Companion to the Phase 6.6 UpdateMotion parser. Without this, every
server-spawned entity stays frozen at its CreateObject origin forever
— NPCs don't patrol, creatures don't hunt, other players don't walk
past. UpdatePosition is the per-entity position delta the server sends
on every movement tick.
The wire format is straightforward but fiddly:
u32 opcode | u32 guid | u32 flags | u32 cellId | 3xf32 pos
(0..4) conditional f32 rotation components, present iff the
corresponding OrientationHasNo* flag is CLEAR
optional 3xf32 velocity iff HasVelocity
optional u32 placementId iff HasPlacementID
four u16 sequence numbers (consumed but not used)
Layout ported from references/ACE/Source/ACE.Server/Network/Structure/
PositionPack.cs::Write and ACE.Entity/Enum/PositionFlags.cs.
WorldSession dispatches PositionUpdated(guid, position, velocity) on
a successful parse. GameWindow wiring (guid → WorldEntity lookup and
transform swap) is deferred to the same follow-up commit that lands
Phase 6.6 wiring, after the in-flight Phase 9.1 translucent-pass work
merges so we don't step on GameWindow.cs edits.
96 Core.Net tests (was 89, +7 for UpdatePosition coverage).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
333a7c197a