iw4L/docs/ENTITIES.md

World entities and the funnel

There is one funnel

human ─┐
bot    ├─→ TickInput ─→ sim::step ─→ Snapshot ─→ client / theater / demo
replay ┘

pub fn step(world: &mut SimWorld, tick: Tick, input: &TickInput,
            msec: i32, reason: StepReason) -> Snapshot;

Headless, prediction and replay call exactly this one. msec is the step length; time enters only as an argument. The shape of the funnel is SIM-STEP.md, the code crates/sim/src/lib.rs.

What can be an entity at all — fixed by the data (entity_iw4)

The wiring is ours, the taxonomy comes with the data. The crate neither serializes nor orders fields "for the network": it pins the layout it reads, and leaves transport to net.

EntityState	replicated snapshot slot, stride 0x100
Centity	client-side slot, stride 0x204 (pose plus snapshot anchors)
ClientState	per-client slot, stride 0x7c (command, name[16])
CorpseInfo	server-side corpse slot, stride 0x53c, 8 of them
ET_PLAYER / ET_PLAYER_CORPSE / ET_ITEM / ET_MISSILE
Trajectory	evaluate_trajectory: gravity 400, delta 800
events	the entity-event ring, an 11-bit wrapper
ENTITYNUM_NONE	0x7FF
playerstate_iw4	player and input: the two ends of the funnel

Where everything else lives

• sim/ — gentity spawn world snapshot damage bullet* missile item corpse match_state score rules world_objects identities (ScriptModelId is the one identity of a script model; a raw u32 is not a second one);
• frame — AppScreen, RuntimeRole, LaunchIdentity and ScopePlugin: match/round states, scoped resource registration and entity retirement;
• session — standing the match up and tearing it down through ScopeControl; net — wire, deltas, prediction; bots — host-only controllers that observe through a sensor adapter, walk a ClipMap-baked graph and enter the same TickInput.

net/transport/meta_wire.rs encodes and parses metadata messages. The pure world_object_wire.rs codec validates complete world-object updates; world_sync.rs owns mutable baselines and periodic full synchronization. Frame decoding commits its prepared world update after reliable and service sections succeed, so a refused frame leaves the world baseline intact.

Snapshots publish the semantics of DObj composition, never runtime trees or posed vertices (ANIM.md).