blob-asset-in-baker

Blob Asset in Baker

Intent

Build immutable, Burst-safe, shareable constant data blobs at bake time using BlobBuilder, register them with BlobAssetStore for lifetime management, and store BlobAssetReference in a runtime component.

Use When

Large constant data shared by multiple entities or per-entity (animation curves, config tables, mesh bounds, spell data, nav tables). Any read-only data that does not change at runtime and benefits from shared memory or Burst-safe access.

Avoid When

The data changes at runtime — blobs are immutable. Avoid for small scalar constants — just put them in the component directly. Avoid storing BlobArray by value outside of a BlobAssetReference.

Senior Pattern

• Define a struct with BlobArray, BlobString, or nested BlobPtr fields for the blob shape.
• In Baker: using var blobBuilder = new BlobBuilder(Allocator.Temp) — dispose scope ensures cleanup.
• ref var root = ref blobBuilder.ConstructRoot<MyBlobData>() — root allocation.
• var array = blobBuilder.Allocate(ref root.MyArray, count) — allocate BlobArray.
• blobBuilder.CreateBlobAssetReference<MyBlobData>(Allocator.Persistent) — create the reference.
• AddBlobAsset(ref blobRef, out _) — registers with BlobAssetStore, enables deduplication and lifetime management.
• Store BlobAssetReference<MyBlobData> in a component field.

Code Template

public struct AnimationBlobData
{
    public BlobArray<float> Keyframes;
    public float Duration;
    public int FrameCount;
}

class Baker : Baker<AnimationAuthoring>
{
    public override void Bake(AnimationAuthoring authoring)
    {
        DependsOn(authoring.AnimationCurve);  // register dependency first

        var entity = GetEntity(TransformUsageFlags.Dynamic);

        using var builder = new BlobBuilder(Allocator.Temp);
        ref var root = ref builder.ConstructRoot<AnimationBlobData>();
        root.Duration = authoring.AnimationCurve.length > 0
            ? authoring.AnimationCurve.keys[^1].time : 0f;
        root.FrameCount = authoring.AnimationCurve.length;

        var keyframes = builder.Allocate(ref root.Keyframes, root.FrameCount);
        for (int i = 0; i < root.FrameCount; i++)
            keyframes[i] = authoring.AnimationCurve.keys[i].value;

        var blobRef = builder.CreateBlobAssetReference<AnimationBlobData>(Allocator.Persistent);
        AddBlobAsset(ref blobRef, out _);

        AddComponent(entity, new AnimationData { Blob = blobRef });
    }
}