C++ code for planet simulation

The following code is part of the CauseF program, Menus and scenarios - Planets.

In particular it serves to create the trajectories of the planets in 3D space, rendered here as their paths:

planet paths

    
   grav_tmp = gravitation;

   grav_tmp *= ball_1.mass * ball_array[i].mass;//here the centre is the attractor

   if (dist != 0.0f)

     grav_tmp *= 1.0f / dist;//force strength is inversely proportional to the distance

   gravity_v = subtract_vector(ball_1.pos, ball_array[i].pos);

   gravity_v = normalise_vector(gravity_v, &l);

   gravity_v = multiply_vector(gravity_v, grav_tmp, 3);

   ball_array[i].vel = add_vector(gravity_v, ball_array[i].vel);

   tmp = ball_array[i].vel;

   apply_forcefield(tmp, gravity_v, forcefield_factor, &ball_array[i].vel, 0, 0, 0, 0.0f, 0.0f, 0.0f);

   if (continuous_ssf_flag == 0)

     speed_small_factor = 1.0f;

   ball_array[i].vel = multiply_vector(ball_array[i].vel, speed_small_factor, 3);

   ball_array[i].pos = add_vector(ball_array[i].pos, ball_array[i].vel);