👁️Observers, Global Observers, and Observer Objects

v1.0

Observers are passive watchers of lifecycle events, and can act depending on what they see. Observer Objects are Monobehaviours which can watch a Projectile.

Observer Scriptable Object

The Observer class derives from ProjectileBehavior, as do all of the other Behavior classes, giving it access to lifecycle events on Projectiles. While behaviors aim to act upon the Projectile itself, an Observer is intended to act upon something external to the Projectile.

The Demo Actor Observer in the demo scene is used to recognize when a projetile fired by the "Player" Actor collides with a "Target" Actor in order to compute and transfer damage to the target.

The Turn Off On Collision Observer is used to turn off a GameObject whenever a specific Projectile collides with something.

Observers are a great way to hook into the Projectile Factory system, and connect your game to the lifecycle events. This means you'll likely want to create your own Observers. Check out the Create Custom Behaviors page for more details on how (easy it is) to create custom behaviors and observers.

There are two ways to attach an Observer ScriptableObject to a Projectile.

Attach via the ProjectileSpawner

The Projectile Spawner has an Observers List<Observer>. Each Projectile that is created by this Spawner will be given an instance of each Observer in the list. This is how the Demo Actor Observer is added to all Projectiles the player spawns.

Global Observer

A Global Observer is an object that intends to be interested in Projectiles spawned by more than just one ProjectileSpawner. In the demo scenes, the Camera has a GlobalObserver class on it, which shakes the camera anytime a projectile collides.

Global Observers subscribe to the Factory Manager, which repeats events from the Projectiles registered to it.

Observer Example

The Projectile Spawner also has one Observer assigned to the Observers list.

This observer has no exposed parameters. As an ProjectileObserver, it automatically subscribes to all lifecycle events on each Projectile spawned -- this class inherits from ProjectileBehavior, as do all of the Behaviors.

Whenever CollisionEnter or TriggerEnter is called by a Projectile, the HitObject method on this observer is called. If the HitObject has a ProjectileDemoActor component, then the Actor who spawned the projectile will run the RegisterHit method, which computes damage and passes it to the hit Actor.

This Projectile Observer is a demo class, intended to showcase one way of connecting your project to the Projectile Factory events. Each project is unique, and you can choose for yourself the most efficient way to get the information you need to process data for your game.

Global Observer Example

The Factory Manager exists in all scenes, as it is a Static Scriptable Object. This manager maintains a List of all ProjectileSpawner and Projectile objects in the scene, along with global observers, which are ProjectileObserver objects.

In the demo scene, the Camera has a CameraShakeOnProjectileCollision component on it. This class inherits from GlobalObserver. This means it automatically subscribes to the FactoryManager lifecycle events.

The class overrides the CollisionEnter method, which is called whenever ANY projectile that is registered with the FactoryManager collides.

protected override void CollisionEnter(Projectile basicProjectile, Collision collision, GameObject objectHit = null, Vector3 contactPoint = default)
{
     var valueOnCurve = DistanceValueOnCurve(contactPoint);
     ShakeCamera(shakeDuration * valueOnCurve, shakeMagnitude * valueOnCurve, shakeFrequency * valueOnCurve);
}

Whenever this occurs, the method will shake the camera, with the shake impact determined by the distance the collision is from the camera itself.

Observer Object Example

Observer Objects are MonoBehaviours which connect to an external Projectile, and have access to all the lifecycle events on that Projectile. Each one will derive from ObserverObject.

In the example above, the ToggleObjectAtEventsObserverObject will turn the list of objects on and off at the defined events.

I prefer to include "ObserverObject" in the class name. It's easier to find, and more clear what kind of class it is.

Spawner Observer Object Example

Spawner Observer Objects are MonoBehaviours which connect to a ProjectileSpawner, and have access to all the lifecycle events on that spawner. Each one will derive from SpawnerObserverObject.

The SpawnOnSpawnPointsSpawnerObserverObject will spawn objects onto one or all of the Spawn Points at the events you select. In the example above, the objects will be spawned when the projecitles start shooting, and will be destroyed when they stop shooting. We use it in one of the Integraitons to show a "charging" particle, along with a Projectile that has a 0.5 second delay.