baking.md

Authoring components and Bakers

// An example component for which we want to
// define an authoring component and a baker.
public struct EnergyShield : IComponentData
{
    public int HitPoints;
    public int MaxHitPoints;
    public float RechargeDelay;
    public float RechargeRate;
}

// An authoring component for EnergyShield.
// By itself, an authoring component is just an ordinary MonoBehavior.
public class EnergyShieldAuthoring : MonoBehaviour
{
    // Notice the authoring component has no HitPoints field.
    // This is fine as long as we don't need to set the HitPoints
    // value in the editor.

    // The fact that these names mirror the fields
    // of EnergyShield is not a requirement.

    public int MaxHitPoints;
    public float RechargeDelay;
    public float RechargeRate;
}

// The baker for our EnergyShield authoring component.
// For every GameObject in an entity subscene, baking creates a
// corresponding entity. This baker is run once for every
// EnergyShieldAuthoring instance that's attached to any GameObject in
// the entity subscene.
public class EnergyShieldBaker : Baker<EnergyShieldAuthoring>
{
    public override void Bake(EnergyShieldAuthoring authoring)
    {
        // This simple baker adds just one component to the entity.
        AddComponent(new EnergyShield {
            HitPoints = authoring.MaxHitPoints,
            MaxHitPoints = authoring.MaxHitPoints,
            RechargeDelay =  authoring.RechargeDelay,
            RechargeRate = authoring.RechargeRate,
        });
    }
}

A Baker must register the data it accesses. For the authoring component, this is automatic, but for other data (assets, prefabs, and other GameObject components), you must access them through Baker methods to ensure the Baker is aware of them:

public struct MyComponent : IComponentData
{
    public int A;
    public float B;
    public Entity Prefab;
}

public class MyAuthoring : MonoBehaviour
{
    public GameObject prefab;
    public GameObject otherGO;
    public Mesh mesh;
}

public class MyBaker : Baker<MyAuthoring>
{
    public override void Bake(MyAuthoring authoring)
    {
        // To do this, use the functions that the Baker provides to access other components, instead of the ones provided by GameObject:
        // In the same way, if you access data from an asset, you need to create a dependency for it, so the Baker reruns if the asset changes.
        // We want to rebake if anything changes in the mesh itself

        var transform = GetComponent<Transform>(authoring.otherGO);
        DependsOn(authoring.mesh);
        AddComponent(new MyComponent
        {
            A = authoring.mesh.vertexCount,
            B = transform.position.x,
            Prefab = GetEntity(authoring.prefab)   // to register and convert Prefabs, call `GetEntity` in the baker:
        });
    }
}

Scene loading

In the Editor, the SceneSystem.GetSceneGUID method internally uses UnityEditor.AssetDatabase to map a scene path to a GUID. However, UnityEditor.AssetDatabase cannot be used in a standalone player, so a standalone player uses the "StreamingAssets/catalog.bin" file instead, which is produced in the build and is a table of paths mapped to GUID's.