Glossary

This page is a collection of keyword used in Godex.

• Entity
• Component

Entity

An Entity is just a container of components, differently from an Object it doesn't have any behaviour or meaning; it can be anything and it's behaviour is driven by the assigned components.

Example

You could represent the mushrooms power-ups in Mario with the following set of components:

• PhysicsBody: Used to specify this Entity has a RigidBody.
• Position: Used to specify that this Entity has a position.
• GrowPowerup: Used to specify the type of the power-up.

Or the character (Mario) could be done with the following set of components:

• PhysicsBody: Used to specify this Entity has a RigidBody.
• Position: Used to specify that this Entity has a position.
• Character: Used to specify this entity is the character.

Component

The Component is a piece of data that can be attached to an Entity. It can describe a characteristic, a state, an event of an Entity. Usually, taken alone, the components doesn't do much: but the combination of them allow building complex mechanisms easily and easy to maintain.

Example

Example of some components:

• TransformComponent: Describes the 3D world location.
• MeshComponent: Describes the associated mesh.
• Visible: Describes the visibility state.
• Hit: Event that notify this Entity got hit.

Tag or TagComponent

It's a Component but without data. It's used to mark and differentiate the Entities:

Example

• BlueTeam
• RedTeam
• Character
• Enemy

💡 Note that the tag component is not a special component type. The keyword exists just to give more flavour.

Databag

The Databag is a global piece of data, and it's used to store global utility information.

Example

List of some Databags:

• FrameTime: Databag where the frame delta and the physics_delta is stored.
• OsDatabag: Where it's stored some info about the OS (timestamp, platform, date).
• EngineDatabag: Where the engine details are stored.

World

The World is the container of all ECS data: Entities, Components, Databags.

System

The System is just a function that perform some operations on the World data. It manipulates (transform) the Entities, Components, Databags data. The System is defined by the user, and represent a piece of game logic.

Example

List of Systems:

• TimerSystem: Advances the timers clock till it expire.
• MoveSystem: Moves the Entity locations.

Query

The Query is used by the Systems to fetch the Components from the world; it returns the Entities that fulfills the request.

void timer_system(Query<TimerSystem> &p_query){}
void move_system(Query<Velocity, TransformComponent> &p_query){}
void heal_system(Query<Health, Heal, Maybe<ExtraHealPowerup>> &p_query){}
void damage_system(Query<Health, Damage, Without<Immunity>> &p_query){}

Storage

The Storage is the memory class used to store the components. There are different type of storages, each with a different set of features.

BatchStorage

Exactly like the Storage but allow to store more entries of the same Compnent per Entity. For example you can have an Entity with more Damage component.

Batch

The Batch is returned by the Query to give access to the Components stored in batches.

Event

The Event is a Component that at the end of each frame it's automatically destroyed. It's super useful to code one time messages or events. Useful to create mechanisms like:

• The damage mechanics.
• The healing mechanics.
• The hit mechanics.
• The enter/exit mechanics.
• The button click mechanics.