Editing OpenSimulator Internals/Code Map/Scene (section)

== The Main Loop (Heartbeat) ==

The scene runs one thread: the Heartbeat thread. Started by Start():

 Heartbeat()
   TriggerOnRegionStarted()
   Update(1)  -- first frame, watchdog not yet active
   Watchdog alarm enabled
   Update(-1)  -- runs until shutdown

Update() loop runs once per frame:

Per frame (every frame unless noted):
# CheckTerrainUpdates() -- every 4 frames
# UpdateTerrain() -- every m_update_terrain frames (default 1000)
# UpdatePreparePhysics() -- physics pre-step
# SendCoarseLocations() -- every 5 frames, async via thread pool
# UpdatePhysics(FrameTime) -- main physics step, returns physicsFPS
# CheckAtTargets() -- check llMoveToTarget / llRotLookAt
# UpdateObjectGroups() -- send queued object updates to clients
# UpdatePresences() -- send presence updates to clients
# CleanTempObjects() -- every 180 frames, async
# UpdateEvents() -- fires EventManager.OnFrame
# UpdateStorageBackup() -- every 200 frames, async
# Frame 20: enable logins, inform neighbours region is up, set Ready=true, GC compact

Frame timing: FrameTime defaults to 0.0908s (~11fps). Sleep is calculated to hit target frame time. Stats normalized to 55fps for viewer display.

Backup runs asynchronously every 200 frames. Objects are only persisted if they have been changed for at least MinimumTimeBeforePersistenceConsidered (default 60s) and no longer than MaximumTimeBeforePersistenceConsidered (default 600s).

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