void fill_map(int height, int width, int start, int stop, vector<pixel>& bitmap) {
        pixel ray_coord = { 0, 0, 0 };
        float pi = atan(-1.0);
        float z = -1;
        #pragma omp parallel for
        for (int i = start; i < stop; i++) {
            for (int j = 0; j < width; j++) {

                float x = (2 * (i + 0.5) / (float)width - 1) * tan(pi / 3) * width / (float)height;
                float y = -(2 * (j + 0.5) / (float)height - 1) * tan(pi / 3);
                pixel vec = { x, y, z };
                pixel direction = normalize(vec);
                pixel pix = unitize(cast_ray(ray_coord, direction));
                bitmap[j + i * width] = pix;
            }
        }
    }



    void render(string filename, int height = 768, int width = 1024) {
        vector<pixel> bitmap(width*height);

        thread t_1(std::bind(&Scene::fill_map, this, height, width, 0, int(height/8), ref(bitmap)));
        thread t_2(std::bind(&Scene::fill_map, this, height, width, int(height/8), int(height/8*2), ref(bitmap)));
        thread t_3(std::bind(&Scene::fill_map, this, height, width, int(height/8*2), int(height / 8 * 3), ref(bitmap)));
        thread t_4(std::bind(&Scene::fill_map, this, height, width, int(height/8*3), int(height / 8 * 4), ref(bitmap)));
        thread t_5(std::bind(&Scene::fill_map, this, height, width, int(height / 8 * 4), int(height / 8 * 5), ref(bitmap)));
        thread t_6(std::bind(&Scene::fill_map, this, height, width, int(height / 8 * 5), int(height / 8 * 6), ref(bitmap)));
        thread t_7(std::bind(&Scene::fill_map, this, height, width, int(height / 8 * 6), int(height / 8 * 7), ref(bitmap)));
        thread t_8(std::bind(&Scene::fill_map, this, height, width, int(height / 8 * 7), height, ref(bitmap)));

        //fill_map(height, width, 0, height, bitmap);
        t_1.join();
        t_2.join();
        t_3.join();
        t_4.join();
        t_5.join();
        t_6.join();
        t_7.join();
        t_8.join();

        SaveBMP(filename.c_str(), bitmap, width, height);

    }