Sample script using the subframe callback API.

subframe_callback.as

class script : callback_base {
  scene@ g;
  array<dustman@> players;

  script() {
    @g = get_scene();
  }

  void step(int num_entities) {
    int nc = num_cameras();

    puts("STEP");
    players.resize(nc);
    for (int i = 0; i < nc; i++) {
      dustman@ dm = @controller_entity(i).as_dustman();
      if (@dm != null && !dm.is_same(@players[i])) {
        puts("REGISTER CALLBACK");
        dm.on_subframe_end_callback(this, "subframe_cb", i);
      }
      @players[i] = @dm;
    }
  }

  void subframe_cb(dustman@ dm, int player_index) {
    puts("SUBSTEP " + player_index);
  }
}