RX - how to use it in execution?

Question

I am trying to understand how to structure my program for using RX in performance.
My application has a vector of objects in a 3D world. each object occupied a field and had a “hit” stream, which is a mouse hover over it.
I was thinking about two options for structure:

Option 1

struct object_t
{
  string name_;
  box bounding_box_;
  observable<bool> hit_;
};

struct scene_t
{
  scene_t(observable<point> mouse) : hit_(hit(mouse)) 
  {
    add({"background", {/* ... */}, {}};
  }

  object_t& add(object_t o)
  {
    int object_index = objects_.size();
    o.hit_ = hit_
             .map([=](int index){ return index == object_index; })
             .distinct_until_changed();
    objects_.push_back(o);
    return objects_.back();
  }

  //! given a stream of mouse points,
  //! calculate on which object index(in objects_) the mouse is hover over. 
  //! 0 if its over the background. 
  observable<int> hit(observable<point> mouse);

  using objects_t = std::vector<object_t>;
  objects_t objects_; 
  observable<int> hit_
};

Option 2

struct object_t
{
  string name_;
  box bounding_box_;

  void signal_hit(boot is_hit) { hit_.get_observer().on_next(is_hit); }

  observable<bool> hit() const { return hit_.get_observable(); }

private:
  subject<bool> hit_;
};

struct scene_t
{
  scene_t(observable<point> mouse) : hit_(hit(mouse)) 
  {
    add({"background", {/* ... */}, {}};
    hit_
       .start_with(0)
       .buffer(2, 1) // take two hits together, the current and the previos
       .subscribe([this](std::vector<int> indices) {
          objects_[indices[1]].signal_hit(false); // we leave this one 
          objects_[indices[0]].signal_hit(true); // and entering this one
        });        
  }

  object_t& add(object_t o)
  {
    objects_.push_back(o);
    return objects_.back();
  }
  //! ... as above
};

Now the question is how to associate the result of the hit function with the stream object_t :: hit.
I see two ways:

• Option 1 is fully functional, but works very poorly, since for each mouse point the stream of all objects will have to calculate their value.
• 2. , . , , () () .

: rxcpp, , RX, FRP, rxjs\rx.net\frp ..
: -)

Answer 1

N , , , N . , .