idle_func

void idle_func(void)
{
    custom_math::vector_3 grav_dir = sun_pos - mercury_pos;
    
    float distance = grav_dir.length();

    grav_dir.normalize();
    custom_math::vector_3 accel = grav_dir*(G*sun_mass/pow(distance, 2.0));
    
    float dt = 10000;

    mercury_vel = mercury_vel + accel*dt;
    mercury_pos = mercury_pos + mercury_vel*dt;
    
    positions.push_back(mercury_pos);
    
    glutPostRedisplay();
}