Enum TransformUsageFlags

Controls how Transform components on GameObjects are converted to entity data.

Namespace: Unity.Entities

Assembly: Unity.Entities.Hybrid.dll

Syntax

[Flags]
public enum TransformUsageFlags

Remarks

These flags help to reduce the number of unnecessary transform components in baked entities based on their intended use at runtime.

The Dynamic flag replicates as close as possible the GameObject data and structure. These flags are used whenever an entity is requested during conversion, for example, via GetEntity(). Bakers for default GameObject components add the appropriate TransformUsageFlags too. For example, in the case of the baker for MeshRenderer, Renderable is added as a TransformUsageFlag.

More than one baker can indicate different TransformUsageFlags for the same entity. All those flags are combined together before the transform components are added to the entity. For example if a baker requests for an entity to be Dynamic and another baker requests for the same entity to be in WorldSpace, the entity is considered to be Dynamic and in WorldSpace when the transform components are added to the entity.

These are a few examples on how to use TransformUsageFlags can help to reduce the number of unnecessary transforms components on entities:

If you have a GameObject representing a building and that building contains a child GameObject that is a window (these entities aren't going to move at runtime). If both entities are only marked as Renderable, then they don't need to be in a hierarchy and all their transform information can be combined in a LocalToWorld component (in WorldSpace). In this case both entities only have a LocalToWorld component and they don't have LocalTransform and Parent unnecessarily.

In another example, the same window GameObject could be part of a ship instead of a building. In that case, the ship is marked as Dynamic and the window is still Renderable. The window entity ends up with all the required transform components to follow the ship around when it sails (LocalToWorld, LocalTransform and Parent).

A building GameObject could have a helicopter GameObject on the roof (as a child). In this case the building is still Renderable, but the helicopter is marked as Dynamic because it can take off. The helicopter has the transform components to be moved (LocalToWorld, LocalTransform), but it isn't parented to the building and its transform data is in world space.

In the case of a ship with a helicopter, both are marked as dynamic and the helicopter entity is a child of the ship, so it follows the ship around when it sails. In this particular case when the helicopter takes off, the hierarchy needs to be broken manually at runtime and the transform data converted to world space.

If the helicopter can shoot some bullets, the bullet entity prefab will automatically be marked as Dynamic so the instances can be placed in the world.

There is also a case where an Entity might be stripped out from the final world during baking. This happens when there is no baker adding a TransformUsageFlag to it (TranformUsageFlags.None counts as adding a TransformUsageFlag). An example of this is a GameObject that's created in the Editor Hierarchy to group their children at authoring time for organizational purposes, but has no use at runtime. In this case, the children are moved to world space. There is an exception to this stripping rule, if an entity that has no TransformUsageFlags has a Dynamic parent and Dynamic children, then that entity is considered Dynamic as well and it isn't stripped out.

Fields

Name	Description
Dynamic	Indicates that an entity requires the necessary transform components to be moved at runtime (LocalTransform, LocalToWorld).
ManualOverride	Indicates that you want to take full manual control over the transform conversion of an entity.
NonUniformScale	Indicates that an entity requires transform components to represent non uniform scale.
None	Specifies that the entity doesn't need transform components.
Renderable	Indicates that an entity requires the necessary transform components to be rendered (LocalToWorld), but it doesn't require the transform components needed to move the entity at runtime.
WorldSpace	Indicates that an entity needs to be in world space, even if they have a Dynamic entity as a parent.