# Prefab main actor

In Hology Engine, a **Main Actor** allows you to define the primary identity of a prefab. By designating a specific actor within a prefab as the "Main Actor", the prefab itself effectively adopts that actor's type.

This concept creates an "is-a" relationship between the prefab and its main actor. For instance, a complex `SciFiSlidingDoor` prefab containing meshes, sounds, and particle effects can be designated to *be* a `DoorActor`.

### Why use a Main Actor?

Setting a main actor provides two major benefits for gameplay engineering and level design:

#### 1. Referencing in the Editor

When a prefab has a main actor, instances of that prefab can be assigned to component parameters that expect the main actor's type.

**Example:** Imagine you have a `PressurePlate` actor in your scene that has a property `target` of type `DoorActor`.

* **Without Main Actor**: You cannot reference the `SciFiSlidingDoor` prefab instance in the `target` parameter because the engine sees it merely as a generic prefab or group.
* **With Main Actor**: If the `SciFiSlidingDoor` prefab has its internal `DoorActor` actor set as the Main Actor, you can reference the `SciFiSlidingDoor` instance directly into the `PressurePlate`'s `target` parameter. The engine resolves this reference to the internal `DoorActor` actor automatically.

#### 2. Parameter Overrides

Parameters on the Main Actor become exposed on the prefab instance in the scene editor.

This allows level designers to tweak gameplay values (like `OpenSpeed` or `Locked`) directly on the prefab instance without needing to dig into the prefab hierarchy to find the specific logic actor.

### How to set a Main Actor

1. Open the prefab you want to edit.
2. In the **Outliner**, find the actor that represents the core logic or identity of the prefab.
3. Right-click the actor and select **Set as Main Actor**.

#### Unsetting

To remove the association, right-click the current Main Actor in the Outliner and select **Unset Main Actor**.