#include "CGun.h"


const int NumGunVerts = 8;
const SPoint gun[NumGunVerts] = {SPoint(2,2),
                                 SPoint(2,0),
                                 SPoint(-2,0),
                                 SPoint(-2,2),
                                 SPoint(-1,2),
                                 SPoint(-1,3),
                                 SPoint(1,3),
                                 SPoint(1,2)};

//--------------------------------- ctor ---------------------------------
//
//------------------------------------------------------------------------
CGun::CGun(): m_iTicksToNextBullet(CParams::iFiringRate),
              m_dScale(CParams::dGunScale),
              m_bAutoGun(true)
{ 
  //set its position
  m_vPos = SVector2D(CParams::WindowWidth/2, 20);
  
  //create the vertex buffer
  for (int i=0; i<NumGunVerts; ++i)
  {
    m_vecGunVB.push_back(gun[i]);
  }

  //create the bullets
  for (i=0; i<CParams::iMaxBullets; ++i)
  {   
    m_vecBullets.push_back(CBullet());
  }
}


//------------------------------ Render ----------------------------------
//
//------------------------------------------------------------------------
void CGun::Render(HDC &surface, HPEN &GunPen)
{
  WorldTransform();

  HPEN OldPen = (HPEN)SelectObject(surface, GunPen);
  
  MoveToEx(surface, m_vecGunVBTrans[0].x, m_vecGunVBTrans[0].y, NULL);

  for (int vtx=0; vtx<m_vecGunVBTrans.size(); ++vtx)
  {
    LineTo(surface, m_vecGunVBTrans[vtx].x, m_vecGunVBTrans[vtx].y);
  }

  LineTo(surface, m_vecGunVBTrans[0].x, m_vecGunVBTrans[0].y);

  int BulletCounter = 0;

  //render any active bullets
  for (int blt=0; blt<m_vecBullets.size(); ++blt)
  {
    if (m_vecBullets[blt].Active())
    {
      m_vecBullets[blt].Render(surface, GunPen);

      ++BulletCounter;
    }
  }

  SelectObject(surface, OldPen);
}


//---------------------WorldTransform--------------------------------
//
//	sets up the translation matrices for the ship and applies the
//	world transform to the ships vertex buffer
//-------------------------------------------------------------------
void CGun::WorldTransform()
{
	//copy the original vertices into the buffer about to be transformed
  m_vecGunVBTrans = m_vecGunVB;
  
  //create a transformation matrix
	C2DMatrix matTransform;
	
	//scale
	matTransform.Scale(m_dScale, m_dScale);

	//and translate
	matTransform.Translate(m_vPos.x, m_vPos.y);
	
  //now transform the ships vertices
  matTransform.TransformSPoints(m_vecGunVBTrans);

}


//----------------------------- Update -----------------------------------
//
//  Checks for user keypresses and updates the gun's parameters accordingly
//  When the gun has been updated any active bullets are also updated.
//------------------------------------------------------------------------
void CGun::Update()
{
  //if auto gun enabled, update accordingly
  if (m_bAutoGun)
  {
    AutoGun();
    
    return;
  }

  //move gun left
  if (KEYDOWN(VK_LEFT) && (!(m_vPos.x < m_dScale)))
  {
    m_vPos.x -= CParams::dMaxTranslationPerTick;   
  }

  //move right
  if ( KEYDOWN(VK_RIGHT) && (!(m_vPos.x > CParams::WindowWidth-m_dScale)) )
  {
    m_vPos.x += CParams::dMaxTranslationPerTick;   
  }
 
  //fire
  if (KEYDOWN(VK_SPACE) && (m_iTicksToNextBullet < 0))
  {
    //create a new bullet
    for (int blt=0; blt<m_vecBullets.size(); ++blt)
    {
      //choose the first non active bullet to switch on
      if (!m_vecBullets[blt].Active())
      {
         m_vecBullets[blt].SwitchOn(m_vPos.x);

         m_iTicksToNextBullet = CParams::iFiringRate;

         break;
      }
    }
  }

  
  //now update any active bullets.
  for (int blt=0; blt<m_vecBullets.size(); ++blt)
  {
    m_vecBullets[blt].Update();
  }

  m_iTicksToNextBullet -= 1;

}


//-------------------------------- AutoGun -------------------------------
//
//  automatically updates the gun. Moves its position and fires at random
//  
//------------------------------------------------------------------------
void CGun::AutoGun()
{
  //how long it will perform each action for
  static int duration = 0;

  //the action it will perform
  static int action   = 0;

  if (duration <= 0)
  {
    //choose another direction and duration
    duration = RandInt(30, 300);
    action   = RandInt(0,2);
  }

  --duration;
  
  switch(action)
  {

  case 0:  //move left
    {
      if (m_vPos.x > m_dScale)
      {
        m_vPos.x -= CParams::dMaxTranslationPerTick;
      }

      else
      {
        action = 1;
      }
    }

  break;

  case 1:  //move right
    {
      if (m_vPos.x < CParams::WindowWidth-m_dScale)
      {
        m_vPos.x += CParams::dMaxTranslationPerTick;
      }

      else
      {
        action = 0;
      }
    }

  break;
  
  }//end switch
  

  //create a new bullet
  for (int blt=0; blt<m_vecBullets.size(); ++blt)
  {
    if (!m_vecBullets[blt].Active())
    {
       m_vecBullets[blt].SwitchOn(m_vPos.x);           

       duration = -1;

       break;
    }
  }     
  
  //update any bullets which are active
  for (blt=0; blt<m_vecBullets.size(); ++blt)
  {
    m_vecBullets[blt].Update();
  }
    
}