Implementing new enemies or actors

Writing new BehaviorController-based actors/game objects

To implement a behavior controller, you need to declare a struct which has at least an update function:

namespace behaviors {

struct MyNewEnemy {
  void update(
    GlobalDependencies& dependencies,
    GlobalState& state,
    bool isOnScreen,
    entityx::Entity entity);
};

}

Optionally, it may also have an onCollision handler (called when it collides with the world) and/or an onKilled handler (called when killed by the player):

namespace behaviors {

struct MyNewEnemy {
  void update(
    GlobalDependencies& dependencies,
    GlobalState& state,
    bool isOnScreen,
    entityx::Entity entity);

  // Optional
  void onCollision(
    GlobalDependencies& d,
    GlobalState&,
    const engine::events::CollidedWithWorld&,
    entityx::Entity entity);

  // Optional
  void onKilled(
    GlobalDependencies& dependencies,
    GlobalState& state,
    const base::Point<float>& inflictorVelocity,
    entityx::Entity entity);
};

}

Note: It's not necessary to inherit from anything. As long as your struct/class provides the right function signatures, they will get used.

Once you have that defined, add an entry to entity_configuration.ipp to create an entity for the actor ID you're working on implementing, and then assign your behavior controller into a BehaviorController component:

  entity.assign<BehaviorController>(behaviors::MyNewEnemy{});

For an example, look at enemies\boss_episode_1.hpp.

Using state machines

Movement, collision detection etc.