World Streaming core concepts

This chapter defines the vocabulary used throughout the World Streaming handbook. For the shortest path to a working level, see Getting started.

Data flow

flowchart LR author["Editor authoring
WorldConfig + partition view"] --> wsworld[".wsworld + shard Prefabs"] wsworld --> ap["Asset Processor
PrefabProcessor + aggregator"] ap --> manifest[".wsmanifest"] ap --> spawnables["Cell / HLOD Spawnables"] manifest --> runtime["WorldStreamingSystemComponent"] spawnables --> runtime sources["Streaming sources"] --> runtime runtime --> world["On-demand Loaded / Activated world"]

Authoring writes WorldConfig and shard Prefabs; bake produces a Manifest and per-cell Spawnables; runtime resolves desired cell states from streaming sources within budgets.

Cell and Grid

Term	Meaning
Cell	Smallest streaming unit. Logical key is `WorldStreamingCellCoord` (x, y, z, gridLevel, layerId); stable hash is `WorldStreamingCellId` (includes `cellIdSalt`). Each content cell maps to one Spawnable.
Grid	A set of equal-size cells. You can declare multiple grid levels (finer = smaller `m_cellSize`, typically lower `m_gridLevel`). Optional vertical (Z) partitioning uses `m_verticalPartitioning` + `m_cellSizeZ`.
AlwaysLoaded	Non-spatial cell for entities with `IsSpatiallyLoaded = false`. Always resident when their Content Layer allows it; still gated by layer state.

Default cell size is 128 m. Changing cell size, origin (m_gridOriginD), or salt repartitions the world—regenerate cellIdSalt and rebake. See Authoring.

Loaded vs Activated

World Streaming uses a two-tier residency model:

State	Meaning
Unloaded	Not in memory
Loaded	Entities resident; no simulation / rendering (warmup)
Activated	Entities active for simulation and rendering
Failed	Load failed; retries with exponential backoff

Unloaded → Loading → Loaded → Activating → Activated
 ↑ |
 └── Deactivating ←───────────┘
Loaded → Unloading → Unloaded

Load Radius drives the Loaded ring around a streaming source.
Activate Radius drives the Activated ring (usually smaller).
Unload and deactivate apply hysteresis and cooldown so cells do not thrash at boundaries.

Render-origin switches do not change desired cell state: resolution uses absolute world distance (double-precision friendly). Streaming sources prefer HighPrecisionTransformBus double translation.

Streaming sources

A streaming source is an interest point that contributes to the desired cell set:

Form	Model	Typical use
`WorldStreamingStreamingSourceComponent`	Push	Player, camera
Script `RegisterStreamingSource`	Push (handle; cleared on world unload)	Portal preheat, scripted zones
`WorldStreamingStreamingSourceProviderRequestBus`	Pull	Cinematic cameras, AI / server interest

Multiple sources merge (Include) or carve (Exclude). Field-level detail: Runtime streaming.

Manifest and `.wsworld`

Asset	Role
`.wsworld`	Authoring descriptor: aggregation source list, optional `m_chunkSize` / `m_shardSize`, Loaded Regions are editor-only and never enter the runtime Manifest.
`.wsmanifest`	Runtime schedule: cell layout, dependencies, HLOD, `contentHash` for multiplayer handshake.
`.wschunk`	Optional Manifest chunk when the world exceeds chunk thresholds—lazy metadata for huge worlds.

Root Spawnable stays light; world content streams through the Manifest. Details: Baking.

Content Layers and HLOD

Content Layer: logical group across cells with runtime tri-state Unloaded / Loaded / Activated. Child effective state is clamped by ancestors (min). Use for quest phases, day/night sets, client-only or server-only content. See Content Layers.
HLOD: distant proxy cells generated at bake time. When child content activates, matching proxy regions hide; on unload, proxies appear before content unloads. Mesh show/hide in Atom usually needs Bridge/AtomMode = Bridge. See HLOD.

Editor shard vs server shard

These share the word “shard” but mean different things:

Kind	What it is	Configured by
Editor shard	Collaboration Prefab split of cell content (AutoShard, sub-shards, per-actor sidecars)	Partition view / editor tools
Server shard	Multi-authority server ownership index over the world	`.wsworld` `m_shardSize` + `OwnedShardCoords`

Do not confuse the two when reading multiplayer docs. See Authoring and Multiplayer.

Gem modules

World Streaming is one Gem with optional build targets:

Target	Role
`WorldStreaming`	Runtime core (AzCore / AzFramework only; dedicated-server friendly)
`WorldStreaming.Editor` / `.Builders`	Partition UI and bake pipeline
`WorldStreaming.Multiplayer`	Optional interest sync and authority
`WorldStreaming.TerrainVegBridge` / `.NavMeshBridge` / `.AtomBridge`	Optional subsystem bridges
`WorldStreaming.Debug`	Optional ImGui diagnostics

Next steps

Authoring: place content and configure the partition view.
Runtime streaming: how sources resolve desired state.
Reference: component field tables.