Module threed 

Layered 2.5-D crowd locomotion for multi-storey environments.

In real buildings (stations, airports, malls, stadiums) pedestrians spend the vast majority of their time walking on a floor and only occasionally transition vertically via stairs, escalators, ramps, or lifts. Running full 3-D collision physics for every pedestrian all of the time is wasteful and numerically fragile.

The industry-standard approach (used by JuPedSim, MassMotion, Legion) is layered 2.5-D: each pedestrian lives on a floor (integer index) and its planar (x, y) motion is advanced by one of the 2-D models in the crate (Social Force by default). Vertical motion is scripted by the rustsim-mobility crate through FloorTransitions — the pedestrian reaches a connector, is placed on the next floor, and its planar state is preserved.

This module defines the data model:

• Pedestrian3D — 2-D pose plus floor index and vertical offset.
• WallPolygon3D — a polyline of 3-D segments, one per floor, used by renderers and per-floor-physics setup.
• FloorTransition — a connector (stair, escalator, ramp, lift) that maps a 2-D region on floor A to a 2-D region on floor B with an associated travel time.
• LayeredSpace — a container of floors, walls, and connectors.
• step_layered — advance every pedestrian by one tick, delegating per-floor motion to a provided 2-D model step function.

Structs

ActiveTransition

An active transition a pedestrian is currently riding.

FloorTransition

A connector between two floors.

LayeredScratch

Advance every pedestrian in peds by dt using planar_step as the per-floor physics and space for walls and connectors.

LayeredSpace

A multi-floor environment.

Pedestrian3D

A pedestrian in a layered 2.5-D environment.

WallPolygon3D

A polyline wall that spans a single floor.

Enums

ConnectorKind

Kind of vertical connector.

Traits

LayeredObserver

Per-pedestrian post-step observation hook for the layered 2.5-D drive.

Functions

step_layered

Advance every pedestrian in peds by dt. Convenience wrapper that allocates one LayeredScratch per call and immediately drops it; prefer step_layered_scratch when the same simulation drives successive ticks.

step_layered_scratch

Zero-allocation variant of step_layered.

step_layered_scratch_observed

Observed variant of step_layered_scratch: identical semantics, plus a post-tick callback for every pedestrian.

Type Aliases

FloorId

Integer floor index. 0 = ground floor, 1 = first floor, etc.

PlanarStepFn

Function that advances a slice of 2-D pedestrians on a single floor by dt.