ECS: Entities

Note

Return to the ECS page for an overview.

An Entity is meant to refer to one logical "Object". It is similar to a GameObject in the Unity Engine, or an Actor in Unreal Engine. Object is not an official Grindstone term, but is used here for the sake of explanation.

Entities in Grindstone are simply an ID that can be used to refer to one or more Components. Entities should always have at least a Transform and Tag component. You can use the Grindstone::ECS::Entity class to wrap an entity and more simply utilize the helper functions it has.

In reality, a logical "Object" may have many entities that relate to them. For example, a player may have a:

• PlayerController, which uses inputs to affect all other player entities.
• PlayerCharacter, which represents the physical position of the player.
• PlayerState, which may contain the state of non-physical data, such as the player inventory or gold.
• PlayerUserInterface, which allows for showing the HUD and menus for a player.
• PlayerWeaponHolder, which may be provided various Components depending on what type of weapon is held, and run arbitrary logic when a button is held.

Technically, each entity would not have any data or logic associated with it directly, but instead, they are given through components, including their name through the Tag component, position through the Transform component, appearance through MeshRendererComponent, and many more gameplay-specific components.