Система частиц в 2D

#include "QapLite.h"
 
class TParticle{
public:
  vec2d pos;
  vec2d v;
  real t;
public:
  TParticle()
  {
    pos=vec2d(0,0);
    v=vec2d(0,0);
    t=0.0;
  }
};
 
class TExplosion{
public:
  string name;
  bool auto_move;
  bool auto_draw;
  bool blend_add;
  vec2d pos;
  int tick;
  int max_tick;
  real particle_beg_size;
  real particle_end_size;
  QapColor particle_beg_color;
  QapColor particle_end_color;
  int particle_life_time;
  int particle_per_tick;
  real particle_min_speed;
  real particle_max_speed;
  real particle_pos_dist;
  real particle_pos_dist_var;
  vec2d particle_grav;
  bool undeadable;
  vector<TParticle> arr;
public:
  TExplosion()
  {
    name=string();
    auto_move=true;
    auto_draw=true;
    blend_add=true;
    pos=vec2d(0,0);
    tick=0;
    max_tick=64;
    particle_beg_size=8;
    particle_end_size=1;
    particle_beg_color=0xff00ff00;
    particle_end_color=0xff000000;
    particle_life_time=32;
    particle_per_tick=4;
    particle_min_speed=100.0/64.0;
    particle_max_speed=400.0/64.0;
    particle_pos_dist=4;
    particle_pos_dist_var=8;
    particle_grav=vec2d(0,0);
    undeadable=false;
    arr=vector<TParticle>();
  }
};
 
 
class TGame:public TD3DGameBoxBuilder{
public:
  vector<TExplosion> explosions;
public:
  TGame()
  {
    vec_add_back(explosions).undeadable=true;
    {
      auto&back=vec_add_back(explosions);
      back.undeadable=true;
      back.pos=vec2d(-200,0);
      back.particle_beg_color=0xff00aa00;
    }
    {
      auto&back=vec_add_back(explosions);
      back.undeadable=true;
      back.pos=vec2d(+200,0);
      back.particle_beg_color=0xff00aa00;
      back.particle_min_speed=40.0/64.0;
      back.particle_max_speed=90.0/64.0;
      back.particle_per_tick=2;
      back.particle_grav=vec2d(0,-0.2);
    }
  }
public:
  void render(TExplosion&ref)
  {
    if(!ref.auto_draw)return;
    QapDev::BatchScope Scope(qDev);
    auto&arr=ref.arr;
    for(int i=0;i<arr.size();i++)
    {
      auto&ex=arr[arr.size()-i-1];
      real t=1.0-ex.t/real(ref.particle_life_time);
      qDev.SetColor(QapColor::Mix(ref.particle_beg_color,ref.particle_end_color,t));
      qDev.DrawQuad(ex.pos,vec2d(1,1)*Lerp(ref.particle_beg_size,ref.particle_end_size,t));
    }
    qDev.SetBlendMode(QapDev::BlendType::BT_SUB);
  }
  void render(vector<TExplosion>&arr)
  {
    for(int i=0;i<arr.size();i++)
    {
      auto&ex=arr[i];
      render(ex);
    }
  }
  void update(vector<TExplosion>&arr)
  {
    clean_if(arr,[](TExplosion&ex){return !ex.undeadable&&(ex.tick>=ex.max_tick)&&ex.arr.empty();});
    for(int i=0;i<arr.size();i++)
    {
      auto&ex=arr[i];
      update(ex);
    }
  }
  void update(TExplosion&ref)
  {
    if(!ref.auto_move)return;
    ref.tick++;
    auto&arr=ref.arr;
    for(int i=0;i<arr.size();i++)
    {
      auto&ex=arr[i];
      ex.pos+=ex.v;
      ex.v+=ref.particle_grav;
      ex.t--;
    }
    clean_if(ref.arr,[](TParticle&ex){return ex.t<=0;});
    if(!ref.undeadable)if(ref.tick>=ref.max_tick)return;
    auto rnd=[]()->real{int n=1024*16;return real(rand()%n)/real(n);};
    auto rnd_ang=[&rnd]()->real{return rnd()*Pi2;};
    for(int i=0;i<ref.particle_per_tick;i++)
    {
      auto&back=vec_add_back(ref.arr);
      auto dist=ref.particle_pos_dist;
      auto dist_var=ref.particle_pos_dist_var;
      auto d=dist+dist_var*(-0.5+rnd());
      back.pos=ref.pos+Vec2dEx(rnd_ang(),d);
      auto ang=rnd_ang();
      auto mag=Lerp(ref.particle_min_speed,ref.particle_max_speed,rnd());
      back.v=Vec2dEx(ang,mag);
      back.t=ref.particle_life_time;
    }
  }
public:
  void DoMove()
  {
    if(win.Keyboard.Down[VK_ESCAPE])win.Close();
    update(explosions);
  }
  void DoDraw()
  {
    qDev.BindTex(0,nullptr);
    QapDev::BatchScope Scope(qDev);
    render(explosions);
  }
};
 
int WINAPI WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine,int nCmdShow)
{
  GlobalEnv global_env(hInstance,hPrevInstance,lpCmdLine,nCmdShow);
  TGame builder;
  builder.DoNice();
}