Как сделать анимацию снега, используя SFML?

#include <SFML/Graphics.hpp> 
 
 
class ParticleSystem : public sf::Drawable, public sf::Transformable
{
public:
 
    ParticleSystem(unsigned int count) :
    m_particles(count),
    m_vertices(sf::Points, count),
    m_lifetime(sf::seconds(3)),
    m_emitter(0, 0)
    {
    }
 
    void setEmitter(sf::Vector2f position)
    {
        m_emitter = position;
    }
 
    void update(sf::Time elapsed)
    {
        for (std::size_t i = 0; i < m_particles.size(); ++i)
        {
            // update the particle lifetime
            Particle& p = m_particles[i];
            p.lifetime -= elapsed;
 
            // if the particle is dead, respawn it
            if (p.lifetime <= sf::Time::Zero)
                resetParticle(i);
 
            // update the position of the corresponding vertex
            m_vertices[i].position += p.velocity * elapsed.asSeconds();
 
            // update the alpha (transparency) of the particle according to its lifetime
            float ratio = p.lifetime.asSeconds() / m_lifetime.asSeconds();
            m_vertices[i].color.a = static_cast<sf::Uint8>(ratio * 255);
        }
    }
 
private:
 
    virtual void draw(sf::RenderTarget& target, sf::RenderStates states) const
    {
        // apply the transform
        states.transform *= getTransform();
 
        // our particles don't use a texture
        states.texture = NULL;
 
        // draw the vertex array
        target.draw(m_vertices, states);
    }
 
private:
 
    struct Particle
    {
        sf::Vector2f velocity;
        sf::Time lifetime;
    };
 
    void resetParticle(std::size_t index)
    {
        // give a random velocity and lifetime to the particle
        float angle = (std::rand() % 360) * 3.14f / 180.f;
        float speed = (std::rand() % 50) + 50.f;
        m_particles[index].velocity = sf::Vector2f(std::cos(angle) * speed, std::sin(angle) * speed);
        m_particles[index].lifetime = sf::milliseconds((std::rand() % 2000) + 1000);
 
        // reset the position of the corresponding vertex
        m_vertices[index].position = m_emitter;
    }
 
    std::vector<Particle> m_particles;
    sf::VertexArray m_vertices;
    sf::Time m_lifetime;
    sf::Vector2f m_emitter;
};
int main()
{
    // create the window
    sf::RenderWindow window(sf::VideoMode(512, 256), "Particles");
 
    // create the particle system
    ParticleSystem particles(1000);
 
    // create a clock to track the elapsed time
    sf::Clock clock;
 
    // run the main loop
    while (window.isOpen())
    {
        // handle events
        sf::Event event;
        while (window.pollEvent(event))
        {
            if(event.type == sf::Event::Closed)
                window.close();
        }
 
        // make the particle system emitter follow the mouse
    
         sf::Vector2i mouse = sf::Mouse::getPosition(window);
        particles.setEmitter(window.mapPixelToCoords(mouse));
        // update it
        sf::Time elapsed = clock.restart();
        particles.update(elapsed);
        
        // draw it
        window.clear( );
        window.draw(particles);
        window.display();
    }
 
    return 0;
}